Shift work and reproductive health.

Nonstandard workhours may disturb normal body functions, but their relation to reproductive outcome is poorly understood. Two newly published studies suggest an association between rotating shift work and prolonged waiting time to pregnancy. Seven of nine studies on spontaneous abortion suggest that some forms of shift work may be associated with increased risk. Four studies indicate that shift work including night schedules may be related to preterm birth. Moreover, some results have related rotating schedules to intrauterine growth retardation. In the published studies, the type of work schedule examined has varied, and the applied definition of shift work has not necessarily been clear. The main interest areas, however, have been work involving evening and night shifts, rotating or changing schedules, and the irregularity of work patterns. Although the evidence is not ample and remains ambiguous, it is prudent to consider shift work as a potential risk to reproduction.