Working Conditions and Adverse Pregnancy Outcome: A Meta-Analysis


Synopsis: Physically demanding work increases a woman’s likelihood of an adverse pregnancy outcome.

Source: Mozurkewich EL, et al. Obstet Gynecol 2000;95:623-635.

During the past several years, a number of articles have appeared in the English literature that have explored the role of working conditions on the outcome of pregnancy. Mozurkewich and associates of this article reviewed the published English literature through 1999 and performed a careful meta-analysis.

Mozurkewich et al examined only the following work related exposures: physically demanding work, prolonged standing, long work hours, shift work, and work fatigue score. The outcomes they investigated included: preterm birth, hypertension, preeclampsia, and small for gestational age (SGA) birth.

Mozurkewich et al performed appropriate inclusions and exclusions of published articles. They attempted to use raw data rather than statistically adjusted data.

The results of the meta-analysis were clear: physically demanding work was associated both with preterm birth and hypertension/preeclampsia. Preterm birth was also associated with prolonged standing and shift (night) work. There was no association with long work hours and premature birth. The identified increased risks were moderate. For example, physically demanding work was associated with a 22% increased risk of preterm birth, a 37% increased risk of SGA, and a 60% increased risk for hypertension or preeclampsia. Mozurkewich et al conclude that it is possible that the preterm births might be decreased by changing women’s work habits, but that prospective trials would be needed to determine whether a true benefit could be achieved.


Very often when I review an article that I think is excellent, I suggest to all readers that they obtain the article and review it. In this case, I specifically suggest that you do not try to read this article unless you are a study design nerd, like me. The article is included at the very back of the April issue of Obstetrics & Gynecology and is written in a way that makes it almost impossible to understand unless you love study methodology. Unfortunately, such writing style is absolutely essential for a good meta-analysis. Far too many articles have been published that claim to use the meta-analysis technique but fall far short.

Overall, this article is important. Based on what is now overwhelming evidence, it appears that hard physical work and long periods of standing adversely affect pregnancy outcome. Women who take part in such activities during pregnancy are about 20-30% more likely to have a preterm birth, an SGA infant, or (probably) a hypertensive disorder. Since work is one of the very few modifiable adverse conditions during pregnancy which is associated with poor outcomes, it could be argued that all of us (health care providers, work place managers, pregnant women, and government) should be more aggressive in our attempts to have pregnant women reassigned to less strenuous work. Obviously, this issue is large, expensive, and controversial. However, at the very least, we should be telling our pregnant patients who participate in strenuous work activities that they have an increased risk of an adverse pregnancy outcome.

According to the article by Mozurkewich et al, which of the following activities was not associated with an increase in adverse pregnancy outcome?

a. Physically demanding work

b. Prolonged standing

c. Shift (night) work

d. Long work hours