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INTRODUCTION Trial of labor (TOLAC) is an option in most preganancies after a cesarean section The objective of the study was to compare perinatal outcome in TOLAC and non-TOLAC deliveries in a population with high TOLAC rates. MATERIAL AND METHODS This was a cohort study based on population data from the Medical Birth Registry of Norway. We included term, cephalic, single, second deliveries, 1989-2009, after a first cesarean section (n = 43 422). TOLAC, TOLAC failure, non-TOLAC deliveries, and after high-risk and low-risk pregnancies (no risk/any risk), were compared with respect to offspring mortality, 5-minute Apgar score Apgar

Introduction: In pregnancies after a previous cesarean section (CS), a planned repeat CS delivery has been associated with excess risk of adverse outcome. However, also the alternative, a trial of labor after CS (TOLAC), has been associated with excess risks. A TOLAC failure, involving a non-planned CS, carries the highest risk of adverse outcome and a vaginal delivery the lowest. Thus, the decision regarding delivery mode is pivotal in clinical handling of these pregnancies. However, even with a high TOLAC rate, as seen in Norway, repeat CSs are regularly performed for no apparent medical reason. The objective of the present study was to assess to which extent demographic, socioeconomic, and health system factors are determinants of TOLAC and TOLAC failure in low risk pregnancies, and whether any effects observed changed with time. Materials and methods: The study group comprised 24 645 second deliveries (1989–2014) after a first delivery CS. Thus, none of the women had prior vaginal deliveries or more than one CS. Included pregnancies were low risk, cephalic, single, and had gestational age ≥ 37 weeks. Data were obtained from the Medical Birth Registry of Norway (MBRN). The exposure variables were (second delivery) maternal age, length of maternal education, maternal country of origin, size of the delivery unit, health region (South-East, West, Mid, North), and maternal county of residence. The outcomes were TOLAC and TOLAC failure, as rates (%), relative risk (RR) and relative risk adjusted (ARR). Changes in determinant effects over time were assessed by comparing rates in two periods, 1989–2002 vs 2003–2014, and including these periods in an interaction model. Results: The TOLAC rate was 74.9%, with a TOLAC failure rate of 16.2%, resulting in a vaginal birth rate of 62.8%. Low TOLAC rates were observed at high maternal age and in women from East Asia or Latin America. High TOLAC failure rates were observed at high maternal age, in women with less than 11 years of education, and in women of non-western origin. The effects of health system factors, i.e. delivery unit size and administrative region were considerable, on both TOLAC and TOLAC failure. The effects of several determinants changed significantly (P < 0.05) from 1989–2002 to 2003–2014: The association between non-TOLAC and maternal age > 39 years became weaker, the association between short education and TOLAC failure became stronger, and the association between TOLAC failure and small size of delivery unit became stronger. Conclusion: Low maternal age, high education, and western country of origin were associated with high TOLAC rates, and low TOLAC failure rates. Maternity unit characteristics (size and region) contributed with effects on the same level as individual determinants studied. Temporal changes were observed in determinant effects. publishedVersion

Background Socioeconomic (SE) inequalities have been observed in a number of adverse outcomes of pregnancy and many of the risk factors for such outcomes are associated with a low SE level. However, SE inequalities persist even after adjustment for these risk factors. Less well-off women are more vulnerable, but may also get less adequate health services. The objective of the present study was to assess possible associations between SE conditions in terms of maternal education as well as ethnic background and obstetric care. Methods A population-based national cohort study from the Medical Birth Registry of Norway. The study population comprised 2 305 780 births from the observation period 1967–2009. Multilevel analysis was used because of the hierarchical structure of the data. Outcome variables included induction of labour, epidural analgesia, caesarean section, neonatal intensive care and perinatal death. Results While medical interventions in the 1970s were employed less frequently in women of short education and non-western immigrants, this difference was eliminated or even reversed towards the end of the observation period. However, an excess perinatal mortality in both the short-educated [adjusted relative risk (aRR) = 2.49] and the non-western immigrant groups (aRR = 1.75) remained and may indicate increasing health problems in these groups. Conclusion Even though our study suggests a fair and favourable development during the last decades in the distribution across SE groups of obstetric health services, the results suggest that the needs for obstetric care have increased in vulnerable groups, requiring a closer follow-up.

Hypertensive disorders of pregnancy (HDP) tend to recur from one pregnancy to the next. The aims of the study were to assess the recurrence risk according to type of HDP defined by gestational age at birth and to examine whether recurrence is associated with the following additional risk factors for HDP: maternal age, smoking, inter delivery interval, diabetes, body mass index, as well as fetal growth restriction, and to assess temporal trends in these associations. All women with two singleton births in the Medical Birth Registry of Norway 1967-2012 (n= 742 980) were included in this population based cohort study. Logistic regression was used to calculate odds ratios for the risk of recurrent HDP according to type of HDP. The highest odds ratio of recurrence was observed for the same type of HDP based on gestational age at delivery. After gestational hypertension and term preeclampsia the risk increased tenfold for the same type to recur, whereas after late and early preterm preeclampsia, the risk increased 27 and 97 fold, respectively. The recurrence of early preterm preeclampsia was less influenced by additional risk factors than term HDP. Recurrence of early preterm HDP was significantly lower from 1993 onwards. Recurrent HDP tended to be of the same type as the previous HDP. Risk of recurrence associated with additional risk factors were observed particularly after term. The odds ratio of recurrence of early preterm HDP was significantly lower from 1993 onwards. This article is protected by copyright. All rights reserved.

INTRODUCTION In most pregnancies after a cesarean section, a trial of labor is an option. The objective of the study was to explore trial of labor and its failure in pregnancies with medical risk conditions, in a population with a high trial of labor rate. MATERIAL AND METHODS In a cohort study (n = 57 109), using data from the Medical Birth Registry of Norway 1989-2014, women with a second delivery after a first pregnancy cesarean section were included. Preterm, multiple, and non-cephalic deliveries were excluded. The outcomes were trial of labor and failed trial of labor, assessed as rates and relative risk, using deliveries without risk conditions as reference. Temporal trends were assessed by 3-year periods. The exposures were selected medical risk conditions, ie previous offspring death, labor dystocia, diabetes, heart conditions, chronic hypertension, chronic kidney disease, rheumatoid arthritis, thyroid disease, asthma, prepregnancy psychiatric conditions, epilepsy, obesity, gestational diabetes, eclampsia and preeclampsia, gestational hypertension, major malformations, second-pregnancy psychiatric conditions, assisted reproduction, macrosomia, and small-for-gestational-age neonates. Induced onset of labor was compared with spontaneous onset of labor for each condition studied. RESULTS In risk pregnancies (n = 31 994) the trial of labor rate was 64.9% and failure rate was 27.6%, compared with 74.6% and 16.4% in pregnancies without any of the risk conditions studied (n = 25 115). The lowest trial of labor rates were observed in diabetes type 1 (49.5%), diabetes type 2 (46.7%), maternal heart conditions (54.5%), and pregnancy-related psychiatric conditions (19.7%). The highest failure rates were observed in diabetes type 1 (43.1%), diabetes type 2 (40.3%), maternal obesity (36.9%), gestational diabetes (36.0%), and offspring macrosomia (43.0%). Induced labor was associated with failed trial of labor (P

Combining work and family responsibilities is challenging when children have special needs, and mothers commonly make employment-related adjustments. In this study, the authors examined associations between maternal work absence and child language impairment and behavior problems in preschool children. Questionnaire data at child age 3 years from 33,778 mothers participating in the prospective population-based Norwegian Mother and Child Cohort Study were linked to national register data on employment and long-term physician-certified sick leave at child age 3-5 years. Mothers who reported having a child with language impairment had a consistently higher risk of not being employed and were at increased risk of taking long-term sick leave at child age 5 years. Co-occurring problems were associated with excess risk. Language impairments in preschool children, in particular when they are co-occurring with behavior problems, are likely to have a range of negative short- and long-term consequences for the financial and overall health and well-being of mothers and their families.

BACKGROUND The purpose of this study was to investigate breastfeeding as a health indicator through routine data registered at public child health centres. The prevalence and course of breastfeeding were surveyed, as well as factors that affect breastfeeding. MATERIAL AND METHOD Breastfeeding status at six weeks and six months of age and other routine data were systematically recorded in a newly developed electronic medical records system (Health Profile 0-20 years) for infants attending public child health centres in Bergen in the period 2010-11. This information was linked to data from the Medical Birth Registry. RESULTS Of 6,093 infants, 73.6% were exclusively breastfed at six weeks of age and 18.9% at six months. In adjusted analyses, there was an association between breastfeeding cessation before six months and the factors smoking, low maternal age, marital status as single, unsatisfactory family situation and social network, and birth weight under 2,500 g. Attendance at a specialist breastfeeding centre and uncertain/abnormal sleep patterns in infants were associated with continued breastfeeding after six months. INTERPRETATION The medical records system «Health Profile 0-20 years», linked to the Medical Birth Registry, was well suited to studying factors that can affect breastfeeding. Mothers and infants with increased need for follow-up were identified.

Background: Perinatal mortality according to birth weight has an inverse J-pattern. Our aim was to estimate the influence of familial factors on this pattern, applying a cohort sibling design. We focused on excess mortality among macrosomic infants (>2 SD above the mean) and hypothesized that the birth weight-mortality association could be explained by confounding shared family factors. We also estimated how the participant’s deviation from mean sibling birth weight influenced the association. Methods and findings: We included 1 925 929 singletons, born term or post-term to mothers with more than one delivery 1967–2011 registered in the Medical Birth Registry of Norway. We examined z-score birth weight and perinatal mortality in random-effects and sibling fixed-effects logistic regression models including measured confounders (e.g. maternal diabetes) as well as unmeasured shared family confounders (through fixed effects models). Birth weight-specific mortality showed an inverse J-pattern, being lowest (2.0 per 1000) at reference weight (z-score +1 to +2) and increasing for higher weights. Mortality in the highest weight category was 15-fold higher than reference. This pattern changed little in multivariable models. Deviance from mean sibling birth weight modified the mortality pattern across the birth weight spectrum: small and medium-sized infants had increased mortality when being smaller than their siblings, and large-sized infants had an increased risk when outweighing their siblings. Maternal diabetes and birth weight acted in a synergistic fashion with mortality among macrosomic infants in diabetic pregnancies in excess of what would be expected for additive effects. Conclusions: The inverse J-pattern between birth weight and mortality is not explained by measured confounders or unmeasured shared family factors. Infants are at particularly high mortality risk when their birth weight deviates substantially from their siblings. Sensitivity analysis suggests that characteristics related to maternal diabetes could be important in explaining the increased mortality among macrosomic infants. publishedVersion

Objective To assess whether the reported excess of large for gestational age (LGA) neonates in pre-eclamptic women delivering at term is attributable to maternal obesity. Design, setting and population Population-based observational study including 77 294 singleton pregnancies registered in the Medical Birth Registry of Norway between 2007 and 2010. Methods Comparison of birthweight percentiles and z-scores between women with and without pre-eclampsia. Main outcome measures Odds ratio (OR) of LGA and z-scores of birthweight in relation to pre-eclampsia. Results Pre-eclamptic women delivering at term had increased risk of having LGA neonates. Unadjusted ORs with 95% confidence interval (95% CI) of LGA above the 90th and 95th birthweight centiles were 1.4, 95% CI 1.2–1.6 and 1.6, 95% CI 1.3–1.9, respectively. The excess of LGA persisted after including gestational diabetes and diabetes types 1 and 2 in a multivariate analysis (corresponding ORs 1.3, 95% CI 1.1–1.5 and 1.4, 95% CI 1.2–1.7), but disappeared after adjusting for maternal prepregnant body mass index (ORs 1.1, 95% CI 0.9–1.2 and 1.1, 95% CI 0.9–1.3). Conclusions This study suggests accelerated fetal growth in a subset of pre-eclamptic women delivering at term. The excess of LGA neonates is attributable to maternal obesity among pre-eclamptic women delivering at term. The maternal obesity epidemic may lead to an increased prevalence of both pre-eclampsia and LGA neonates among women delivering at term.

This study explores the stability and change in maternal life satisfaction and psychological distress following the birth of a child with a congenital anomaly using 5 assessments from the Norwegian Mother and Child Cohort Study collected from Pregnancy Week 17 to 36 months postpartum. Participating mothers were divided into those having infants with (a) Down syndrome (DS; n = 114), (b) cleft lip/palate (CLP; n = 179), and (c) no disability (ND; n = 99,122). Responses on the Satisfaction With Life Scale and a short version of the Hopkins Symptom Checklist were analyzed using structural equation modeling, including latent growth curves. Satisfaction and distress levels were highly diverse in the sample, but fairly stable over time (retest correlations: .47-.68). However, the birth of a child with DS was associated with a rapid decrease in maternal life satisfaction and a corresponding increase in psychological distress observed between pregnancy and 6 months postpartum. The unique effects from DS on changes in satisfaction (Cohen's d = -.66) and distress (Cohen's d = .60) remained stable. Higher distress and lower life satisfaction at later assessments appeared to reflect a persistent burden that was already experienced 6 months after birth. CLP had a temporary impact (Cohen's d = .29) on maternal distress at 6 months. However, the overall trajectories did not differ between CLP and ND mothers. In sum, the birth of a child with DS influences maternal psychological distress and life satisfaction throughout the toddler period, whereas a curable condition like CLP has only a minor temporary effect on maternal psychological distress. (PsycINFO Database Record (c) 2014 APA, all rights reserved).

We aimed to explore why, in population studies, the positive association between normal-range birth weight and intelligence becomes negative at the highest birth weights. The study population comprised 217,746 Norwegian male singletons born at term between 1967 and 1976. All had data on birth weight and intelligence quotient (IQ) score at the time of military conscription; 137,574 had data on sibling birth weights; and 62,906 had data on male sibling birth weights. We estimated associations between birth weight and IQ score by ordinary least squares regression for the total study population and by fixed-effects regression for comparisons of brothers. The crude mean IQ score was 1.2 points (95% confidence interval (CI): 0.3, 2.2) lower for those with birth weights of 5,000 g or more compared with the reference group (with birth weights of 4,000-4,499 g). This difference leveled off to 0.0 (95% CI: -0.8, 0.9) in multivariable ordinary least squares regression and reversed to 2.2 points (95% CI: 0.3, 4.2) higher in fixed-effects regression. Results differed mainly because, at a given birth weight, participants who had a sibling with macrosomia had a lower mean IQ score. Nevertheless, within families with 1 or more macrosomic siblings, as in other families, men with higher birth weights tended to have higher IQ scores. Thus, a family-level confounder introduces a cross-level bias that cannot be detected in individual-level studies. We suggest ways in which future studies might elucidate the nature of this confounder.

Background Many women temporarily reduce work hours or stop working when caring for small children. However, mothers of children with special health care needs may face particular challenges balancing childrearing responsibilities and employment demands. This study examines how the work participation among mothers of children with special health care needs compares with that of mothers in general during early motherhood, focusing in particular on the extent of the child's additional health care needs. Methods By linkage of the population-based Norwegian Mother and Child Cohort Study with national registers on employment, child health care needs, and social background factors, 41 255 mothers employed prior to childbirth were followed until child age 3 years to investigate associations between the child's care needs and mother's dropping out of employment. Results In total, 16.3% of the formerly employed mothers were no longer employed at child age 3 years. Mothers of children with mild care needs did not differ from mothers in general, whereas mothers of children with moderate [Risk Ratio (RR) 1.45; 95% confidence interval (CI) 1.17, 1.80] and severe care needs [RR 2.19; 95% CI 1.67, 2.87] were at substantial risk of not being employed at follow-up. The impact of the child's health care needs remained strong also after adjusting for several factors associated with employment in general. Conclusions Extensive childhood health care needs are associated with reduced short-term employment prospects and remain a substantial influence on mothers' work participation during early motherhood, irrespective of other important characteristics associated with maternal employment.

Objective To investigate the aggregation of obstetric anal sphincter injuries (OASIS) in relatives. Design Population-based cohort study. Setting The Medical Birth Registry of Norway from 1967 to 2008. Population All singleton, vertex-presenting infants weighing 500 g or more. Through linkage by national identification numbers, 393 856 mother–daughter pairs, 264 675 mother–son pairs, 134 889 mothers whose sisters later became mothers, 132 742 fathers whose brothers later became fathers, 131 702 mothers whose brothers later became fathers and 88 557 fathers whose sisters later became mothers were provided. Methods Comparison of women with and without a history of OASIS in their relatives. Main outcome measure Relative risk of OASIS after a previous OASIS in the family. Results The risk of OASIS was increased if the woman's mother or sister had OASIS in a delivery (aRR 1.9, 95% CI 1.6–2.3; aRR 1.7, 95% CI 1.6–1.7, respectively). If OASIS occurred in one brother's partner at delivery, the risk of OASIS in the next brother's partner was modestly increased (aRR 1.2, 95% CI 1.1–1.4). If OASIS occurred in one sister at delivery, the risk of OASIS in the brother's partner was also increased a little (aRR 1.2, 95% CI 1.1–1.4). However, there was no excess occurrence in sisters whose brothers' partners had previously had OASIS (aRR 1.1, 95% CI 0.9–1.3). Conclusions There appears to be increased familial aggregation of OASIS. These risks are stronger through the maternal rather than the paternal line of transmission, suggesting a strong genetic role that shapes aggregation of OASIS within families. These observations must be cautiously interpreted because of bias from unmeasured confounding factors may have impacted the findings.

Summary Background and objectives Women with preeclampsia have increased risk of developing ESRD. This study assessed whether this can be explained by preeclampsia itself or by familial aggregation of common risk factors. Design, setting, participants, & measurements Since 1967, the Medical Birth Registry of Norway has registered data on all births in the country. By linkage with the Norwegian Population Registry, different, but overlapping, cohorts were defined: the first and second cohorts included women and a sibling (first cohort) or child (second cohort) with a registered first birth between 1967 and 2008. Similar cohorts were defined for men. The Norwegian Renal Registry provided data on ESRD from 1980 to June 2009. Results Cohort 1 was used for the main analyses and included 570,675 women, 291 of whom developed ESRD after a median 18.2 years. Compared with women without preeclampsia and no siblings with preeclampsia, women without preeclampsia but a sibling with preeclampsia had a relative risk (RR) of ESRD of 0.96 (95% confidenceinterval,0.59–1.6),womenwithpreeclampsiabut nosiblingswithpreeclampsia hadaRR of6.0 (4.4– 8.1), and women with preeclampsia and a sibling with preeclampsia had a RR of 2.8 (0.88–8.6). Further analyses of women showed no increased risk of ESRD if a child had preeclampsia in first pregnancy. Conclusions FamilialaggregationofriskfactorsdoesnotseemtoexplainincreasedESRDriskafterpreeclampsia. These findings support the hypothesis that preeclampsia per se may lead to kidney damage. Clin J Am Soc Nephrol 7: 1819–1826, 2012. doi: 10.2215/CJN.01820212

Introduction Trial of labor (TOL) is an option in most deliveries after a previous cesarean section (CS). The Medical Birth Registry of Norway (MBRN) has received compulsory notification of all deliveries in the country since 1967, including data that could identify TOL in epidemiologic research. The objective of this study was to validate MBRN data for identification of TOL deliveries after a previous cesarean section (CS). Material and methods The MBRN provided a random national sample of 500 birth order two deliveries during 1989–2012 in women with a registered birth order one CS delivery. The reporting maternity units were asked to complete a questionnaire on data items in both deliveries, using hospital record data as the gold standard. Results Completed questionnaires were returned for 477 women (95.5%) with data on both deliveries. An algorithm to identify TOL using MBRN data from the birth order two delivery had a positive predictive value of 93.2%, a negative predictive value of 93.5%, a sensitivity of 96.1%, and a specificity of 88.8%. Validity of MBRN data on mode and onset of delivery, CS subtype, and planned mode of delivery is also reported. Conclusions MBRN data on planned and actual mode of delivery, CS subtype, and the algorithm to identify TOL in deliveries after a previous CS had satisfactory quality for a registry-based study of TOL.

Aims: Preterm birth is a major cause of perinatal mortality and morbidity and is strongly associated with socio-economic factors. The objective of this study was to examine the associations of maternal education, marital status and ethnicity with preterm birth and to determine the extent to which such associations can be explained by the established risk factors of maternal age, parity and smoking. Methods: This was a register-based cohort study with data from the Medical Birth Registry of Norway 1999–2009 and Statistics Norway. The sample included all singleton spontaneous births in Norway from 1999 to 2009 ( n=494,073). The main outcome measure was preterm birth (gestational age

To assess parity in women with chronic inflammatory arthritides (CIA) childless at time of diagnosis.Patients were selected from the Norwegian Disease-Modifying Anti-Rheumatic Drug (NOR-DMARD) registry. Each patient was matched by year of birth with 100 reference women from the Norwegian Population Registry. Data linkage for patients and references with the Medical Birth Registry of Norway (MBRN) identified all offspring until time of linkage (October 2007). Patients and corresponding references childless at the time of diagnosis were included in the analyses. Kaplan-Meier curves visualized the proportion of childless women and were compared by a log rank test.In all, 156 rheumatoid arthritis (RA), 107 other chronic arthritides (OCA), and 75 juvenile idiopathic arthritis (JIA) patients were childless at time of diagnosis. At the time of data linkage, the proportions (%) of childless RA/OCA/JIA patients versus references were 61.5/62.6/57.3 versus 46.9/42.9/41.0, respectively, all differences statistically significant. The log rank test showed lower parity in all diagnostic groups compared with references (p0.001 for RA and OCA and p = 0.002 for JIA). No difference in parity was observed between RA and OCA patients, but both diagnostic groups had lower parity than JIA patients (p = 0.001). Disease characteristics were similar between childless and fertile patients.Reduced parity was observed in all diagnostic groups compared with references. RA and OCA patients had lower parity than JIA patients, indicating that having the disease as a young adult may influence parity more than having the disease in childhood.

Pre-eclampsia is a leading complication of pregnancy, associated with maternal and neonatal morbidity. The present study describes the epidemiology of pre-eclampsia in Norway, with data from the Medical Birth Registry of Norway, covering 40 years. We aimed at describing time trends in prevalence, selected risk factors and perinatal mortality. We also analysed time trends in recurrence risk of total pre-eclampsia and pre-eclampsia with preterm delivery. A total of 2,416,501 women giving birth during 1967-2008 were included. Prevalence of pre-eclampsia increased from 1967 to 1999 and decreased thereafter, with an overall prevalence of 3%. Rates increased more over time among younger than older women, resulting in a significantly lower excess risk of pre-eclampsia associated with high maternal age in later years. For example, relative risk (RR) of pre-eclampsia among primiparae aged ≥35 relative to

Aim: To examine the predictive value of early assessments on developmental outcome at 5 years in children born extremely preterm. Methods: This is a prospective observational study of all infants born in Norway in 1999–2000 with gestational age (GA)

Please cite this paper as: Baghestan E, Irgens L, Bordahl P, Rasmussen S. Risk of recurrence and subsequent delivery after obstetric anal sphincter injuries. BJOG 2012;119:62–69. Objective To investigate the recurrence risk, the likelihood of having further deliveries and mode of delivery after third to fourth degree obstetric anal sphincter injuries (OASIS). Design Population-based cohort study. Setting The Medical Birth Registry of Norway. Population A cohort of 828 864 mothers with singleton, vertex-presenting infants, weighing 500 g or more, during the period 1967–2004. Methods Comparison of women with and without a history of OASIS with respect to the occurrence of OASIS, subsequent delivery rate and planned caesarean rate. Main outcome measures OASIS in second and third deliveries, subsequent delivery rate and mode of delivery. Results Adjusted odds ratios of the recurrence of OASIS in women with a history of OASIS in the first, and in both the first and second deliveries, were 4.2 (95% CI 3.9–4.5; 5.6%) and 10.6 (95% CI 6.2–18.1; 9.5%), respectively, relative to women without a history of OASIS. Instrumental deliveries, in particular forceps deliveries, birthweights of 3500 g or more and large maternity units were associated with a recurrence of OASIS. Instrumental delivery did not further increase the excess recurrence risk associated with high birthweight. A man who fathered a child whose delivery was complicated by OASIS was more likely to father another child whose delivery was complicated by OASIS in another woman who gave birth in the same maternity unit (adjusted OR 2.1; 95% CI 1.2–3.7; 5.6%). However, if the deliveries took place in different maternity units, the recurrence risk was not significantly increased (OR 1.3; 95% CI 0.8–2.1; 4.4%). The subsequent delivery rate was not different in women with and without previous OASIS, whereas women with a previous OASIS were more often scheduled to caesarean delivery. Conclusion Recurrence risks in second and third deliveries were high. A history of OASIS had little or no impact on the rates of subsequent deliveries. Women with previous OASIS were delivered more frequently by planned caesarean delivery.

OBJECTIVE: To assess whether premature rupture of membranes (PROM) is associated with placental abruption. DESIGN: Population-based study. SETTING: Data were extracted from the Medical Birth Registry of Norway. POPULATION: All women with PROM (18,889 cases), including 3,077 cases of preterm premature rupture of membranes (p-PROM), among a total of 355 416 singleton births in Norway during 1999-2005 with gestational age 17-44 weeks. METHODS: Logistic regression was used to assess whether placental abruption was associated with PROM in preterm and term births. MAIN OUTCOME MEASURES: Placental abruption. RESULTS: The occurrence of placental abruption in p-PROM was higher than in the total study population, 11.0 per 1,000 (34 of 3 077) vs. 4.2 per 1 000 (1 495 of 355 416; adjusted odds ratio 2.6, 95% confidence interval 1.8-3.7). Restricting the analyses to preterm births, the occurrence of placental abruption was less in p-PROM (11.0 per 1,000) than in births without p-PROM (36.1 per 1 000; adjusted odds ratio 0.3, 95% confidence interval 0.2-0.4). In term births, no statistically significant association was observed. CONCLUSIONS: The findings suggest that in p-PROM the risk of placental abruption is not higher than in other preterm births; rather the opposite. However, comparing the risks in p-PROM and the total gestational age range, the present study confirmed results reported in previous studies of a higher risk of placental abruption in p-PROM than in the total birth population.

Cerebral palsy (CP) is still the most common cause of chronic motor disability in hildhood. Until now, there has not been any previous national study of the anorama of subtypes, severity or risk factors among children with CP in Norway. his is a population based study of a cohort of children with CP born 1996 to 1998 in orway. These children are recorded in the Cerebral Palsy Register of Norway. The P definition and classification system agreed on by the Surveillance of Cerebral alsy in Europe (SCPE) are applied. The study showed that the prevalence of CP in orway was 2.1 per 1000 live births, comparable with other similar populations. Most children were classified in the spastic bilateral subtype (49%), about ne third (33%) in the spastic unilateral subtype and less than 10% in the dyskinetic r in the ataxic subtype. Both the distribution of subtypes and gross motor function impairments were comparable with other populations in developed countries. More children in our study had fine motor function impairments, as well as associated impairments. The associated impairments included both impairment of speech and feeding, in addition to impairments of vision, hearing, cognition and presence of active epilepsy. We identified both breech presentation and induction of labour as independent risk factors for CP. There was a significant increased risk of CP in children born in breech presentation compared to vertex presentation, in particular for singletons born at term by vaginal delivery. Breech presentation was however not associated with specific subtypes of CP or with the extent of gross or fine motor impairments. There was also an increased risk for CP in children after induction of labour. Induction of labour was associated with a higher proportion of children with the bilateral spastic subtype as well as in those born at term with four-limb involvement. When we studied multiple risk factors (maternal disease, assisted fertilization, plurality, abnormal placental structure, bleeding in pregnancy, small for gestational age, abnormal presentation, Apgar score at 5 minutes

Extreme prematurity carries a high risk of neurosensory disability.Examine which information obtained pre-, peri- and postnatally may be predictive of neurosensory disabilities at 2 years of age.Prospective observational study of all infants born in Norway in 1999 and 2000 with gestational age (GA) 22-27 completed weeks or birth weight (BW) of 500-999 g.Incidence of neurosensory disabilities.Of 373 surviving children, 30 (8%) had major neurosensory disabilities (26 CP, 6 blind, 3 deaf), and a further 46 (12%) had minor visual or hearing disabilities. The rate of major neurosensory disabilities was 19 of 99 (19%) for children with GA 23-25 vs. 8 of 189 (4%) for GA 26-27 weeks (p0.001). In a multivariable model, only morbidities detected in the neonatal intensive care unit (NICU) were associated with major neurosensory disabilities; adjusted odds ratios (95% confidence intervals) were 68.6 (18.7, 252.2) for major abnormalities on cerebral ultrasound, 6.8 (1.7, 27.4) for retinopathy of prematurity (ROP) grade2, 3.2 (1.0, 9.7) for ROP grade 1-2, 6.5 (1.9, 22.3) for prolonged use (or = 21 days) of steroid treatment for lung disease and 3.1 (1.0, 9.4) for clinical chorioamnionitis. The visual outcome was strongly related to the degree of ROP (p0.001), and all who had a normal hearing screen in the NICU had normal hearing at 2 years.NICU morbidities, rather than GA or intrauterine growth are the significant predictors of major neurosensory disabilities among extreme prematurity surviving to discharge from the NICU.

Background. It is unknown whether adverse pregnancy-related outcomes in women with pregestational diabetes are associated with later development of end-stage renal disease (ESRD) or death. Methods. We linked data from the Medical Birth Registry of Norway with data from the Norwegian Renal Registry and the Norwegian Cause of Death Registry. Data from up to three pregnancies for women with a first singleton delivery from 1967 to 1994 were included and analysed in a cohort design using Cox regression. Results. Altogether, 639 018 women were included in the analyses, among whom 2204 women had diabetes mellitus before pregnancy. Their first pregnancy was complicated by pre-eclampsia in 13.2%, low birth weight offspring (

Objective To estimate whether a history of fetal growth restriction, abruptio placentae, preeclampsia, or live preterm birth is associated with excess risk of stillbirth in a subsequent pregnancy. We also estimated the maternal and paternal contributions to such effects. Methods This was a population-based cohort study from 1967 to 2005. Pairs of first and second, second and third, third and fourth, and fourth and fifth births were identified among all births from the Medical Birth Registry of Norway; 747,221 pairs with the same parents, 51,708 with the same mother and different father, and 65,602 with the same father and different mother. The associations of gestational age categories (22-27, 28-32, 33-36, and at or above 37 weeks), small for gestational age (SGA), preeclampsia, and abruptio placenta in the first pregnancy with stillbirth and late abortion in the second were assessed by odds ratios (ORs) obtained by logistic regression. Results The baseline rate of stillbirth during the study period was 1.0% of all births from 16 weeks of gestation. After births with gestational age 22-27, 28-32, and 33-36 weeks of gestation, stillbirth was six, three and two times more likely to occur than after a term birth (OR 5.7, 95% confidence interval [CI] 4.2-7.6; OR 2.6, 95% CI 2.1-3.3; and OR 1.7, 95% CI 1.5-1.9, respectively). Odds ratios of stillbirth subsequent to pregnancies with SGA, preeclampsia, and abruptio placentae were 1.7 (95% CI 1.6-1.9), 1.6 (95% CI 1.5-1.9), and 2.8 (95% CI 2.2-3.5), respectively, and increased with severity of the conditions. Gestational age below 33 weeks with preeclampsia or SGA carried 6-9 and 6-13-fold effects on later stillbirth, respectively. Men who fathered a pregnancy with preterm preeclampsia were significantly more likely to father a stillbirth in another woman (OR 2.4, 95% CI 1.1-5.5). Conclusion Live preterm birth, fetal growth restriction, preeclampsia, and abruptio placenta are strongly associated with later stillbirth. Level of evidence II.

The objective of this study was to analyze whether maternal negative affectivity assessed in pregnancy is related with subsequent infant food choices.The study design was a cohort study.The subjects were mothers (N=37 919) and their infants participating in the Norwegian Mother and Child Cohort Study conducted by the Norwegian Institute of Public Health.Maternal negative affectivity assessed prepartum (Hopkins Symptom Checklist 5 (SCL-5) at weeks 17 and 30 of pregnancy), introduction of solid foods by month 3 and feeding of sweet drinks by month 6 (by the reports of the mothers) were analyzed.Mothers with higher negative affectivity were 64% more likely (95% confidence interval 1.5-1.8) to feed sweet drinks by month 6, and 79% more likely (95% confidence interval 1.6-2.0) to introduce solid foods by month 3. These odds decreased to 41 and 30%, respectively, after adjusting for mother's age, body mass index (BMI) and education.The maternal trait of negative affectivity is an independent predictor of infant feeding practices that may be related with childhood weight gain, overweight and obesity.

Background:It is known that onset of rheumatoid arthritis (RA) is increased post partum.Objective:To compare incidence rates between RA and other chronic arthritides (OCA) 0–24 months after delivery, and to compare the incidence rates within each group 0–24 versus 25–48 months post partum.Methods:Premenopausal women from a Norwegian patient register were linked with the Medical Birth Registry of Norway to study the interval between delivery and time of diagnosis. Cox regression analysis with adjustments for age at delivery and birth order was applied to compare proportions of incident cases of RA and OCA with onset 0–24 months post partum. Poisson regression analysis with adjustment for the population at risk was applied to estimate the incidence rate ratio (IRR) 0–24 versus 25–48 months post partum.Results:Of 183 RA and 110 patients with OCA diagnosed after delivery, 69 (37.7%) had RA and 31 (28.2%) OCA during the first 24 months post partum (p = 0.09). The IRR (95% CI) for diagnosis during 0–24 months versus 25–48 months was 1.73 (1.11 to 2.70) (p = 0.01) for RA, 1.05 (0.59 to 1.84) (p = 0.86) for OCA. The IRR was 2.23 (1.06 to 4.70) and 1.87 (0.67 to 5.21), respectively, when only considering diagnoses after the first pregnancy. Clinical characteristics were similar within each diagnostic group.Conclusion:The proportions of incident cases with onset 0–24 months after delivery were not different between RA and OCA. A peak in incidence during 0–24 months was seen in the RA group, both when considering all pregnancies and only the first pregnancy.

Biotopes with intact sphagnum vegetation were studied in Naustdal, West Norway: the health district with the former highest leprosy incidence rates in Norway. Concentration of acid-fast bacilli and concentration of non-cultivable acid-fast bacilli found in the vegetation fluid were compared with a series of variables related to the local environment and to the samples of vegetation. In bivariate analyses high concentrations were found in biotopes with orientation toward South, with a high coverage of vascular plants and with presence of Ericaceae. High concentrations were also found where dry weight of a vegetation was high, where pH in the fluid was low and where dry weight of the fluid was high. In a multivariate analysis, log-linear model, based on concentration of acid-fast bacilli as the dependent variable and orientation, pH, dry weight of vegetation and dry weight of fluid as the independent variables, all two-factor effects including the dependent variable were retained in the model. Furthermore, orientation versus dry weight of vegetation and dry weight of fluid versus dry weight of vegetation were retained.

Cerebral palsy (CP) is still the most common cause of chronic motor disability in hildhood. Until now, there has not been any previous national study of the anorama of subtypes, severity or risk factors among children with CP in Norway. his is a population based study of a cohort of children with CP born 1996 to 1998 in orway. These children are recorded in the Cerebral Palsy Register of Norway. The P definition and classification system agreed on by the Surveillance of Cerebral alsy in Europe (SCPE) are applied. The study showed that the prevalence of CP in orway was 2.1 per 1000 live births, comparable with other similar populations. Most children were classified in the spastic bilateral subtype (49%), about ne third (33%) in the spastic unilateral subtype and less than 10% in the dyskinetic r in the ataxic subtype. Both the distribution of subtypes and gross motor function impairments were comparable with other populations in developed countries. More children in our study had fine motor function impairments, as well as associated impairments. The associated impairments included both impairment of speech and feeding, in addition to impairments of vision, hearing, cognition and presence of active epilepsy. We identified both breech presentation and induction of labour as independent risk factors for CP. There was a significant increased risk of CP in children born in breech presentation compared to vertex presentation, in particular for singletons born at term by vaginal delivery. Breech presentation was however not associated with specific subtypes of CP or with the extent of gross or fine motor impairments. There was also an increased risk for CP in children after induction of labour. Induction of labour was associated with a higher proportion of children with the bilateral spastic subtype as well as in those born at term with four-limb involvement. When we studied multiple risk factors (maternal disease, assisted fertilization, plurality, abnormal placental structure, bleeding in pregnancy, small for gestational age, abnormal presentation, Apgar score at 5 minutes

We assessed whether fetal growth restriction without pregnancy-induced hypertension (PIH) is associated with the different clinical subgroups of PIH in the subsequent pregnancy. We also assessed the maternal and paternal contributions to this effect. Pairs of first and second, second and third, third and fourth, and fourth and fifth births were identified among all of the births in Norway: 137 375 pairs with same mother and father, 18 376 pairs with same mother and different fathers, and 18 916 pairs with same father and different mothers. Second births in each pair were restricted to those that occurred in 1998–2005. Odds ratios to predict early onset, severe, and mild preeclampsia and transient hypertension in the second birth from birth weight

Case-control studies have shown an association between low birth weight and risk for renal failure. The Medical Birth Registry of Norway, which comprises data on all births in Norway since 1967, and the Norwegian Renal Registry, which comprises data on all patients who have developed ESRD in Norway since 1980, were used to examine whether birth-related variables were associated with risk for ESRD. Of the 2,183,317 children born between 1967 and 2004, 526 were found in the ESRD registry. Compared with birth weight in the 10th to 90th percentiles, births

OBJECTIVE To explore the association between mode of delivery and subsequent fertility. METHODS Deliveries registered in the Medical Birth Registry of Norway were linked to mothers through national identification numbers. The study population was 596,341 women who had their first delivery during 1967-1996, and who were followed up through 2003. We compared rates of continuation to a subsequent birth according to mode of previous delivery (cesarean compared with vaginal). RESULTS If the first child survived the first year of life, cesarean delivery was associated with a significantly reduced probability of a second birth (relative risk [RR] 0.82, 95% confidence interval [CI] 0.81-0.83 during 1967-1981, and RR 0.88, 95% CI 0.88-0.89 during 1982-1996). Following a stillbirth or an infant loss, the association was less strong during 1967-1981 (RR 0.93, 95% CI 0.89-0.97) and no longer significant during 1982-1996 (RR 1.00, 95% CI 0.97-1.03). A similar pattern was observed from the second to the third birth and in subgroup analyses of women with preeclampsia or breech presentation and in an obstetric low-risk group. CONCLUSION Cesarean delivery was more strongly associated with reduced fertility if the infant survived than if it was stillborn or died. This suggests that the reduced fertility was to a large degree voluntary and not related to the indication, nor to any physical consequence, of the cesarean delivery. LEVEL OF EVIDENCE II.

Most studies on disability pension (DP) have focused on work conditions, socio-economic status and other contemporary factors. We wanted to study possible determinants of an early DP with a life course perspective within a large register-based cohort, with a main focus on the biological and social factors from childhood. We established a longitudinal, population-based cohort of all persons liveborn in Norway between 1967 and 1976. Through linkage between several national registers we obtained personal data on biological/health related as well as social background factors. After excluding persons who died, emigrated or were granted a DP before age 20 years (at which age follow-up started) and persons who did not become gainfully employed during the study period, the study population consisted of 595,393 persons. They were categorized into four strata according to gender and educational attainment. Adjusted hazard ratios (HR) for granting a DP until the end of 2003 and the corresponding population attributable risks (PAR) were computed. A total of 9,649 persons (1.6%) were granted a DP during follow-up. The disability risk was slightly higher among women than among men (1.7% vs. 1,5%). The following PARs were found: birth weight below the mean 5.7%, chronic childhood disease 6.8%, maternal marital status 4.4% and parental disability 8.8%. Low educational achievement was highly associated with DP, with a PAR more than twice as high as the overall PAR for the childhood factors. Early DP is associated with several biological and social background factors from childhood. It also shows a strong dependency on educational achievement.

Objective To produce population-based, gender- and gestational-age-specific centile curves for placental weight. Design Population study. Setting Medical Birth Registry of Norway. Population All singleton live births in Norway from 1 January 1999 to 31 December 2002. Methods In a cohort of children born in Norway, placental weights and the ratio of the birthweight to the placental weight were analysed to produce percentile curves. Main outcome measures Placental weight, birthweight-to-placental weight ratio. Results Tables and figures are presented for placental percentiles curves according to gestational age and gender. Also, tables and figures are presented for the ratio of birthweight to placental weight. CONCLUSIONS To our knowledge, this is the first time that population percentile curves have been produced for placental weights and hence for the ratio of birthweight to placental weight. These percentile curves may act as a reference for other populations as well until population-specific curves can be produced.

We assessed whether a pregnant woman who was born small for gestational age has increased risk of pregnancy-induced hypertension (PIH), and whether the same applies to a pregnant partner of a man who was born small for gestational age. We linked generational data from the medical birth registry of Norway (1967–2005). Female and male newborns were identified as parents with 197 716 and 131 959 first or second pregnancies from 1998 to 2005, respectively. In the first pregnancy in women who were born with birth weight

Familial correlations in birth weight and gestational age have been explained by fetal and maternal genetic factors, mainly in studies on offspring of twins. The aim of the present intergenerational study was to estimate and compare fetal and maternal genetic effects and shared sibling environmental effects on birth weight and gestational age and also on crown-heel length and head circumference. The authors used path analysis and maximum likelihood principles to estimate these effects and, at the same time, to adjust for covariates. Parent-offspring data were obtained from the Medical Birth Registry of Norway from 1967 to 2004. For the analysis of birth weight and crown-heel length, 101,748 families were included; for gestational age, 91,617 families; and for head circumference, 77,044 families. Assuming no cultural transmission and random mating, the authors found that fetal genetic factors explained 31% of the normal variation in birth weight and birth length, 27% of the variation in head circumference, and 11% of the variation in gestational age. Maternal genetic factors explained 22% of the variation in birth weight, 19% of the variation in birth length and head circumference, and 14% of the variation in gestational age. Relative to the proportion of explained variation, fetal genes were most important for birth length and head circumference.

In order to investigate the extent to which musculoskeletal sickness absence was influenced by a range of circumstances concerning family background and health in early life, we established a register-based cohort of all live-born in Norway between 1967 and 1976. Personal data on parental factors and health early in life were recorded prospectively from birth onward in the Medical Birth Registry of Norway, the National Insurance Administration, Statistics Norway, and the Central Population Register. We collected data in the National Insurance Administration on the first spell of medically certified long-term (>16 days) musculoskeletal (International Classification of Primary Care group L) sickness absence in 2000-2003 among 378, 356 participants who were considered to be at risk of sickness absence on January 1st, 2000. The 4-year musculoskeletal absence risk was 0.264 for women and 0.156 for men. Parental education level was associated with musculoskeletal sickness absence, with increasing adjusted relative risks by decreasing educational level for both genders. Associations with other early determinants (birth weight, childhood disease, parental survival, parental disability, parental income, and parental marital status) were all close to unity. Parental education level attributed 36% (95% confidence interval 33-38) to the population risk for women and 67% (64-70) for men. The parental education association was partly mediated through own educational attainment, which was strongly associated with musculoskeletal sickness absence in itself. Our data suggest that mechanisms acting early in life could influence later risk of musculoskeletal sickness absence.

AIM: To assess parental risk behaviour before and after a sudden infant death syndrome (SIDS) information campaign with special emphasis on associations with maternal age, education, marital status and birth order. METHODS: Data from questionnaires sent to all mothers who gave birth in Norway during a period before the campaign were compared with corresponding data obtained after the campaign. RESULTS: Prevalence of non-supine sleeping position decreased from 33.7% to 13.6% while changes in smoking, non-breastfeeding and co-sleeping were disappointing. Risk factors were particularly prevalent in young mothers, but also in mothers with a minimum period of education, non-cohabitation and at birth order 2+. CONCLUSIONS: Non-supine sleeping decreased to a level that has never been reported before. In future campaigns, subgroup-specific measures may be needed. Language: en

Aim: To study circadian variation in the sudden infant death syndrome (SIDS) and possible associations with risk factors for SIDS. Methods: A questionnaire-based case-control study matched for place of birth, age and gender was conducted in Denmark, Norway and Sweden: The Nordic Epidemiological SIDS Study. The study comprised 244 SIDS victims and 869 control infants between September 1992 and August 1995. The main outcome was hour found dead. Results: A significant circadian pattern was observed among the 242 SIDS victims with a known hour found dead, with a peak at 08.00-08.59 in the morning (n= 33). Of the SIDS victims, 12% were found dead at 00.00-05.59, 58% at 06.00-11.59, 21% at 12.00-17.59 and 9.0% at 18.00-23.59. When comparing night/morning SIDS and day/evening SIDS (found dead 00.00-11.59 and 12.00-23.59, respectively), the proportion of night/morning SIDS was high among infants of smoking mothers (81% vs 53%, p < 0.001), infants with a reported cold (82% vs 64%, p= 0.007) and infants sleeping side/supine (81% vs 60%, p < 0.001). No associations were observed between hour found dead and other sociodemographic risk factors for SIDS. Risk (odds ratio and 95% confidence interval) of night/morning SIDS and day/evening SIDS was 7.0 (4.5-10.9) and 1.5 (0.8-2.5), respectively, for maternal smoking, 2.2 (1.5-3.1) and 0.6 (0.3-1.3), respectively, if the infant had a reported cold, 3.7 (2.1-6.6) and 3.1 (1.1-8.4), respectively, if the infant was put to sleep in the side position (supine reference), and 11.0 (5.9-20.2) and 21.6 (7.6-60.8), respectively, if the infant was put to sleep in the prone position. Conclusion: The observed higher proportion of night/morning cases in SIDS if the mother smoked, if the infant was reported to have a cold and if the infant was sleeping side/supine may contribute to the understanding of some epidemiological characteristics of SIDS.

To explore the association between smoking and breastfeeding, we obtained data from a retrospective questionnaire-based national survey comprising a random sample (n = 34 799) of all mothers giving birth in Norway 1970-91. Variables studied were postpartum smoking habits for both parents, duration of breastfeeding, infant's year of birth and parental age. The response rate was 70% (n = 24 438). During the study period, the maternal postpartum smoking prevalence decreased from 38% to 26%. The proportion breastfeeding at 6 months increased from 15% to 44% among smokers, and from 30% to 72% among non-smokers. In spite of a considerable increase in breastfeeding both among smokers and non-smokers, the proportion of breastfeeding, non-smoking women at 6 months was twice that of smoking women during the whole period. Furthermore, the duration of breastfeeding was shorter among young mothers and when the fathers were smoking. There was epidemiological evidence that the effect on breastfeeding of smoking might represent both biological and social mechanisms.

The aim of this study was to investigate associations between sudden infant death syndrome (SIDS) and social factors in the Nordic countries. A case-control study was conducted in Denmark, Norway and Sweden: The Nordic Epidemiological SIDS Study. Parents of 244 SIDS infants and 869 control infants matched on gender, age at death and place of birth filled in questionnaires. The dataset was analysed by conditional logistic regression. In univariate analysis, the following sociodemographic factors were associated with an increased risk of SIDS: low maternal age [odds ratio (OR) 7.8; 2.8-21.5], high birth order (OR 4.4; 2.5-7.5), single motherhood (OR 2.9; 1.7-5.0), low maternal education (OR 4.5; 2.8-7.1), low paternal education (OR 3.0; 1.9-4.7), maternal unemployment (OR 2.4; 1.8-3.4) and paternal unemployment (OR 4.0; 2.7-5.9). In a multivariate analysis where maternal smoking was also included, only paternal unemployment, young maternal age and high birth order remained significantly associated with SIDS. Housing conditions were not associated with SIDS. However, the risk of SIDS was high if the family had lived in their present home for only a few years (OR 2.3; 1.3–4.1). Sociodemographic differences remain a major concern in SIDS in a low-incidence situation and even in an affluent population with adequate health services.

The Medical Birth Registry of Norway (MBRN) has registered all births in Norway since 1967 and diabetes is registered as a maternal diagnosis. We present original data assessing the validity of the diabetes diagnosis. Among women with known pre-gestational type 1 diabetes, 97% of births during 1976-1998 (old registration form) were identified as pre-gestational diabetes in the MBRN. For births 1999-2004 (new registration form), 94% were identified as pre-gestational diabetes in the MBRN. Of cases coded as pre-gestational diabetes by the MBRN, 80% were confirmed by the medical record for births during 1998, while more than half of the births incorrectly coded as pre-gestational diabetes really were gestational diabetes. Among births coded as gestational diabetes, 89% were confirmed in the medical record. In conclusion, the sensitivity of the pregestational diabetes diagnosis in the Medical Birth Registry of Norway was very good, particularly in the earlier period, but the information in the MBRN on births before 1999 was not sufficient to classify pregestational diabetes as type 1 – or type 2 diabetes. The type of diabetes can be specified for births from 1999 onwards, but the predictive values are unknown. The predictive value for pre-gestational diabetes in 1998 was less than optimal but acceptable for a routine registry not specialised for diabetesGravide kvinner med type 1 diabetes har økt risiko for komplikasjoner i svangerskapet, medfødte misdannelser og dødfødsel. Data fra medisinsk fødselsregister (MFR) har vært grunnlag for viktige publikasjoner om risiko for komplikasjoner hos gravide kvinner med diabetes. I tillegg til å gi en kort oversikt over disse publikasjonene presenterer vi data om validiteten til diabetesdiagnosen. Av fødsler til og med 1998 med kjent type 1 diabetes før svangerskapet basert på opplysninger fra Norsk diabetesregister (NDR) ble 97% registrert som diabetes før svangerskapet i MFR (gammelt registreringsskjema). For fødsler 1999-2004, ble 94% kodet som pre-gestasjonell (type 1- eller type 2-) diabetes. Ved sammenligning med sykehusjournalen til kvinner identifisert i MFR med diabetesdiagnose før svangerskapet (fødsler i 1998) ble diabetes før svangerskapet i følge MFR bekreftet i journalen i 80% av tilfellene. Av fødsler kodet med svangerskapsdiabetes ble 89% bekreftet i journalen. Vi konkluderer med at sensitiviteten for pre-gestasjonell diabetes er meget god, spesielt for fødsler før 1999, men MFR kan for denne perioden ikke brukes til å klassifisere pre-gestasjonell diabetes hos mor som type 1- eller type 2 diabetes. For fødsler fra og med 1999 kan type diabetes spesifiseres, men prediktiv verdi for disse diagnosene er ikke undersøkt. Prediktiv verdi for diagnosen pre-gestasjonell diabetes i MFR for fødsler i 1998 er ikke optimal, men akseptabel for et rutineregister som ikke har diabetes som hovedfokus.

Worldwide rising cesarean section rates over the past decades have caused much concern. Studies on the association between cesarean section and maternal social background have reported conflicting results.A cohort study, comprising 837,312 birth order one deliveries notified to the population-based Medical Birth Registry of Norway during 1967-2004. The relative risk of cesarean section (from 1988 onwards planned and emergency cesarean section) according to maternal educational level was assessed in all deliveries, in an obstetric low-risk group and within groups of medical/obstetric high-risk conditions.Throughout the study period, the lowest educated had the highest risk of cesarean section, followed by the medium educational group. In all deliveries, the adjusted relative risk of cesarean section for the lowest versus the highest educated increased from 1.16 (95% CI 1.09-1.23) in the 1967-76 period to 1.34 (95% CI 1.27-1.42) in the 1996-2004 period, and in the obstetric low risk group from 1.19 (95% CI 1.10-1.30) to 1.50 (95% CI 1.38-1.63). From 1988 onwards, the lowest educated had the highest risk of both planned and emergency cesarean section, followed by the medium educational group.The lowest educated had the highest risk of cesarean section, followed by the medium educational group, and the differences gradually increased during 1967-2004. This trend could be accounted for by increasing vulnerability of the lowest educational group due to a strong social migration, and by increased occurrence of cesarean section on maternal request among the lowest educated in recent years.