Impact of maternal exposure to pyrethroid pesticides across pregnancy on leptin in cord blood of pregnant women in rural areas

Background Leptin can affect early-stage weight gain in infants, and pyrethroid pesticide exposure during pregnancy can affect birth weight in newborns.

Objective This study aims to investigate the impact of maternal non-occupational exposure to pyrethroid pesticides during whole pregnancy on fetal cord blood leptin levels.

Methods A total of 566 mother-infant pairs were included into current study from a prospective birth cohort in rural Xuanwei, Yunnan, China from January 2015 to July 2018. In each trimester of pregnancy the participated women were asked to complete a questionnaire survey and their urine samples were collected, and the cord blood samples of newborns were also collected after delivery. Pyrethroid metabolites such as 3-phenoxybenzoic acid (3-PBA), 4-fluoro-3-phenoxybenzoic acid (4-F-3-PBA), and (2, 2-dibromovinyl)-2, 2-dimethyl-cyclopropane-1-carboxylicacid (DBCA) in urine samples were measured by high performance liquid chromatography-tandem mass spectrometry. Leptin in cord blood samples was tested by ELISA. Based on the levels of 3-PBA, 4-F-3-PBA, and DBCA, the study subjects were divided into undetected group (< LOD), low exposure group (LOD-P₅₀ of detected level), and high exposure group (>P₅₀ of detected level); based on the detection state of pyrethroid metabolites in urine samples of three pregnant stages, the study subjects were divided into three groups:negative during pregnancy; positive in any one trimester; positive in any two trimesters; positive in all trimesters. Multiple linear regression analysis was used to explore the impacts of exposure levels of pyrethroid metabolites during pregnancy on leptin in cord blood.

Results During whole pregnancy, the 3-PBA, DBCA, and 4-F-3-PBA median concentrations were 0.413-0.459, 0.964-1.431, and 0.310-0.394 μg·g^-1 (in creatinine), respectively, and the leptin median concentration was 3.936 μg·L^-1. DBCA exposure level in the third trimesterb (95%CI)=0.006 (0.001-0.010) was positively correlated with leptin concentration. BDCA low exposure level (b=0.104, 95%CI:0.015-0.194, P=0.023) and high exposure level (b=0.136, 95%CI:0.005-0.266, P=0.042) in the first trimester were positively correlated with leptin concentration. 4-F-3-PBA low exposure level in the second trimester (b=0.084, 95%CI:0.001-0.167, P=0.048) and high exposure level in the first (b=0.078, 95%CI:0.006-0.150, P=0.034), second (b=0.114, 95%CI:0.030-0.198, P=0.008), and third (b=0.092, 95%CI:0.003-0.181, P=0.043) trimesters were positively correlated with leptin concentration. The levels of 4-F-3-PBA in the groups with positive pyrethroid metabolites in any one trimester, any two trimesters, and three trimesters were positively correlated with leptin concentration (b=0.108, 95%CI:0.028-0.189, P=0.008; b=0.096, 95%CI:0.007-0.185, P=0.035; b=0.164, 95%CI:0.051-0.277, P=0.004).

Conclusion Prenatal pyrethroid pesticide exposure among mothers in rural areas may increase the leptin levels in cord blood of fetuses.