Noisy, tiring jobs that involve lots of standing and long hours can raise a pregnant woman’s risk of premature delivery, according to a new study released Friday.
Researchers from the University of Michigan Medical Center, whose work appears in the September issue of the American Journal of Obstetrics and Gynecology, studied 210 nurses whose babies were born prematurely - before 37 weeks of pregnancy - and 1,260 other nurses who gave birth to full-term, 40-week infants.
The researchers compared nurses in stressful jobs - those who stood for long hours to care for patients, worked in noisy environments or worked long shifts in physically demanding jobs - to those with quieter, desk jobs, and found a significantly higher risk of prematurity in the high-stress group.
Standing, they found, was the single most important risk factor. Women who stood for four to six hours a day increased the risk of prematurity by 80 percent compared to women who stood for less than four hours. Standing for more than six hours tripled the risk.
Women who said their jobs left them somewhat tired at the end of the day also raised their risk 30 percent, while those whose jobs left them “extremely tired” more than doubled their risk. Physical exertion, such as lifting and carrying, also increased the risk 40 percent.
Moderately loud noise in the workplace similarly increased risk 50 percent. And extremely loud noise - like that found in neonatal intensive care units, where machines whir constantly and babies cry - doubled the risk.
Furthermore, these risks go up for women who have a history of premature deliveries, the researchers said. A woman who has had one premature baby is at three times greater risk of having a subsequent baby prematurely.
Does this mean pregnant women who need or want to keep working through pregnancy should throw up their hands and quit?
“Not at all,” said Luke. But women “should talk to their obstetricians about their work and home environments and they should talk to their employers.”
Preventive measures to reduce the risk of prematurity, she said, include reducing work hours per week or per shift, redesigning work to make it less strenuous and granting leaves during pregnancy, especially for women with complications.
Overall, she noted, prematurity has risen 20 percent in the last decade, “in part because the number of employed women in the United States has doubled in the past 35 years.”
Prematurity now occurs in one in 10 American births.
But other countries, she noted, have lower prematurity rates. In France, she said, women have been taught to connect signs of premature labor to physical activity - and only 4 percent of pregnant women have premature babies.
In fact, Luke says, vigorous exercise “is not good for pregnant women,” though others are not so sure.
A 1994 statement by the American College of Obstetricians and Gynecologists notes, “In the absence of obstetrical or medical complications, pregnant women can continue to exercise and derive related benefits. Women who have achieved cardiovascular fitness prior to pregnancy should be able to safely maintain that level of fitness throughout pregnancy and the postpartum period.”
Added Cindy Pearson, program director for the National Women’s Health Network: “Pregnancy for most women is normal, and most women have found they are able to go about their normal business, which includes women in active professions. … In general, we believe most women can keep doing most jobs.”
ILLUSTRATION: Graphic: Unborn babies and the workplace
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