PhotoWorking late at night can be a daunting task, and there aren’t many out there who relish heavy lifting and manual labor. Now a new study shows that women who want to have children should avoid both.

Researchers from the Harvard T.H. Chan School of Public Health have found that women who lift heavy loads or work non-daytime work schedules are at risk of decreased fertility.

“Our study suggests that women who are planning pregnancy should be cognizant of the potential negative impacts that non-day shift and heavy lifting could have on their reproductive health,” said lead author Lidia Minguez-Alarcón.

Work and fertility

To come to their conclusions, the researchers studied approximately 500 women who sought out infertility treatment at Massachusetts General Hospital between 2004 and 2015. Due to similar natures, each subject was able to be analyzed by biomarkers related to fertility that are normally unmeasurable in women who can conceive naturally.

After collecting the data, Minguez-Alarcón and her colleagues evaluated the associations between the biomarkers and the physical demands and schedules of each woman’s job. They found that, on average, women who moved or lifted heavy loads at work had 8.8% fewer eggs and 14.1% fewer mature eggs compared to women who did not lift heavy objects, indicating that the activity negatively affected fertility.

Additionally, the researchers found that women had fewer eggs if they worked at night or had a rotating schedule.

Solving the problem

While the researchers aren’t sure what the exact cause is behind the relationship, they found that women who were obese or over the age of 37 were much more likely to have fewer eggs if they lifted heavy loads. However, they have speculated that working non-day shifts could negatively affect egg production because of disruptions to circadian rhythm.

While the study does corroborate some findings from past studies, it is the first to concretely tie egg production and quality to working conditions rather than ovarian age. The researchers hope that their findings will lead to future solutions to the problem.

“Future work. . . is needed to determine whether egg production and quality can be improved, and if so, how quickly, if these exposures are avoided,” said research associate Audrey Gaskins.

The full study has been published in Occupational and Environmental Medicine.

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