Psychological distress during early gestation and offspring sex ratio.

BACKGROUND Exposure to severe stress in early pregnancy is associated with a lower male to female ratio (sex ratio), but whether more moderate levels of psychological discomfort have the same kind of effect is unknown. In a population based follow-up study, we aimed to test whether psychological distress was associated with the sex ratio in the offspring. METHODS From 1989 to 1992, a cohort of 8,719 Danish-speaking pregnant women were followed until delivery. Questionnaires were administered to the women in early pregnancy and 6,629 (76%) completed the 30-item version of the General Health Questionnaire (GHQ). RESULTS We found an overall male to female ratio (sex ratio) of 1.03. There was an inverse dose response association (test for trend P < 0.01) between GHQ score and sex ratio. Each 5-point increase in the GHQ score was associated with a decreasing odds of having a boy [Odds ratio (OR) = 0.93, 95% CI 0.89-0.98]. Mothers scoring in the upper quartile of the GHQ had 47% boys as compared with 52% in the undistressed groups (Risk difference =4.8%, 95% CI 1.9-7.7%) resulting in a significantly lower sex ratio of 0.85 compared with 1.07 (OR 0.82, 95% CI 0.72-0.94). CONCLUSIONS Our results suggest that not only severe stress, but also more moderate and common levels of psychological distress, may decrease the sex ratio in the offspring. Stress during pregnancy is a likely candidate involved in the decreasing sex ratio observed in many countries.