Steroid hormone levels in the peripartum period - differences caused by fetal sex and delivery type.

Progesterone, estrogens, androgens and glucocorticoids all play important roles during pregnancy, from implantation to delivery. Focusing on selected steroid hormones in the peripartum period, we defined reference ranges measured using LS-MS/MS, and assessed relationships with maternal age, pregnancy weight gain, delivery type, and fetal sex. Samples were taken from 142 healthy women with physiological gravidity at the 37th week, during the first period of labor, and from newborn mixed cord blood. We found higher cortisol and 17-OH-pregnenolone plasma levels in mothers at the 37th week that carried male fetuses (p=0.03), but no significant differences in any studied hormones in newborns of different sex. Neither maternal age nor weight gain nor newborn birth weight had any relationships to any of the studied hormones. However, there were differences depending on vaginal versus planned cesarean section deliveries. In women carrying a male fetus we found significantly higher levels of 17-OH-pregnenolone, progesterone, cortisol, corticosterone and significantly lower levels of estradiol in those undergoing spontaneous vaginal delivery. However, we found no significant differences in the cord blood of newborn males from either delivery type. We established reference ranges for our analysis methods, which should be useful for further studies as well as in standard clinical practice.