THE ASSOCIATION BETWEEN OCCUPATIONAL FACTORS AND PRETERM BIRTH - A UNITED-STATES NURSES STUDY

OBJECTIVE: Our purpose was to evaluate factors associated with preterm birth among a national sample of U.S. nurses. STUDY DESIGN: We conduc ted a case-control study of 210 nurses whose infants were delivered pr ematurely (<37 weeks) (cases) and 1260 nurses whose infants were deliv ered at term (greater than or equal to 37 weeks) (controls). An occupa tional fatigue score was constructed from four sources and varied from 0 to 4. The relation between occupational activity (including hours w orking and fatigue score) and preterm birth was analyzed with the use of Pearson chi(2) tests, estimates of adds ratios with 95% confidence intervals, and multivariate logistic regression; we controlled for con founding factors. RESULTS: Factors significantly associated with prete rm 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 exer tion (p = 0.01); and occupational fatigue score (p < 0.002). The adjus ted odds ratios were 1.6 (p = 0.006) for hours worked per week (less t han or equal to 36 vs > 36) and 1.4 (p = 0.02) for fatigue score <3 vs greater than or equal to 3. CONCLUSIONS: Preterm birth among working women may be related to hours worked per day or week and to adverse wo rking conditions.