As per a new study, women – especially those who are overweight or older – whose jobs require them to move or lift heavy loads could be putting their fertility at risk. The study’s results showed that women who worked at places that involved lifting weights had 8.8 percent fewer total eggs and 14.1 percent fewer mature eggs compared with women who reported never lifting or moving heavy objects at work. There was a further dip in the fertility of those women, who worked at night or on rotating shifts. “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-Alarcon, research fellow at Harvard TH Chan School of Public Health. Among women who were overweight or obese and those aged 37 or older, the association between heavy lifting and mature egg yield was in the reverse. Although previous studies have suggested a link between work schedule, physical factors on the job and the biologic capacity for reproduction, Audrey Gaskins, research associate at Harvard TH Chan School of Public Health, said, “Our study is the first which shows that occupational heavy lifting and non-day shifts may be adversely affecting egg production and quality, rather than accelerating ovarian ageing.” For the new study, published in the journal Occupational & Environmental Medicine, the team analysed nearly 500 women seeking infertility treatment at Massachusetts General Hospital in the US, from 2004-2015. However, the mechanism by which moving or lifting heavy loads could affect egg quality is still unknown. As for how working non-day shifts may affect egg yields, it is speculated that it may have to do with circadian rhythm disruption, the researchers said.