April 5, 2000 (Atlanta) -- Physically taxing work conditions -- like prolonged standing, heavy lifting, and night work -- may increase a woman's risk of having a problem pregnancy, say researchers who reviewed many studies of the issue.
The risks of such work, the researchers found, include premature babies, babies that are small for their gestational age, and high blood pressure in the mothers.
The researchers, who reviewed 29 studies of the issue involving more than 160,000 working women, say their findings lend support to the need for an improved national maternity leave policy -- one that includes pay, health benefits, and job security for all.
"Preterm birth is a huge problem," study author Ellen Mozurkewich, MD, tells WebMD. "There have been a lot of advances in obstetrics over the last 50 years that have drastically reduced maternal death and [injury] ... and fetal and neonatal death.
"But the big remaining problem is preterm birth. The reason it is such a large problem is -- even though the risk of death related to premature delivery has decreased markedly -- there are still major long-term problems that can result for the children." Mozurkewich is an obstetrician-gynecologist who is receiving additional training in complicated pregnancies at the University of Michigan Medical School in Ann Arbor.
Mozurkewich and her colleagues looked at the link between preterm births -- those that occur at 20 to 36 weeks' gestation -- and physically demanding work (that including heavy or repeated lifting or carrying, manual labor, or significant exertion); prolonged standing; shift work; and long working hours.
They also looked at the relationship between these conditions and a woman's risk for having a small baby, or developing high blood pressure or a pregnancy-related condition known as preeclampsia (high blood pressure, swelling, and protein in the urine). A woman was considered to have been exposed to risky work conditions if the conditions lasted at least through the second trimester.
They found that physically demanding work was associated with having premature or small babies. It was also linked to high blood pressure or preeclampsia in some mothers. Other conditions associated with preterm birth included high levels of work fatigue, prolonged standing, and night work. Working long hours was not significantly associated with preterm birth, according to the authors.
Even a relatively small increase in the risk of preterm birth is important, Mozurkewich says. "There have been a lot of studies looking at possible ways of preventing preterm birth and, for the most part, they have come up empty handed," she says. "[Working conditions] may not be the largest contributor to preterm birth in the United States, but it is another contributor."
Because many conditions can lead to premature labor or delivery, poor growth of the baby before birth, and high blood pressure, a woman should talk with her obstetrician or pregnancy specialist about whether special precautions may be needed in her case.
"Our association suggests that modifying these lifestyle factors on the job may reduce a woman's risk of preterm birth," Mozurkewich tells WebMD. "But I would emphasize that liberalizing leave policies may be necessary; it is very difficult for many women to modify activities on the job. It is much easier said than done."
- Physically taxing work conditions can increase the risk of a woman having problems with pregnancy, such as preterm birth, babies that are small for gestational age, and high blood pressure or preeclampsia.
- Work conditions that were associated with these problems included prolonged standing, heavy lifting, and shift work, but working long hours did not show an association.
- Preterm birth can cause major long-term problems in children, so women may want to consider modifying lifestyle factors on the job and employers may want to implement better maternity leave policies.