Diurnal variation in admission to hospital of women in labour.

In women having spontaneous labour or premature rupture of the membranes there is a marked diurnal variation in times of admission to hospital. Analysis of 4755 nulliparous women with single pregnancies in cephalic presentation at term, indicated that they presented in labour or with premature rupture of the membranes nearly twice as frequently during the night as during the evening. The peak hours for delivery were late morning and afternoon. The authors discuss previously published reports of similar findings and of a diurnal variation in maternal hormone levels in humans and experimental animals. The potential clinical importance of this phenomenon is considered.