Moving inductions to early morning could shorten labour by 6 hours

The best time to induce labour is in the early morning, research suggests. By aligning with our natural body clocks, early-morning inductions seem to shorten labour times and reduce the need for Caesarean sections.

“It’s a simple, no-cost approach that could make the experience better for everyone – the mother, the baby and the medical staff,” says Hanne Hoffmann at Michigan State University.

About a third of labours in the UK, the US and Australia are now induced, meaning they are brought on with medication or other artificial means, rather than waiting for them to start on their own. Inductions are commonly recommended if a baby is overdue or has issues with its growth, since prompt delivery reduces the risk of stillbirth. Other reasons include the waters breaking without initiating labour, which can increase the risk of infection.

The problem is that induced labours are often more drawn out than those that occur spontaneously. “I’ve had friends who’ve been induced and they’ve been in labour for two days. I was just blown away by how long and painful it was for them,” says Hoffmann.

This led Hoffmann – who studies circadian rhythms, natural oscillations in the activity of our tissues, driven by internal clocks – to wonder whether there might be an optimum time of day for inducing labour. “We know that spontaneous labour follows circadian patterns because uterine contractions tend to peak in the late evening, and we primarily give birth at night,” she says. This pattern may have evolved because there is less threat from predators at night.

To learn more, Hoffmann and her colleagues analysed records of more than 3000 induced labours conducted at a hospital in Michigan between 2019 and 2022. They found that the shortest labours were those induced between 3am and 9am. For example, those induced at 5am lasted for 15 hours on average, whereas those induced at 11pm lasted a staggering 6 hours longer, about 21 hours on average. The shorter morning-inducted labours were also less likely to lead to emergency Caesarean sections.

The reason for this early-morning benefit may be that receptors in the uterus are more responsive to the hormone oxytocin at this time. In spontaneous labour, oxytocin is responsible for stimulating uterine contractions. In inductions, a synthetic form of oxytocin is usually given to achieve the same effect. “When doctors induce labour with a big oxytocin bolus, it might be high-fiving the body’s own built-in morning oxytocin party, giving contractions an extra enthusiastic push,” says Satchidananda Panda at the Salk Institute for Biological Studies in San Diego, California.

The researchers also found that people with a high body mass index or who were giving birth for the first time appeared to benefit most from early-morning induction. They now plan to investigate the underlying biological mechanisms.

While it may not be practical for hospitals to schedule all inductions between 3am and 9am, they could consider prioritising first-time mothers and those who are overweight or obese, says Hoffmann.

Importantly, the study didn’t find any medical complications associated with inducing early in the day. “There were no increased risks of admissions to the NICU [neonatal intensive care unit] or other adverse outcomes,” says team member Rene Cortese at the University of Kansas Medical Center. “This is another important message of the study: you’re mitigating one risk but not creating another.”

The team now hopes to conduct a study to confirm that assigning pregnant people to early-morning inductions does indeed improve their labours. “We need to do a proof of concept study to make sure we can replicate this [finding],” says Hoffmann.

Other chronotherapies – medical interventions that are timed to align with circadian rhythms – are also being explored in the fields of oncology, cardiology and psychiatry. For example, a recent study found that treating cancer before 3pm could help patients live longer.