work and fertility  Shift work may increase a woman’s risk for fertility and menstrual problems, according to new British research. The study, presented in July 2013 to the European Society of Human Reproduction and Embryology, defines shift work as alternating shifts, evenings, and nights as part of a regular schedule. The researchers looked at all studies on shift work and reproduction published between 1969 and 2013, assessing data gathered from 119,000 women.

Researchers found that women who performed shift work had a 33 percent higher risk for menstrual issues and an 80 percent higher risk for fertility problems. Women who worked only night shifts did not seem to have a statistically higher incidence of fertility or menstrual problems but did have a statistically greater risk for miscarriage; women who worked occasional night shifts as part of shift work did not have a greater risk for miscarriage.

One possible explanation is that shift works disrupts a woman’s circadian rhythm, which is her body’s natural 24-hour cycle. Chronic interference with this circadian rhythm can cause problems with the human body’s “clock genes” in a way that throws off many biological functions, including reproduction.

Another explanation is that the stress of shift work has a negative effect on fertility and pregnancy. Stress can cause fluctuations in hormone production levels, possibly contributing to menstrual irregularities, poor reproductive outcomes, infertility and low birth weights.

The study builds on previous research that suggests that shift work can have harmful effects late in pregnancy. Some researchers think shift work and the sleep deprivation it causes contributes to heart risk, stress, unhealthy behaviors such as smoking and alcohol consumption, and metabolic changes including high blood pressure and high cholesterol.

Medical experts suggest pregnant women and women trying to get pregnant work regular hours; those women who must perform shift work should pay close attention to warning signs of reproductive problems, including menstrual irregularities. Additionally, women should see their doctors, cut back on coffee and alcohol, and consult with a reproductive specialist to increase her odds for becoming pregnant.

Source: Priedt, Robert. "Shift Work Might Affect Women's Periods, Fertility: Study." MedlinePlus. U.S. National Library of Medicine. 10 Jul 2013. Web. 13 Sept 2013.