New mothers giving birth in a hospital face a danger many might not even consider. The time they give birth could seriously affect their odds of complications during delivery.

A study published in Risk Analysis: An International Journal found the number of delivery complications is higher at night, on weekends or holidays, and at teaching hospitals.

"We find consistent evidence of a sizable statistical relationship between deliveries during nonstandard schedules and negative patient outcomes," the study said.

Researchers at Colorado State University and the Department of Agriculture teamed with data specialists at Abt Associates to analyze more than 2 million births between 2005 and 2010 in Texas. They broke those down by work shift, hours worked within a shift, whether a birth was on a weekend or holiday, or if a birth happened in July, when teaching hospitals get new residents.

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They measured complications such as a “third- or fourth-degree perineal laceration, ruptured uterus, unplanned hysterectomy, admission to intensive care unit and unplanned operation procedure following delivery.”

The study found a delivering mother’s odds of facing a complication are 21.3 percent higher on the night shift. On weekends, the odds are 8.3 percent higher. On holidays, 29 percent.

Even during normal shifts, every hour staff works increases the mother’s odds of having a complication by 1.8 percent.

Delivering at a teaching hospital has 2.2 times greater risk than a regular hospital.

Researchers theorized hospitals could pair new physicians with experienced doctors to reduce errors, News Medical reported.

The study — titled “Clinical Capital and the Risk of Maternal Labor and Delivery Complications: Hospital Scheduling, Timing, and Cohort Turnover Effects” —was written by Sammy Zahran, David Mushinski and Hsueh-Hsiang Li of Colorado State University; Ian Breunig of Abt Associates Inc.; and Sophie McKee of the U.S. Department of Agriculture.