PRENATAL MATERNAL BEREAVEMENT AND ADULT REPRODUCTIVE IMPAIRMENTS: A POPULATION-BASED COHORT STUDY

INTRODUCTION: The decline in fertility rates is a concern for public health and it is partially explained by socio-economic factors, psychosocial stress and unhealthy lifestyle. Recent research has proposed that the intrauterine environment also determines fertility and it could be associated with maternal stress, through hormonal disturbance. Moreover, there is evidence from animal studies that the prenatal exposure of glucocorticoids is related to fertility impairments in the offspring. We hypothesized that prenatal stress due to maternal bereavement during pregnancy or the year before has a programming effect on adult reproductive impairments.

METHODS: This population-based cohort study considered all subjects born in Denmark after 1968 and Sweden after 1973 and older of 12 years at the end of follow-up (N=4,128,761). Children were categorized as exposed if their mothers lost a close relative during pregnancy or the year before and unexposed otherwise. The main outcome was the age of each subject when having the first child. Data was analyzed using Cox model stratifying by country and gender and adjusting for different covariates. Subanalyses were performed considering the type of relative and the timing of bereavement. We also took into consideration death as a possible competing event using a Fine-Gray model.

RESULTS: 93,635 children (2.3%) were exposed and 983,977 (23.8%) had a child during the follow-up time. For Swedish children, the hazard ratio (HR) and 95% confidence interval (CI) of having the first child was HR=0.98, CI: 0.95-1.02 for males and HR=1.01, CI: 0.98-1.03 for females. For Danish children, we found a HR=1.03, CI: 0.97-1.09 for males and HR=1.02, CI: 0.97-1.07 for females. Results did not change in any of the subanalyses performed.

CONCLUSIONS: We did not observe any substantial difference between subjects exposed to prenatal stress due to maternal bereavement and subjects unexposed when studying the age of having their first child.