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

ObjectiveTo study the association between salivary stress biomarkers and the secondary sex ratio.DesignProspective, longitudinal cohort study.SettingCommunity 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 α-amylase and the 2° sex ratio, though not statistically significant.Conclusion(s)Our findings are consistent with a reversal in the 2° 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.