Women who work fixed nighttime hours during pregnancy are more likely to suffer fetal loss, according to a new study. However, this correlation was not found among women who work rotating shifts.
Researchers at the Danish Epidemiology Research Center analyzed data on more than 42,000 Danish women who worked during pregnancy. They compared rates of pregnancy loss of women who worked daytime hours to women who worked other shifts. Of the 42,000 women, 34,000 worked daytime hours only, 400 worked nighttime hours only, and 3,300 worked rotating shifts.
Of all the pregnancies, 1.5 percent ended in fetal loss. Risk for fetal loss did not increase for women who worked daytime hours or for those who worked rotating shifts. However, women who worked fixed night hours had an 85-percent higher risk of late fetal loss than daytime workers. Fetal losses included late spontaneous abortion and stillbirth.
Reasons for this increased risk are unknown, but researchers speculate higher estrogen levels related to night work might play a role.
The study also examined the effects of job stress, which has been linked to certain health problems. Although shift workers typically have more stressful jobs, stress was not a risk factor for fetal loss
SOURCE:Journal of Occupational and Environmental Medicine, 2004;46:1144-1149
