A paper published Friday by the National Center for Health Statistics has showed that births of most babies take place on a weekday in the US. And the time window for most of these births is between 8am and 9am and from noon to 1 pm.

One of the major reasons behind this is that most births in the US are taking place in hospitals. Other factors are increase in C-sections and induced labor during the past few decades. Most deliveries are taking place during the day in a bid to have maximum coordination and care with doctors and hospital staff.

Less than 2% of births in the US take place outside the hospital. Most of the births outside hospitals are highly likely to take place in the wee morning hours between 1 am and 4:59 am, said the report.

There is a perception among some pregnant women that the middle of the night is an optimal time for delivery. But Aaron Caughey, chairman of the Department of Obstetrics and Gynecology at Oregon Health & Science University's School of Medicine, said giving birth in the middle of the night is full of danger for pregnant women as they can bleed to death.

Melissa Fries, chair of obstetrics and gynecology at MedStar Washington Hospital Center, said modern technology provides safer option for women to give birth.

About 21% of cesarean deliveries are performed nationally because the baby is in some kind of stress. “If you consider all hospitals, especially those that don't have the staffing in the middle of the night, you're going to see more complications [at night], whereas in the daytime, there are usually enough people in the hospital”, said Caughey.

The data has showed that not many American mothers are having late night surprises.