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This is an update of the Norwegian Mother and Child Cohort Study (MoBa) cohort profile which was published in 2006. Pregnant women attending a routine ultrasound examination were initially invited. The first child was born in October 1999 and the last in July 2009. The participation rate was 41%. The cohort includes more than 114 000 children, 95 000 mothers and 75 000 fathers. About 1900 pairs of twins have been born. There are approximately 16 400 women who participate with more than one pregnancy. Blood samples were obtained from both parents during pregnancy and from mothers and children (umbilical cord) after birth. Samples of DNA, RNA, whole blood, plasma and urine are stored in a biobank. During pregnancy, the mother responded to three questionnaires and the father to one. After birth, questionnaires were sent out when the child was 6 months, 18 months and 3 years old. Several sub-projects have selected participants for in-depth clinical assessment and exposure measures. The purpose of this update is to explain and describe new additions to the data collection, including questionnaires at 5, 7, 8 and 13 years as well as linkages to health registries, and to point to some findings and new areas of research. Further information can be found at [www.fhi.no/moba-en]. Researchers interested in collaboration and access to the data can complete an electronic application available on the MoBa website above.

Summary Tvinnereim HM, Lygre GB, Haug K, Schreuder P, Klock K. A biobank of primary teeth within the Norwegian Mother and Child Cohort Study (MoBa): a resource for the future. Paediatric and Perinatal Epidemiology 2012; 26: 264–271. The Norwegian Mother and Child Cohort Study (MoBa) is a prospective population-based cohort study including >100 000 pregnancies and following the children through childhood, using questionnaires and collecting biological samples. The aim of MoBa is to test specific aetiological hypotheses by estimating the association between exposure and disease, aiming at prevention. A biobank for exfoliated primary teeth collected from the children participating in MoBa has been established (MoBaTooth Biobank). Samples of tooth tissues from the primary dentition can give information about exposure to toxic and essential elements during fetal life and early infancy. Prenatally and postnatally formed tooth tissues permanently document early exposures unlike other biomarkers, as teeth form incrementally at a known rate. Results from tooth analyses will be coupled with corresponding information in the multiple questionnaires and data from analysis of other biological samples collected by MoBa. Invitations to donate one or more teeth are sent to all mothers/children in the period 2008–2016, when the child is 6.75 years old. By August 2011, 7400 participants had been recorded into the MoBaTooth database donating altogether 9798 teeth (1.3 teeth per child). The response rate was 24%, but there is a lag of >1 year in the response. Data from the tooth biobank can supply MoBa with important additional information on the uptake of trace elements during fetal life and early infancy. This information can illuminate possible causal factors of health and disease in the future.

The reported prevalence of autism spectrum disorders (ASDs) has increased by 5- to 10-fold over the past 20 years. Whether ASDs are truly more frequent is controversial; nonetheless, the burden is profound in human and economic terms. Although autism is among the most heritable of mental disorders, its pathogenesis remains obscure. Environmental factors are proposed; however, none is implicated. Furthermore, there are no biomarkers to screen for ASD or risk of ASD. The Autism Birth Cohort (ABC) was initiated to analyze gene x environment x timing interactions and enable early diagnosis. It uses a large, unselected birth cohort in which cases are prospectively ascertained through population screening. Samples collected serially through pregnancy and childhood include parental blood, maternal urine, cord blood, milk teeth and rectal swabs. More than 107,000 children are continuously screened through questionnaires, referral, and a national registry. Cases are compared with a control group from the same cohort in a 'nested case-control' design. Early screening and diagnostic assessments and re-assessments are designed to provide a rich view of longitudinal trajectory. Genetic, proteomic, immunologic, metagenomic and microbiological tools will be used to exploit unique biological samples. The ABC is a paradigm for analyzing the role of genetic and environmental factors in complex disorders.

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 Norwegian Mother and Child Cohort Study (MoBa) is a prospective population-based cohort study including more than 100,000 pregnancies and following the children through childhood, using questionnaires and collecting biological samples. The aim of MoBa is to test specific aetiological hypotheses by estimating the association between exposure and disease, aiming at prevention. A biobank for exfoliated primary teeth collected from the children participating in MoBa has been established (MoBaTooth Biobank). Samples of tooth tissues from the primary dentition can give information about exposure to toxic and essential elements through foetal life and early infancy. Prenatally and postnatally formed tooth tissues permanently document early exposures unlike other biomarkers, as teeth form incrementally at a known rate. Results from tooth analyses will be coupled to corresponding information in the multiple questionnaires and data from analysis of other biological samples collected by MoBa. Invitations to donate one or more teeth are sent to all mothers/children in the period 2008-2016, when the child is 6¾ years old. By November 2014 21,748 participants had been recorded into the MoBaTooth database donating altogether 28,272 teeth (1.3 teeth per child). The response rate was 24%, but there is a lag of more than one year in the response. Data from the tooth biobank can supply MoBa with important additional information on the uptake of trace elements during foetal life and early infancy. This information can illuminate causal factors of health and disease in the future. publishedVersion

Background: Autism spectrum disorders (ASDs) are characterized by persistent deficits in social communication and interaction and restricted, repetitive patterns of behavior, interests or activities. In most cases, the cause of ASD is likely to be a combination of genetic predisposition and environmental exposures occurring in fetal life or early infancy. Consequently, a prospective pregnancy cohort like MoBa represents an ideal platform for studies of ASDs in children.Methods: The Autism Birth Cohort (ABC) Study has identified potential ASD cases in MoBa through questionnaire- based screening, parental and professional referrals, and linkages to the Norwegian Patient Register. ASD diagnoses have been ascertained through in-person clinical assessments and medical record reviews.Current results: By the end of 2012, the ABC Study had identified 518 ASD cases in MoBa. The ASD prevalence in school-age children is 0.7-0.8%, which is in line with nationwide estimates for Norway. The most important source of ASD case identification was registry linkages, while only a minority was detected through early screening. Published findings show that screening at 18 months misses the majority of ASD cases. Analyses of risk factors for ASDs have shown that maternal use of folic acid supplements in early pregnancy may lower the child’s risk of developing ASDs and that paternal obesity appears to increase the child’s risk of ASDs.Future plans: ASD case identification will continue through annual registry linkages and subsequent reviews of medical records. Analyses of plasma samples and RNA samples will be conducted to investigate prenatal and perinatal microbial exposures, innate immune and inflammatory responses, biomarkers of autism risk, and exposures to xenobiotics. Analyses of deciduous teeth will also investigate the effect of medications and environmental toxins. Exome sequencing of DNA from ASD cases and their parents is ongoing, and will elucidate the role of de novo DNA mutations in the pathogenesis of ASDs. Future epidemiological analyses will explore the results of the 36-month screening for ASDs, the diagnostic stability and developmental trajectories in ASD children, and psychiatric and medical comorbidities in ASDs.

OBJECTIVE--To investigate, in a population based national study, the association between sleeping position of infants and the occurrence of sudden infant death syndrome (SIDS). DESIGN--A retrospective survey and registry based ecological study. A questionnaire based surveillance of sleeping position was obtained in a random sample (n = 34,799) and surveillance of SIDS was based on all infants born in Norway 1967-91, surviving the perinatal period. Variables studied from the questionnaire were usual sleeping position (placed), breast feeding at 3 months, and maternal smoking in pregnancy, and from the Medical Birth Registry maternal age, birth order, and birth weight. RESULTS--Proportion of infants sleeping prone increased from 1970 (7.4%) to 1989 (49.1%) and dropped in 1990 (26.8%) and 1991 (28.3%). Occurrence of SIDS increased from 1970 (1.1/1000) to 1989 (2.0) before dropping in 1990 and 1991 (1.1). IMPLICATION AND RELEVANCE OF RESULTS--A cause effect relationship between prone sleeping and SIDS as suggested in previous studies is supported by the present; and so far only, national study of infants' sleeping position.

The Norwegian Mother and Child Cohort Study (MoBa) is a prospective population-based cohort study including100 000 pregnancies and following the children through childhood, using questionnaires and collecting biological samples. The aim of MoBa is to test specific aetiological hypotheses by estimating the association between exposure and disease, aiming at prevention. A biobank for exfoliated primary teeth collected from the children participating in MoBa has been established (MoBaTooth Biobank). Samples of tooth tissues from the primary dentition can give information about exposure to toxic and essential elements during fetal life and early infancy. Prenatally and postnatally formed tooth tissues permanently document early exposures unlike other biomarkers, as teeth form incrementally at a known rate. Results from tooth analyses will be coupled with corresponding information in the multiple questionnaires and data from analysis of other biological samples collected by MoBa. Invitations to donate one or more teeth are sent to all mothers/children in the period 2008-2016, when the child is 6.75 years old. By August 2011, 7400 participants had been recorded into the MoBaTooth database donating altogether 9798 teeth (1.3 teeth per child). The response rate was 24%, but there is a lag of1 year in the response. Data from the tooth biobank can supply MoBa with important additional information on the uptake of trace elements during fetal life and early infancy. This information can illuminate possible causal factors of health and disease in the future.

Self-selection in epidemiological studies may introduce selection bias and influence the validity of study results. To evaluate potential bias due to self-selection in a large prospective pregnancy cohort in Norway, the authors studied differences in prevalence estimates and association measures between study participants and all women giving birth in Norway. Women who agreed to participate in the Norwegian Mother and Child Cohort Study (43.5% of invited; n = 73 579) were compared with all women giving birth in Norway (n = 398 849) using data from the population-based Medical Birth Registry of Norway in 2000-2006. Bias in the prevalence of 23 exposure and outcome variables was measured as the ratio of relative frequencies, whereas bias in exposure-outcome associations of eight relationships was measured as the ratio of odds ratios. Statistically significant relative differences in prevalence estimates between the cohort participants and the total population were found for all variables, except for maternal epilepsy, chronic hypertension and pre-eclampsia. There was a strong under-representation of the youngest women (

To study the effect on birthweight of maternal smoking, and its modification by study period, maternal age and paternal smoking.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 parental smoking during pregnancy, birthweight, maternal age and infant's year of birth.The overall difference in mean birthweight between non-smoking and smoking mothers was 197 g. The difference in birthweight between non-smoking and smoking mothers increased with maternal age from 182 g (20 years of age) to 232 g (35+ years of age). There was no significant effect of paternal smoking on birthweight when the mother was a non-smoker. When the mother was a smoker and the father was a non-smoker, the birthweight, adjusted for maternal age, was reduced by 153 g (p0.005). However, when both parents smoked, the birthweight, adjusted for maternal age, was reduced by 201 g (p0.0005). Even though the prevalence of paternal smoking decreased by 38% during the study period, there was no significant increase in overall mean birthweight. IMPLICATION AND RELEVANCE OF RESULTS: The negative effect of maternal smoking on birthweight appears to increase with maternal age. For a non-smoking pregnant woman to live with a smoking partner has little, if any, effect on birthweight. The negative effect of paternal smoking was only observed when the mother was smoking and might reflect two possible mechanisms: (1) that a smoking mother has a greater cigarette consumption when the partner also smokes, and (2) that a smoking mother is less concerned about passive smoking than a non-smoking mother.