Night work and the reproductive health of women: an integrated literature review.

Introduction: The aim of this review was to synthesize current evidence on the effects of night work on the major stages of women's reproductive health, specifically the menstrual cycle, fertility, pregnancy, and menopause. Current understanding suggests that night work (work that causes disruption of a worker's circadian [day/night] rhythms) adversely affects workers' health and well-being. A complex relationship exists between circadian rhythms and reproductive hormones, and this may potentially increase the vulnerability of women to the detrimental effect of night work, including during menopause.

Methods: A systematic search was conducted (March-May 2011) via CINAHL, MEDLINE, Sociological Abstracts, and Business Source Premier for primary research studies written in English using the key words "shift-work" and "female/women." Findings of identified articles were themed to pregnancy, fertility, aspects of menstrual cycles, and menopause.

Results: Twenty articles were identified, (13 articles concerning pregnancy, 3 addressing fertility, and 4 addressing aspects of the menstrual cycle) but no studies addressing menopause were located. All identified articles demonstrated problematic approaches to the determination of night-work exposure.

Discussion: Evidence of the impact of night work on female reproductive health as presented in the current literature is inconclusive. Moreover, available evidence needs to be interpreted with caution, given the various limitations and inconsistencies among the studies in the measurement of night-work exposure and shift-work patterns. Studies that focus specifically on night work are needed to facilitate an understanding of the impact of circadian disruption on the reproductive health of women undertaking night work.