Does natural birth have a circadian rhythm?

The aim of this study was to investigate whether natural birth has a circadian rhythm. The present study was planned as a retrospective descriptive study of the natural births performed in a Maternity and Children's Diseases Training and Research Hospital in the north of Turkey between January 1 and December 31. The study included 723 (98.9%) cases of natural birth. It was found that the mean age of the women in the study sample was 26.84 ± 5.83 years and the mean gestational age was 38.98 ± 1.95 years. It was determined that the mean labour duration of the women was 12.47 ± 0.78 hours; of all births, 34.6% occurred between 08:00-16:00 hours, 38.2% occurred between 16:01-00:00 hours and 27.2% occurred between 00:01-07:59 hours. Considering the birth time in terms of month, it was observed that the most common birth month was July and the least common birth month was March. In accordance with the study data, it is observed that the labour process occurred at night in the day/night cycle and in the summer months at a higher rate.Impact statementWhat is already known on this subject? Chronological transitions are of critical importance for pregnancy. There are many mechanisms affecting Labour process. One of the most important mechanisms among these is the release and timing of foetal-maternal hormones. The chronological transitions are critical for a normal pregnancy and any temporary alteration may have detrimental effects for foetal development and/or maternal healthWhat the results of this study add? It is observed that births occur at a higher rate at night hours in the day-night cycle and in summer months, and in terms of day, Wednesday is the most common birth day. Considering these results, although it is thought that the levels of hormones released at night lead the birth to occur mostly at night-time hours and non-fully developed thermoregulatory system and sympathetic nervous systems of foetus and sensitivity to temperature may be effective on the number of births in summer months, it is seen that the data are insufficient to reach this conclusion.What the implications are of these findings for clinical practice and/or further research? It is believed that the foetus has a biological clock. This is parallel to fluctuating levels of various hormones affecting labour and delivery, which may be a positive influence on the labour process itself. It seems that more study results are required in addition to these results.