Risk of preeclampsia and gestational diabetes after occupational exposure to chemicals during pregnancy–A cohort study of births in Sweden 1994–2014

Many women are occupationally active during pregnancy. The aim of this study was to investigate associations between exposure to chemicals during pregnancy and the risk of gestational diabetes or preeclampsia. The cohort included singleton births in Sweden between 1994 and 2014. The cohort was limited to low-educated mothers to reduce potential confounding from unidentified life-style associated factors. Information on occupation (full-time employed) at beginning of pregnancy, demographic data, education, personal risk factors and medical diagnoses were obtained from national records. Occupational exposure to 20 chemicals/particles was assessed by a time-specific job exposure matrix (SweJEM). Relative risks (RR) were adjusted for birth year of the child and mother's age, parity, country of birth, smoking, BMI, and occupational exposure to physical strain, low decision authority, noise, and whole-body vibrations. There were 307,985 births in the cohort. The risk of preeclampsia was elevated after exposure to diesel engine exhaust (RR 1.19; 95 % CI 1.03-1.37), gasoline engine exhaust (RR 1.26; 1.05-1.52) or to carbon monoxide (RR 1.21; 1.03-1.42). Exposure to lead was associated with an elevated risk of gestational diabetes, (RR 2.41; 1.05-5.55), based on six cases only, though. An elevated risk of preeclampsia in association with combustion products is corroborated by studies of traffic-related urban air pollution and of smoke from wildfires. Exposure to motor exhaust during pregnancy should be minimised. Exposure to lead during pregnancy should be avoided also because of serious neurodevelopmental effects for the child.