Overtime Work in Pregnancy May Affect Baby's Size

Dated: 2012-07-03

Amsterdam, July: A new study shows that pregnant women who spend a lot of time on their feet and work more than 40 hours a week may give birth to smaller babies.

The study shows that women who spent long periods on their feet during their pregnancy in jobs such as sales, child care, and teaching had babies whose heads were an average of 1 centimeter smaller than average at birth.

Clocking long hours during pregnancy also had an effect on the baby's birth weight. About half the women in the study worked between 25 and 39 hours a week. About one in four worked more than 40 hours a week.

The women who worked more than 40 hours a week had slightly smaller babies than those who worked less than 25 hours a week. But there were no differences in rates of preterm delivery, low birth weight, or babies being born too small for their gestational age, the study showed.

The differences in head size and weight were apparent from the third trimester onward.Whether or not these differences affect a baby's long-term development is not known. The findings appear online in Occupational and Environmental Medicine.The study suggests that changes are needed in work patterns for pregnant women.

"We believe that optimizing the work environment is important since participation of women in the reproductive age in the workforce continues to increase," the researchers write. The research team was led by Claudia A. Snijder, MD, of the Erasmus Medical Center in Rotterdam, the Netherlands.

Close to 40% of women spent a long time on their feet and 45.5% had to walk for long periods as part of their job, according to the study. Just 6% of women engaged in on-the-job heavy lifting. About 4% worked night shifts.

"Anecdotally, we have always known that women who work harder have smaller babies," says Cynthia Gyamfi, MD. She is the director of perinatal clinics and an associate clinical professor of obstetrics and gynecology at New York-Presbyterian Hospital/Columbia University Medical Center in New York City. Certain changes could help level the playing field for working moms and their kids, she says.

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