Hair cortisol levels in pregnancy as a possible determinant of fetal sex: a longitudinal study

Stress during pregnancy has been widely studied and associated to different variables, usually with negative results for the health of the mother and the newborn, such as having a higher risk of suffering postpartum depression, premature birth, obstetrics complications or low birthweight, among others. However, there are not many lines of research that study the role that the sex of the baby plays on this specific stress and vice versa. Thus, the main objective was to analyse the relationship between the sex of the offspring and the stress of the mothers in the first trimester of pregnancy. In order to achieve this, 108 women had their biological stress measured (trough hair cortisol levels) and psychological stress evaluated (the Prenatal Distress Questionnaire (PSS), the Perceived Stress Scale (PDQ) and the Stress Vulnerability Inventory (IVE)). The results revealed significant differences in maternal hair cortisol levels in the first trimester based on the sex of the baby they had given birth to (t = −2.04; P < 0.05): the concentration of the hormone was higher if the baby was a girl (164.36: 54.45-284.87 pg/mg) than if it was a boy (101.13:37.95-193.56 pg/mg). These findings show that the sex of the future baby could be conditioned, among many other variables, by the mother´s stress levels during conception and first weeks of pregnancy. Further research is needed in this area to support our findings.
Frontier Project “A-CTS-229-UGR18” of the Ministry of Economy, Knowledge, Business and University of the Junta de Andalucía
European Regional Development Fund (ERDF)
Spanish Ministry of Science, Innovation and Universities, FPU program, reference number 18/00617
(Spanish Ministry of Economy, Industry and Competitiveness, FPI Program, reference number BES-2016-077619