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 delivery. Design Maternal and cord blood specimens were collected at term after spontaneous 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, divided into two subgroups: group 1 vaginal delivery (n= 21), were delivered 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 higher 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 serum activin A and inhibin A concentrations did not show a significant difference between male and female infants in either vaginal or caesarean section, but male infants showed inhibin B levels significantly higher than female, independent of the mode of delivery. Conclusions In the presence of active labour, the human placenta secretes larger amounts of activin A and lesser amounts of inhibin A and inhibin B into the maternal circulation. Inhibin–related proteins in the fetal circulation do not show differences according to the mode of delivery, suggesting that they have a different method of production or metabolic rate compared with maternal activin and inhibins.