Objective: Our purpose was to evaluate factors associated with preterm birth among a national sample of U.S. nurses.
Study design: We conducted a case-control study of 210 nurses whose infants were delivered prematurely (< 37 weeks) (cases) and 1260 nurses whose infants were delivered at term (> or = 37 weeks) (controls). An occupational fatigue score was constructed from four sources and varied from 0 to 4. The relation between occupational activity (including hours working and fatigue score) and preterm birth was analyzed with the use of Pearson chi 2 tests, estimates of odds ratios with 95% confidence intervals, and multivariate logistic regression; we controlled for confounding factors.
Results: Factors significantly associated with preterm birth included hours worked per week (p < 0.002), per shift (p < 0.001), and while standing (p < 0.001); noise (p = 0.005); physical exertion (p = 0.01); and occupational fatigue score (p < 0.002). The adjusted odds ratios were 1.6 (p = 0.006) for hours worked per week (< or = 36 vs > 36) and 1.4 (p = 0.02) for fatigue score < 3 vs > or = 3.
Conclusions: Preterm birth among working women may be related to hours worked per day or week and to adverse working conditions.