Prenatal exposure to insecticides and child weight trajectories in a South African birth cohort

Abstract

Background: DDT or pyrethroid insecticides are sprayed inside dwellings as part of global malaria vector control programs, resulting in high levels of exposure to millions of people, including pregnant women. These chemicals are endocrine disruptors and may affect child growth. Study Design: The Venda Health Examination of Mothers, Babies and their Environment (VHEMBE) is a birth cohort study based in Limpopo, South Africa (n=752). Maternal peripartum concentrations of DDT and its breakdown product DDE were measured in serum and pyrethroid metabolites were measured in urine. Child weight was measured at birth and at 1, 2, 3.5 and 5-year follow-up visits; weight measurements were also abstracted from medical records. Methods: We modelled child weight trajectories using SuperImposition, Translation and Rotation (SITAR) to estimate child-specific weight over time and age at peak weight velocity (APWV). We then estimated associations between insecticides and SITAR parameters using multivariable linear regression. We also investigated whether child sex and maternal energy intake sufficiency during pregnancy modified these associations. Results: Maternal p,p’-DDT was associated with greater weight among girls (β=14g per 10-fold increase; 95%CI=0, 28) and children of mothers with sufficient energy intake (β=18g per 10-fold increase; 95%CI=1, 35). We also found that pyrethroids may be associated with lower weight and earlier APWV among boys, particularly for cis-DBCA, which is specific to deltamethrin (βweight= -24g per 10-fold increase; 95%CI=-52, 4; βAPWV=-2.6 days per 10-fold increase; 95% CI: -5.3, 0.1). Conclusions: Maternal DDT and pyrethroid exposure may be associated with child growth through age 5. Positive associations between p,p’-DDT and weight among girls are consistent with its estrogenic properties, and inverse associations between pyrethroids and weight and APWV among boys may be related to their androgenic properties. These findings, as well as that of effect modification by maternal energy intake, support our previous research in this population.