First trimester urine glyphosate concentrations and gestational diabetes in nulliparas: a nested case-control study

Abstract

Background: Environmental exposures, such as pesticides, during pregnancy have been associated with several adverse pregnancy outcomes, including miscarriage and shorter gestational length at birth. However, their relationship with gestational diabetes (GDM) is uncertain. The objective of this study was to analyze first-trimester urinary herbicide concentrations for their associations with GDM. Methods: This was a nested case-control study analysis of the Nulliparous Pregnancy Outcomes Study- Monitoring Mothers-to-be (nuMoM2b) study. The study included participants at the three midwestern study sites. We analyzed individuals according to whether they developed GDM. Urinary herbicide concentration at the upper quartile was the exposure of interest. To assess the association of first-trimester urine glyphosate and metabolites with GDM, conditional logistic regression was used for matched pairs models. To test whether the association of herbicides with GDM was modified by BMI, an interaction term of herbicide (dichotomous variable) * BMI was included. Results: The 118 cases of nuMoM2b participants with GDM were matched with 118 randomly selected age-matched controls who had no adverse pregnancy outcomes. Participants with GDM were less likely to be Non-Hispanic White (26.3% vs. 40.7%; p = 0.02), had a higher mean BMI (30.7 ± 8.3 vs. 26.1 ± 6.3; p < 0.01), and were less likely to have graduated from college (55.1% vs. 72.0%; p = 0.007). Glyphosate concentrations were above the limit of detection (LOD) in 93.6% of analyzable samples. In the adjusted conditional logistic regression for the matched pairs model, participants with glyphosate in the upper quartile had significantly higher odds of having GDM (odds ratio [OR] 3.27, 95% confidence interval [CI] 1.04-10.3), with the OR of 1.23 (95% CI 1.02-1.47) for the interaction with BMI. Compared to participants with BMI < 25 kg/m2, the adjusted odds of GDM for participants with obese BMI (≥ 30 kg/m2) was elevated (OR 8.52, 95% CI 1.27-57.2). Conclusion: First trimester urinary glyphosate concentrations were associated with development of GDM, and the magnitude of this association increased at higher BMI.