1. GaoGLivingstonGPew Research Center2018-04-06Working while pregnant is much more common than it used to be
http://www.pewresearch.org/fact-tank/2015/03/31/working-while-pregnant-is-much-more-common-than-it-used-to-be/
2. Central Statistics Office, the Netherlands2017-11-30[Labor participation by age and gender]
https://www.cbs.nl/nl-nl/achtergrond/2017/07/arbeidsparticipatie-naar-leeftijd-en-geslacht
3. Miscarriage and occupational activity: a systematic review and meta-analysis regarding shift work, working hours, lifting, standing, and physical workload
4. First-Trimester Working Conditions and Birthweight: A Prospective Cohort Study
5. Physically demanding work and preterm delivery: a systematic review and meta-analysis