Changes in maternal placental growth factor levels during term labour

Placental growth factor (PlGF) has important angiogenic function that is critical to placental development. Lower levels of PlGF are associated with fetal growth restriction, pre-eclampsia and intrapartum fetal compromise. The aim of this study was to investigate the effect of labour on maternal PlGF levels.

This was a prospective observational cohort study. Normotensive women with a singleton, normally grown, non-anomalous, fetus between 37 + 0 and 42 + 0 weeks gestation were eligible for inclusion. PlGF was assayed at two time-points in labour. Women undergoing elective caesarean section served as controls. The primary outcome was the intrapartum change in maternal PlGF levels.

Fifty-nine labouring and 43 non-labouring participants were included. Median PlGF decreased from 105.5 pg/mL to 80.9 pg/mL during labour (-23.9%, p < 0.001). PlGF levels were significantly lower in the second stage of labour irrespective of onset of labour, parity, mode of birth or gestation ≥40 weeks. Compared to multiparous women, nulliparous women had significantly lower PlGF levels at both time-points but had similar overall decline in PlGF. Women who required operative vaginal delivery or emergency caesarean section had lower median PlGF levels at both PlGF time-points and greater drop in PlGF during labour compared to spontaneous vaginal deliveries but these were not statistically significant. No correlation was observed between duration of labour and decline in PlGF levels.

Overall, median PlGF levels fall by nearly one quarter during labour. This decline may reflect deteriorating placental function during labour.