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Background: Several studies have linked coffee intake and smoking to foetal death, but a possible interaction between both exposures remains unknown., Methods: We studied, within the Danish National Birth Cohort, the potential interaction between smoking and coffee drinking while pregnant on the risk of foetal (early and late) death. The study included 90 086 pregnant women, with information about their smoking habit and coffee intake in early pregnancy, and several potential confounding factors. Interaction was studied by calculating both the hazard ratio (HR) in Cox's regression (linear and smoothed restricted cubic spline) and the interaction contrast ratio (ICR)., Results: Women who neither smoked nor drank coffee were used as the reference group. Drinking more than 3 cups/d of coffee was associated with the highest risk of foetal death, spontaneous abortion and stillbirth for all smoking status (non-smoker, ≤10 or > 10 cigarettes/d). Among smokers, the combination with drinking <3 cups/d of coffee presented the lowest HRa for foetal death, spontaneous abortion and stillbirth. The ICRs were negative when considering smokers who had a coffee intake up to 3 cups/d, but they were positive for those who had a higher coffee intake, suggesting the effect of coffee intake may be non-linear., Conclusion: Our results suggest that the combined effect of smoking and coffee intake during pregnancy on the risk of foetal death is coffee-dose-dependent. A low coffee intake may reduce the risk of foetal death associated with smoking while a high coffee intake increases the risk.

Aims: To explore the relation between employment status, type of unemployment and pregnancy outcomes., Methods: A cohort study of 7,282 pregnancies of unemployed women and 56,014 pregnancies among women in paid jobs was performed within the Danish National Birth Cohort. Pregnancy outcomes were ascertained and information about lifestyle, occupational, medical, and obstetric factors was obtained. Logistic regression was used to calculate odds ratios (OR) for fetal loss, congenital anomalies, multiple births, sex ratio, preterm and very preterm birth and small for gestational age status, adjusting for lifestyle, medical and obstetric factors., Results: There were no differences in pregnancy outcomes between employed and unemployed women but women receiving unemployment benefit had an increased risk of preterm birth (adjusted OR (aOR) 1.16, 95% confidence interval (95% CI) 1.03-1.31) and having a small for gestational age child (aOR 1.08, 95% CI 1.00-1.19) compared with employed women. Women receiving sickness or maternity benefit had an increased risk of multiple birth (aOR 1.70, 95% CI 1.43-2.04), preterm (aOR 1.47, 95% CI 1.22-1.77) and very preterm birth (aOR 1.88, 95% CI 1.22-2.89), while those receiving an unreported type of support had an increased risk of preterm birth (aOR 1.40, 95% CI 1.02-1.93)., Conclusions: We found no indication that being unemployed during pregnancy benefits or endangers the health of the child. Within the subgroups of unemployed women, we observed that women receiving unemployment and sickness or maternity benefits were at higher risk for some adverse pregnancy outcomes.

Background: Sex hormones closely regulate development of the male genital organs during fetal life. The hypothesis that xenobiotics may disrupt endogenous hormonal signalling has received considerable scientific attention, but human evidence is scarce., Objectives: We analyse occurrence of hypospadias and cryptorchidism according to maternal and paternal occupational exposure to possible endocrine disrupting chemicals., Methods: We conducted a follow-up study of 45,341 male singleton deliveries in the Danish National Birth Cohort during 1997-2009. Information on work during pregnancy was obtained by telephone interviews around gestational week 16. Parents' job titles were classified according to DISCO-88. A job exposure matrix for endocrine disrupting chemicals (EDCs) was implemented to assess occupational exposures. The Medical Birth and National Hospital Register provided data on congenital anomalies diagnosed at birth or during follow-up, which ended in 2009. Crude and adjusted hazard ratios (HR) were obtained from Cox regression models., Results: Among all pregnancies, 6.3% were classified as possibly or probably exposed to EDCs. The most prevalent occupations conferring possible exposure were cleaners, laboratory technicians, hairdressers and agricultural workers (58% of all potentially exposed). The final cumulative incidence of cryptorchidism in boys was 2.2% (1002 cases), and of hypospadias 0.6% (262 cases). The occurrence of hypospadias increased when mothers were probably [HRa = 1.8 (95% CI 1.0-2.6)] or possibly exposed to one or more EDCs [HRa = 2.6 (95% CI 1.8-3.4). Possible paternal exposure to heavy metals increased the risk of hypospadias [HRa 2.2 (95% CI: 1.0-3.4)] and cryptorchidism [HRa 1.9 (95% CI: 1.1-2.7)]. None of the exposure groups reached statistical significance., Conclusion: The study provides some but limited evidence that occupational exposure to possible endocrine disrupting chemicals during pregnancy increases the risk of hypospadias.

In hospitals, women of reproductive age do a range of work tasks, some of which are known to carry potential risks. Tasks such as working with radiation, chemicals, and infectious agents, as well as performing heavy lifting or tasks requiring erratic sleep patterns have been reported to increase the risk of reproductive failures. Our aim was to study pregnancy outcomes in female hospital workers in Denmark. We performed a cohort study of 5976 female hospital workers and used as a reference group 60,890 women employed outside of hospitals. The reproductive health of hospital workers working during pregnancy is comparable to those of non-hospital workers for the majority of reproductive failures studied. However, an increased prevalence of congenital abnormalities was noted in some subgroups of hospital workers, which may indicate that some hospital work still entails fetotoxic hazards.

Twinning rates have changed substantially over time for reasons that are only partly known. In this study we studied smoking, coffee and alcohol intake, and their possible interaction with obesity as potential determinants of twinning rates using data from the Danish National Birth Cohort between 1996 and 2002. We identified 82,985 pregnancies: 81,954 singleton and 1031 twins. For the twins we had data to classify 121 as monozygotic, 189 dizygotic (same sex), 313 dizygotic (opposite sex) but, 408 were of the same sex but with unknown zygosity. All mothers were interviewed about their prepregnancy weight and height, coffee and alcohol intake, smoking habits, and potential confounding factors at early stages of pregnancy. We identified smoking (> 10 cigarettes/day) as a possible determinant of twinning, particularly for dizygotic twinning rates (same sex) and furthermore corroborated that obesity and the mother's age are strong correlates of twinning. Others have found coffee intake to increase twinning rates but that is not seen in these data.

Objective: We examined whether maternal smoking and use of nicotine substitutes during the first 12 weeks of pregnancy increased the prevalence of congenital malformations in general and of certain congenital malformations in particular., Methods: In the Danish National Birth Cohort (1997-2003) we identified 76,768 pregnancies (and their subsequent singleton births); 20,603 were exposed to tobacco smoking during the first 12 weeks of pregnancy. Birth outcomes were collected by linkage to the Central Population Register, the National Patients Register, and the National Birth Register. We identified congenital malformations from the Hospital Medical Birth Registry as they were recorded at birth or in the first year of follow-up., Results: Smoking mothers were younger, weighed less, consumed more alcohol, and had received less education. Children exposed to prenatal tobacco smoking had no increase in congenital malformations prevalence compared with the nonexposed children in both crude and adjusted analyses. Children born to nonsmokers, but who used nicotine substitutes, had a slightly increased relative congenital malformations prevalence ratio; relative prevalence rate ratio was 1.61 (95% confidence interval 1.01-2.58), which represents a 60% increased risk. When the analysis was restricted to musculoskeletal malformations, the relative prevalence rate ratio was 2.63 (95% confidence interval 1.53-4.52)., Conclusion: Our results showed no increase in congenital malformations related to prenatal tobacco smoking. However, we identified an increase of malformations risk in nonsmokers using nicotine substitutes. This finding needs to be replicated in other data sources., Level of Evidence: II-2.