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Work schedule and physical factors in relation to fecundity in nurses
  1. Audrey J Gaskins1,2,
  2. Janet W Rich-Edwards2,3,4,
  3. Christina C Lawson5,
  4. Eva S Schernhammer2,3,
  5. Stacey A Missmer2,3,6,
  6. Jorge E Chavarro1,2,3
  1. 1Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
  2. 2Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
  3. 3Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
  4. 4Department of Medicine, Connors Center for Women's Health and Gender Biology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
  5. 5National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Cincinnati, Ohio, USA
  6. 6Department of Obstetrics, Gynecology and Reproductive Biology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
  1. Correspondence to Dr Audrey J Gaskins, Department of Nutrition, Harvard T.H. Chan School of Public Health, Building II 3rd Floor, 655 Huntington Avenue, Boston, MA 02115, USA; ajg219{at}mail.harvard.edu

Abstract

Objectives To evaluate the association of work schedule and physical factors with fecundity.

Methods Women currently employed outside the home and trying to get pregnant (n=1739) in the Nurses’ Health Study 3 cohort (2010–2014) were included in this analysis. Work schedule and physical labour were self-reported on the baseline questionnaire, and every 6 months thereafter the women reported the duration of their ongoing pregnancy attempt. Multivariable accelerated failure time models were used to estimate time ratios (TR) and 95% CIs.

Results Among the 1739 women (median age=33 years, 93% Caucasian) the estimated proportions of women not pregnant after 12 and 24 months were 16% and 5%, respectively. None of the various shift work patterns were associated with duration of pregnancy attempt (as a surrogate for fecundity). However, women working >40 h/week had a 20% (95% CI 7 to 35%) longer median duration of pregnancy attempt compared to women working 21–40 h/week (p-trend=0.005). Women whose work entailed heavy lifting or moving (ie, 25+ pounds) >15 times/day also had a longer median duration of pregnancy attempt (adjusted TR=1.49; 95% CI 1.20 to 1.85) compared to women who never lifted or moved heavy loads (p-trend=0.002). The association between heavy moving and lifting and duration of pregnancy attempt was more pronounced among overweight or obese women (body mass index, BMI<25: TR=1.17; 95% CI 0.88 to 1.56; BMI≥25: TR=2.03, 95% CI 1.48 to 2.79; p-interaction=0.007).

Conclusions Working greater than 40 h per week and greater frequency of lifting or moving a heavy load were associated with reduced fecundity in a cohort of nurses planning pregnancy.

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