[Risk factors associated with neural tube defects: exposure during the first trimester of gestation].

The neural tube defects (NTD) are a group of malformations of multifactorial etiology. Their high incidence in Mexico and the etiologic heterogeneity observed in several studies, prompted the present investigation with the main objective of looking for risk factors associated to NTD. We analyzed maternal exposure during the first trimester of pregnancy to different environmental factors, such as acute or chronic illnesses, immunizations, smoking, alcoholism, maternal or paternal occupation and exposure to chemicals. The sample include 360 patients with anencephaly, 249 with spina bifida and 44 with encephalocele, ascertained from a total of 230 635 live births and 4,020 stillborns, studied in the Mexican program of Registro y Vigilancia Epidemiológica de Malformaciones Congénitas Externa. Of the risk factors considered, significant differences with the control group were found for anencephaly in relation to maternal viral upper respiratory infection, hyperthermia, ingestion of analgesics, antiemetics and paternal occupation. In the case of spina bifida, significant differences were found only for viral upper respiratory infections.