Objective To describe the effect of maternal age on diurnal rhythm to the onset of labour.

Design Retrospective review of labour and delivery data.

Setting A large United Kingdom maternity service.

Population Over the period of 10 years 30,022 eligible women delivered, of which 28,800 deliveries were studied.

Main outcome measures Maternal age and the timing of the onset of labour.

Methods A United Kingdom maternity department database was used to identify deliveries over a 10 year period and the time of onset of labour retrieved from these records. 28,800 labours were divided into five maternal age specific categories; <19, 20-24, 25-29, 30-34 and >35years and their rhythms compared.

Various biological rhythms pertaining to various organ systems have been described in literature and some of these rhythms change with increasing individual's age. Most profound being age related sleep disturbances. These changes have been demonstrated by changing EEG wave form with increasing age. Furthermore sleep and circadian rhythm also affect working of human immune system.

Interestingly this circadian output measured at the level of neural activity rhythms in the SCN is degraded by aging, and this decline occurs before the disruption of key components of the molecular clockwork.

Results No significant difference was noted (p=0.494) in the time of onset of labour when labourers were divided into five age specific categories and their rhythms plotted and compared.

Conclusions Maternal age has no effect on 24 hour rhythm to the onset of labour.