Women who work irregular shifts suffer more disrupted menstrual cycles, miscarriages and reduced fertility, according to an analysis of data from previous studies presented at a scientific meeting in London.
Irregular hours are associated with a 33 percent greater rate of menstrual disruption and an 80 percent higher rate of subfertility than working regular hours, according to the report to the European Society of Human Reproduction and Embryology today. Those who worked only nights had more miscarriages but didn’t face an increased risk of menstrual disruption or difficulty conceiving.
“If our results are confirmed by other studies, there may be implications for shift workers and their reproduction plans,” one of the study authors, Linden Stocker, a clinical research fellow and obstetrics and gynecology registrar at the University of Southampton, said in a statement.
The findings are based on pooled data from all studies published on the subject from 1969 until January 2013. The studies collectively looked at a total of 119,345 women.
The analysis showed an association between shift work and negative outcomes such as miscarriages; it doesn’t prove that shift work causes the negative outcomes, Stocker said. Disruption of the circadian rhythms that affect the biological function of “clock genes” may explain the link between shift work and reproductive outcomes, she said.
The results should be interpreted cautiously, said Stuart Lavery, a consultant gynecologist at Hammersmith and Queen Charlotte’s Hospitals and director of IVF Hammersmith in London.
“We can’t make any terribly firm conclusions from this study,” Lavery said at a press conference in London. “In attendance are several confounding factors.”