This is the most common time women give birth. And the reason why makes a lot of sense.

You know how it happens in the movies – a heavily pregnant woman wakes up to painful contractions in the middle of the night. After the whole household is woken up, there’s a madcap dash to the hospital in pyjamas.

But what is the most common time for women to give birth? Now it turns out that art imitates life much more than we realised.

New research, conducted over a ten year period in the United Kingdom by the City University of London, in collaboration with University College London (UCL) and the National Childbirth Trust (NCT), analysed more than five million births, and has found that the most common time to give birth is 4am.

Perhaps that’s Mother Nature’s way of preparing parents for the rude shock of sleepless nights ahead?

The statistics show that 71.5% of births take place outside of civilised business hours – in fact, between the hours of 1am, and 6:59am – on weekends, public holidays, or between 5pm – 8:59am on non-holiday weekdays.

And more than half of the births that happen in those hours were the result of spontaneous labour.

All parents remember this moment: exhausted, but it's all worth it. Source: Supplied.

The researchers found just over a quarter (28.5%) of births occurred between 9am and 4:59pm on weekdays, while almost three quarters (71.5%) took place outside these hours at weekends, on public holidays or between 5pm and 8:59am on non-holiday weekdays.

Elective or pre-planned caesarean births accounted for 9.2%, and happened largely on weekdays between 9am and 11:59am - which would make sense, considering hospital staff rosters.

Lead researcher Dr. Peter Martin said:

“Long-term experience and research from other areas has shown that human births without obstetric intervention are most likely to occur at night or in the early hours of the morning."

His explanation? Evolution.

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

Mamamia spoke to Melbourne obstetrician Dr. Philippa Costley, who said Dr. Martin's theory is "an interesting one." But, as she explains further:

"In my experience, the rate of onset of spontaneous labour is higher at night. We're still not sure of the exact mechanism behind this. There is some evidence that melatonin (the hormone that enhances sleep) may work in conjunction with the hormones of labour, such as oxytocin. However, the exact relationship is unclear at this time."