Maternal serum total activin A and follistatin in pregnancy and parturition

To examine changes in maternal serum levels of activin A and follistatin during pregnancy and labour.

In three cross sectional and three longitudinal studies venous blood was collected from women during pregnancy, spontaneous labour, labour induction and prior to elective caesarean section for the measurement of activin A and follistatin.

Monash Medical Centre, Clayton, Victoria, Australia.

One hundred and twenty-three women participated in a cross sectional study in pregnancy, 18 women in two longitudinal pregnancy studies, 36 women in a cross sectional labour study, nine women in a longitudinal study of labour induction. Ten women undergoing elective caesarean section were also studied.

Activin A and follistatin were measured using two sensitive and specific enzyme-linked immunosorbent assays.

In the cross sectional study of pregnancy, mean (SEM) maternal serum activin A and follistatin levels increased towards term (2.4 ng/mL (0.3) and 1.8 ng/mL (0.3) in first trimester to 18.9 ng/mL (3.8) and 5.3 ng/mL (0.9) at term, respectively), but the longitudinal study revealed that levels plateau in the last three weeks of pregnancy (16.0 ng/mL (2.6) and 6.2 ng/mL (1.4) at 37 weeks and 16.6 ng/mL (3.5) and 6.2 ng/mL (0.5) before labour for activin A and follistatin, respectively). There was no difference in levels of activin A and follistatin between women delivered by caesarean section and labouring women at term (14.9 ng/mL (2.8) vs 11.0 ng/mL (0.93) and 5.95 ng/mL (0.67) vs 5.71 ng/mL (0.63), respectively) and levels of both proteins did not alter throughout spontaneous or induced labour.

We believe that these data argue against activin A playing an acute role in the initiation or regulation of human parturition.