According to the new study, researchers have found that the time and day that women give birth can vary significantly depending on how labor starts and the mode of giving birth

Conducting the first national analysis to look at all aspects of time of birth in England, researchers from City, the University of London in collaboration with UCL (University College London) and the NCT, the UK's largest parents' charity, analyzed over five million births over a ten year period in England. 

Induced labors may lead to spontaneous births, operative births using forceps or ventouse or emergency caesareans. These three groups of induced births share a weekly cycle that has its highest peak on Friday night and its trough on Monday morning.

To investigate the time of birth, how labor starts and the mode of giving birth, the researchers linked data from birth registration, birth notification, and Maternity Hospital Episode Statistics and analyzed 5,093,615 singleton births in NHS maternity units in England over a ten-year period from 2005 to 2014.

They then used statistical analysis to establish how patterns of the timing of birth vary by mode of a start of labor, mode of giving birth and gestational age. The study is published in PLOS ONE.

Timing of birth

Patterns of spontaneous birth have remained unchanged in England since the 1950s, were documented in the nineteenth century and probably have a much longer history, but the researchers found that overall patterns of birth have changed since the 1950s, following the rise in rates of obstetric intervention from the latter half of the twentieth century onwards.

Professor Alison Macfarlane, senior author of the paper, and Professor of Perinatal Health at City, University of London, said: "It is known that obstetric intervention can influence the time of birth, but no previous analysis at a national level in England has yet investigated in detail how the day and time of birth varies by how labor starts and how women give birth."

"Pronounced differences were seen depending on how labor started and the mode of giving birth, with 71.5% of births overall occurring outside the hours of 9.00 to 4.59pm. Current trends in an obstetric intervention at birth may work in opposite directions." 

Rates of induction are now rising, and induced births are more likely to occur at night, while rates of pre-planned caesareans are also rising and these are likely to be scheduled for morning hours.

"The research should be of interest to policymakers, as policies to increase community births may lower rates of obstetric intervention and affect these trends and impact on the overall timing of birth."

Dr. Peter Martin, the lead author of the paper, said: "Long-term experience and research from other areas have shown that human births without obstetric intervention are most likely to occur at night or in the early hours of the morning. This may be part of our evolutionary heritage."

"Our ancestors lived in groups that were active and dispersed during the day and came together to rest at night. So night-time labor and birth probably afforded the mother and newborn baby some protection," he added.

Elizabeth Duff, Senior Policy Adviser, NCT, said: "This study tells us parents aren't bothered about the timing of the birth as long as it results in healthy mums and babies. So it's worrying that induction appears to be timed so that the babies are most frequently born around midnight when senior staff is less widely available to assist if complications arise.

"These findings should be acted upon by NHS managers to ensure their services provide women and babies with the best care at the right time."