Hard Work When Carrying a Baby

Pregnant women working long hours or on their feet a lot have slightly smaller babies

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) While a certain amount of physical activity is healthy during pregnancy, women have to be careful not to overexert themselves. Finding that line can be tough in a demanding job.

A recent study found that spending a lot of time on your feet or working long hours while pregnant can have a very small, but measurable, effect on your baby's weight and head circumference.

"Follow your OB/GYN's or midwife's advice regarding activity levels during pregnancy."

Claudia A. Snijder, PhD, of Erasmus Medical Center in the Netherlands, and colleagues investigated the association between physically demanding work during pregnancy and the growth of these working women's babies in the womb.

They gave 4,680 pregnant women a questionnaire to fill out midway through their pregnancy. They included employed mothers of single children, not multiples, and conducted the study from 2002 to 2006.

The questionnaires asked about the women's physical workload and how much time they spent lifting, walking and standing for lengthy periods. They also asked how many night shifts women worked and what their working hours were.

Over the course of the women's pregnancies, the researchers used sonograms to measure the growth of the women's babies. They also measured the babies at birth.

About 39 percent of the women were on their feet a lot, and 46 percent spent a lot of their time walking. Only a small percentage (6 percent) had to do heavy lifting or worked night shifts (4 percent).

No link was found between physically demanding work or the women's scheduled working hours and any patterns in babies' size, birth weight or likelihood of being born early.

The babies of women who had spent long periods of time standing or being on their feet in general, had smaller head circumferences by about 1 cm, or 3 percent of an average baby's head circumference at birth. These women tended to work in jobs like sales, teaching and childcare.

Further, the babies of women who worked 25 or more hours per week had lower growth rates in terms of their weight as a fetus and their head circumference as compared to the babies of women who worked less than 25 hours a week. The babies' heads were an average 1 cm smaller at birth, and they were approximately 5 to 7 ounces lighter.

The link the researchers found was between a baby's growth in the womb and the mother's standing for long periods or working longer hours each week.

These findings, however, do not offer any cause for alarm about any particular activities, pointed out Sharon Thompson, MD, MPH, of Central Phoenix Obstetrics and Gynecology in Arizona. Dr. Thompson, who was not associated with this study, told dailyRx that most of the study's findings revealed no link between physically demanding work or long work hours and adverse birth outcomes.

"None of the variables studied was associated with the outcomes that obstetricians and pediatricians worry about--small for gestational age and preterm birth," Dr. Thompson said. The only finding - the 3 percent smaller head circumference - is small, and it's unclear what the significance of it is, she said.

"The authors go on to discuss this finding in a lot of detail in the discussion but this finding does not change any recommendations for activity during pregnancy," Dr. Thompson said.

Additionally, the background research noted that working women tend to have fewer complications with their pregnancies as well as fewer birth defects and stillbirths than unemployed women.

Research has also shown an increased risk of birth defects, premature birth, stillbirth and low birth weight in babies whose mothers worked long hours during their pregnancy, according to the paper's background information, though it did not provide specifics.

The study was published online June 27 in Occupational and Environmental Medicine. The research was supported by the Erasmus Medical Center, the Erasmus University Rotterdam, the Netherlands Organization for Health Research and Development, the Netherlands Organization for Scientific Research, the Netherlands Ministry of Youth and Families and the Netherlands Ministry of Health, Welfare and Sport.

The study also received funding from the European Union's Seventh Framework Program for Research and Technology Development. The authors declare no competing interests.

Reviewed by: 
Review Date: 
June 29, 2012
Last Updated:
November 20, 2012