A decline in prolactin levels in amniotic fluid and decidua at term pregnancy after the initiation of labour.

Prolactin is known to inhibit the production of prostaglandins, key substances in the initiation of labour. To explore a possible role of prolactin in human parturition, prolactin levels were therefore measured in amniotic fluid and decidua at full-term pregnancy. Prolactin levels in amniotic fluid before labour were about three times higher than those at labour and they tended to decrease with time during labour. Prolactin levels in decidua before labour were about twice as high as those at labour. These findings suggest a possible involvement of prolactin in human parturition.