Objective The objective of this study was to assess the relation of some maternal job characteristics to the risks of delivering a small-for-gestational-age or preterm infant.

Methods Altogether 4390 women who lived in Quebec City, Canada, and the surrounding area, and who gave birth between January and October 1989 to a singleton liveborn neonate were included. Information on gestational age at delivery, job characteristics, nonoccupational physical activities, and several potential confounders was obtained in a telephone interview a few weeks after the delivery. Birthweight was recorded from the birth certificate.

Results The risk of having a small-for-gestational-age infant (birthweight lower than the 10th percentile for gestational age and gender) was increased among the women who worked at least 6 h a day in a standing position. The adjusted odds ratios (OR) were 1.00, 1.13 [95% confidence interval (95% CI) 0.83--1.55], and 1.42 (95% CI 1.02--1.95) for the women working in a standing position <3, 3--5, and 6 h a day, respectively. The risk for a small-for-gestational-age infant also slightly increased as the gestational age at work cessation increased. A modest increment in the risk of delivering preterm (OR 1.45, 95% CI 0.84--2.49) was observed for the women working regularly in the evening or at night. Physical effort, lifting heavy objects, and long workhours were not related to either a small-for-gestational-age or a preterm infant. Conclusions The results indicate that prolonged standing and working late into pregnancy may increase the risk of delivering a small-for-gestational-age infant, whereas regular evening or night work may be a risk factor for preterm birth.

Key terms fetal growth; maternal employment; pregnancy outcome; preterm birth