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Your Environment. Your Health.

Physically Demanding or Night-shift Work Linked to Markers of Fertility

Russ Hauser, M.D., Sc.D.
Harvard School of Public Health
R01ES022955, R01ES009718, P30ES000002

Lifting heavy loads at work and working non-daytime schedules might be linked to decreased fertility, according to a new study by NIEHS grantees. The researchers reported that these occupational factors were associated with fewer mature eggs and fewer total eggs in the ovaries of study participants. Fewer eggs could lead to decreased fertility.

The researchers studied nearly 500 women seeking infertility treatment at Massachusetts General Hospital from 2004 to 2015. Markers of fertility were measured, including hormone levels, numbers of mature eggs capable of developing into healthy embryos, and structures in the ovary that indicated the number of immature eggs. The team analyzed associations between these markers and what the women reported on a questionnaire about their job demands and schedules.

Overall, women who reported moving or lifting heavy loads at work averaged 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. Non-daytime schedules, including working at night or rotating shifts, were also associated with fewer eggs. The association between heavy lifting and decreased mature egg yield was even stronger among women who were overweight or obese, and those aged 37 years or older.

Although previous studies demonstrated a link between work schedule and physical factors and fertility, none were able to directly measure biological markers of fertility, such as reproductive hormones or ovarian function. Markers associated with egg yields did show an association with occupational factors, but hormone levels did not, suggesting that lower eggs yields might be an important factor that affects the relationship between physically demanding or night-shift work and fertility.

Citation: Mínguez-Alarcon L, Souter I, Williams PL, Ford JB, Hauser R, Chavarro JE, Gaskins AJ; Earth Study Team. 2017. Occupational factors and markers of ovarian reserve and response among women at a fertility centre. Occup Environ Med; doi:10.1136/oemed-2016-103953

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