June 18 (HealthDay News) -- Job stress during early pregnancy increases the risk of low infant birth weight, a new study finds.

Dutch researchers analyzed responses from 8,266 pregnant women who filled out a questionnaire on employment and working conditions.

The study found that a work week of 32 hours or more and high job strain during the first trimester had an impact on an infant's birth weight. A combination of high job stress and a long work week was associated with the greatest birth-weight reduction and the highest risk of delivering a small-for-gestational-age baby.

"Although pregnant women typically reduce their working hours or workloads at the end of the pregnancy, our results suggest that reducing job strain and working hours in the initial stages of pregnancy may be beneficial among women with stressful full-time jobs," the researchers concluded.

The study appears online June 18 and in the August print issue of the American Journal of Public Health.

SOURCE: American Public Health Association, news release, June 18, 2009