Millions of women in the United States are shift workers, following schedules that are beyond the typical 9 to 5, but little is known about how their hours can affect their reproductive health and fertility.
Now, a surprising new review of previous studies suggest that shift work can take a serious toll.
According to a study presented at the annual meeting of the European society of human reproduction and Embryology in London this week, women who work irregular shifts are more likely to experience reduced fertility and increased menstrual disturbance. Women who work nights may specifically have an increased risk of miscarriage.
"Nobody who works shifts has changes in biological function, and could be one of a number of things which has an impact on the ability of women to play," Dr. Linden Stocker, researcher at the University of Southampton in the United Kingdom, told The Huffington Post.
Stocker and colleagues reviewed 14 published studies between 1969 and 2013 that investigates the links between shifts and spontaneous abortions, menstrual disorders (defined as cycles of less than 24 days and cycles of 32 or more days) and not get pregnant after a year of trying of. All together, the studies included nearly 120,000 women.
Irregular schedule - Stocker defined as anything out of 8 to 18 - was linked to an increased rate of 33 per cent of menstrual disorders and one rate higher than 80 percent of Subfertility.
Working nights was not particularly tied to menstrual problems or problems getting pregnant, but was linked to an increased risk of miscarriage.
The researchers described the results as the novel, but warned that it should not be oversold. "We have not shown causality; We have found an association, warned the Stocker.
The women who work irregular shifts or nights can participate in any number of behaviors that could be influencing reproductive outcomes. For example, working hours is often linked to loss of sleep, decrease of exercise and poor diet.
But a growing body of research suggests that the physiological changes that accompany the work shift may be the culprits and that reproductive problems are a direct result of interrupted circadian rhythms.
In a preliminary study published last year, researchers manipulated the patterns of light and dark mice were exposed to it to test what effect, if any, this would have on their fertility. A group of mice subjected to repeated changes in its cycle of light / darkness had a success rate of pregnancy of just 22 per cent, compared to a success rate of 90 percent among a group of mice exposed to a typical day/night pattern.
"We were surprised, dramatically, the effect of manipulating the cycle was light-dark," said Keith Summa, researcher at Northwestern University and author in that study, in a statement. "We expected a negative effect of the disruption of the circadian clock, but not both."
Some estimates suggest that up to 15 million Americans take turns regular, including more and more women. According to the work of Sloan and research network of the family at Boston College, nearly one-third of companies with extended hours reported an increase in the number of workers by turns female in a 2004 study. Doctors and nurses often work irregular hours, as pilots, police officers, firefighters, employees of the restaurant and retail and home health aides.
Stocker said that women who work in shifts should not emphasize on the new findings, particularly until future studies have replicated the results.
"We know that many things can help improve reproductive outcomes - a balanced diet, exercise and take care of yourself in general," said. "While we hope that future studies prove or disprove our conclusions, it is important that women are focused on your health in general."
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