Preconception stress and the secondary sex ratio: a prospective cohort study

Objective: To study the association between salivary stress biomarkers and the secondary sex ratio. Design: Prospective, longitudinal cohort study. Setting: Community setting in the United Kingdom. Patient(s): On discontinuation of contraception for purposes of becoming pregnant, 338 women aged 18-40 years with complete data (90%) were followed until pregnant or up to six menstrual cycles. Intervention(s): None. Main Outcome Measure(s): Secondary sex ratio. Result(s): Human chorionic gonadotropin pregnancies were detected in 207 (61%) women of whom 130 (63%) delivered singleton infants with available gender data. The adjusted odds ratio for a male birth was decreased for women in the highest quartile (AOR = 0.26; 95% confidence interval = 0.09, 0.74) of salivary cortisol relative to women in the lowest quartile during cycle 1. An inverse relation was observed between a-amylase and the 2 degrees sex ratio, though not statistically significant. Conclusion(s): Our findings are consistent with a reversal in the 2 degrees sex ratio with increasing preconception salivary cortisol concentrations. This relation suggests that activation of the hypothalamus-pituitary-adrenal axis may have implications in sex allocation and requires further study. (Fertil Steril (R) 2012;98:937-41. (C)2012 by American Society for Reproductive Medicine.)