Background Previous studies have shown a relationship between maternal stress during pregnancy and increased risk of malformations in children, eg: cleft lip, palate, neural tube and heart defects. To our knowledge no previous studies has had a job-related angle to maternal stress during pregnancy. The present project therefore examines if maternal exposure to psychosocial job strain (high demands and low control) measured by questionnaire early in pregnancy is associated with congenital malformations (all), cardiovascular malformations and malformations in the musculoskeletal system.
Methods We use the Danish National Birth Cohort with more than 100.000 children at baseline. In the present study 60,120 pregnancies are included due to inclusion criteria as: working, pregnant when interviewed, singleton pregnancy and information on exposure, covariates and outcome. Congenital malformations are available from the Danish Medical Birth Register with ICD-10 codes. Analyses are controlled for maternal age, BMI, parity, smoking, alcohol use, type of work, maternal serious disease and gestational age at interview.
Results In total 3,069 cases of malformations were registered in the study population, 582 of these were cases of circulatory malformations and 1,555 of musculoskeletal malformations. Logistic regression analyses showed that high strain was not associated with increased risk of any type of malformations (OR = 0.99, CI: 0.85–1.15), circulatory (OR = 1.04, CI: (0.75–1.44) or musculoskeletal malformations (OR = 0.88, CI: 0.70–1.10). The analyses were adjusted for maternal age, parity, smoking, alcohol, maternal BMI, type of work, maternal serious disease, gestational age at interview. Crude analyses did not change the results significantly.
Conclusion The results support the null-hypothesis; that the risk of having a child with congenital malformations is independent of psychosocial job strain in this sample from the Danish National Birth Cohort. As this contradicts previous findings (e.g. bereavement studies, with loss of a child or husband), a discussion regarding exposure and sample size could be beneficial.