24-hour rhythm to the onset of term and preterm labour in twin pregnancies.

Abstract

The objective of this study is to describe the time of onset of contractions in twin pregnancies that result in delivery, so as to investigate whether there is a diurnal influence. A UK maternity department database was used to identify twin deliveries over a 5-year period, and the time of onset of labour was retrieved from these records. Two hundred and eleven women with spontaneous onset of labour in twin pregnancies were studied. A significant diurnal rhythm in the timing of contractions was noted, with 45% of deliveries occurring in labour that commenced between midnight and 08.00 hours. This periodicity is similar for twin pregnancies that end in preterm (24-36 weeks of gestation; χ² = 17.2; P < 0.01) or term deliveries (37-40 weeks of gestation; χ² = 13; P < 0.05). The periodicity of onset of labour in multiple pregnancies demonstrates a similar rhythm to singleton pregnancies, where labour most commonly begins between midnight and 08.00 hours.