Work as a nurse and a midwife and adverse pregnancy outcomes: a Finnish nationwide population-based study.

OBJECTIVE: To assess whether work as a nurse and a midwife during pregnancy increases the risk of adverse pregnancy outcomes. METHODS: We identified from the 1990-2006 Finnish Medical Birth Registry all singleton births to nurses (n=109,542), midwives (n=3,009), and teachers (n=23,454) (referents). The main outcomes were sexual differentiation, low and high birth weight, preterm and postterm delivery, small and large for gestational age, and perinatal death. RESULTS: The prevalence of low birth weight (2.9% vs. 2.5%), preterm delivery (4.4% vs. 4.1%), postterm delivery (4.7% vs. 4.1%), small for gestational age (1.8% vs. 1.4%), perinatal death (0.45% vs. 0.41%) and stillbirth (0.30% vs. 0.25%) was higher among the newborns of nurses than those of teachers. The adjusted odds ratio (OR) from generalized estimating equations was 1.17 (95% confidence interval [CI] 1.07-1.26) for low birth weight, 1.09 (95% CI 1.02-1.16) for preterm delivery, 1.11 (95% CI 1.03-1.18) for postterm delivery, 1.17 (95% CI 1.05-1.30) for small for gestational age, 1.12 (95% CI 0.90-1.35) for perinatal death, and 1.27 (95% CI 0.98-1.56) for stillbirth. For midwives, the risk of small for gestational age (OR=1.25, 95% CI 0.95-1.55) was elevated, but the 95% CI included unity. There was no substantial difference in the sex distribution. CONCLUSIONS: This study provides evidence that work as a nurse may reduce fetal growth and duration of pregnancy. The inference is based on the newborns of teachers as the reference group. However, the prevalence of most of the outcomes was higher among the newborns of all other working women combined than in the newborns of both nurses and teachers.