Effect of relaxin on prostaglandin E production by human amnion: changes in relation to the onset of labour

Abstract

The effect of relaxin on prostaglandin E (PGE) production by human amnion in vitro was investigated. When amniotic discs were incubated in the presence of increasing concentrations of relaxin, two distinct effects were observed. Discs prepared from women delivered by caesarean section before the onset of labour showed a significant decrease in PGE output at relaxin concentrations of 0.5-2 micrograms/ml; the effect was abolished at higher relaxin concentrations. Discs obtained from women delivered after labour of spontaneous onset responded to the addition of relaxin (4-8 micrograms/ml) with a significant increase in PGE output, although this increase was only evident in patients in whom labour had started with intact membranes. These results suggest that relaxin, which is present in decidua and chorion laeve at term, may have a paracrine effect on the amnion, inhibiting PGE production during continuing pregnancy but favouring its production during spontaneous labour.