Exposure to pesticides during pregnancy and the risk of neural tube defects: A systematic review

Exposure to pesticides during pregnancy has been associated with several serious congenital malformations, such as neural tube defects, therefore, is a cause for concern in terms of human health. This review aims to gather information related to maternal exposure during pregnancy and the risk of triggering neural tube defects in the offspring. The search strategy for the studies followed the PRISMA guidelines. We conducted a systematic search in the Science Direct, PubMed, Cochrane Library, Embase, Scopus, and Web of Science databases for all epidemiological studies that sought to associate exposure to pesticides during embryonic development with the risk of neural tube defects (NTDs). The keywords used were "pesticide", "herbicide", "congenital" and "neural". Of the 229 articles, 8 eligible ones (7 case-control and 1 cross-sectional) evaluated pesticide exposure in pregnancy. Different methods were used, including analysis of biological samples and questionnaires. The pesticides studied included insecticides, herbicides, fungicides, and nematicides. Insecticides were the most studied, with variations in concentrations between tissues and studies. Distinct levels of pesticides have been detected in maternal serum, placenta, and umbilical cord. Models were statistically adjusted for confounding factors, such as smoking and dietary supplement intakes. Concentrations were measured in different exposure windows (periconception and prenatal), related to NTDs such as anencephaly and spina bifida. Different data collection techniques, types of biological samples, and exposure windows were used, which made comparison difficult. The main pesticides studied included DDT, DDE, HCH, and endosulfan. Maternal serum showed the highest concentrations of pesticides, but detection in placental tissue and umbilical cord confirms embryonic exposure. Confounding variables were adjusted for in the analysis of the articles, but they may still contribute to the risk of NTDs. All the studies analyzed pesticide exposure and the relationship with NTDs. However, a more standardized survey would be ideal for better comparisons.