Abstract
Serum PGF2α levels during labour and the early post-partum period have been determined by radioimmunoassay. Random samples from 81 women showed that the highest levels are found in the late first stage of labour with lower levels in the second stage, at delivery and post-partum. The pattern in seven women who were followed through labour was similar to that seen in random samples and it was found that the change in serum PGF2α levels appears to be related to the stage of cervical dilatation.