Activin A, inhibin A, inhibin B and parturition: changes of maternal and cord serum levels according to the mode of delivery

Objective To evaluate whether activin A, inhibin A, and inhibin B levels in maternal and umbilical artery serum change according to the mode of delive ry. Design Maternal and cord blood specimens were collected at term after spont aneous labour and vaginal delivery, or elective caesarean section. Setting Universities of Pisa, Turin, Naples and Udine. Population Forty-two healthy pregnant women, at 39-40 weeks of gestation, d ivided into two subgroups: group 1 vaginal delivery (n = 21), were delivere d of 10 female and 11 male infants; group 2 elective caesarean section (n = 21), were delivered of 11 female and 10 male infants. Main outcome measures Serum activin A, inhibin A, inhibin B concentrations in maternal and umbilical cord blood. Results At vaginal delivery, maternal serum inhibin A and inhibin B levels were lower and activin A levels higher than at elective caesarean section. Maternal levels of activin A, inhibin A and inhibin B were constantly highe r than in umbilical arterial blood, independent of the mode of delivery. No significant difference was observed in umbilical arterial serum levels of the three proteins between the two modes of delivery. Umbilical arterial se rum activin A and inhibin A concentrations did not show a significant diffe rence between male and female infants in either vaginal or caesarean sectio n, but male infants showed inhibin B levels significantly higher than femal e, independent of the mode of delivery. Conclusions In the presence of active labour, the human placenta secretes l arger amounts of activin A and lesser amounts of inhibin A and inhibin B in to the maternal circulation. Inhibin-related proteins in the fetal circulat ion do not show differences according to the mode of delivery, suggesting t hat they have a different method of production or metabolic rate compared w ith maternal activin and inhibins.