Immunoreactive endorphin peptides in amniotic fluid during labour.

Immunoreactive endorphin peptides (irEP) were measured in term amniotic fluids at induction by amniotomy (n = 8), during early and late first stage of labour (n = 52), at vaginal delivery (n = 30) and at caesarean section (n = 10). Individual values ranged from 50 to 222 pg/ml, but mean values did not differ significantly, and serial determinations revealed that irEP in the amniotic fluid remained almost constant in each woman from the first stage of labour through to delivery. There was no correlation between pathological changes in the cardiotocogram or low umbilical artery pH and irEP levels in the amniotic fluid at vaginal delivery. We conclude that immunoreactive endorphin peptides in the amniotic fluid probably are of fetal or placental origin and do not reflect fetal wellbeing or distress.