Aims: To evaluate the association between parental occupational exposure to agricultural work and the risk of anencephaly in three Mexican states.
Methods: A paired case control study (1:1) was done based on records of the Epidemiological Surveillance System of Neural Tube Defects in Mexico; 151 cases of anencephaly of more than 20 weeks' gestation were selected between March 2000 and February 2001. Controls were selected from the same maternity services as those of the cases and were born alive without congenital malformations. Information was obtained from both parents by means of a general questionnaire, a food frequency questionnaire, and a specific questionnaire on occupational exposure to pesticides. Exposures were analysed with emphasis on the three months before and one month after the last menstruation periods (acute risk period (ARP)), as well as exposure prior to the above mentioned period (non-acute risk period (NARP)).
Results: The children of mothers who worked in agriculture in the ARP had a greater risk of anencephaly (OR = 4.57, 95% CI 1.05 to 19.96). The risk of fathers having a child with anencephaly was greater in those who applied pesticides irrespective of whether it was done in the ARP or the NARP (OR = 2.50, 95% CI 0.73 to 8.64; and OR = 2.03, 95% CI 0.58 to 7.08, respectively).
Conclusions: These results support the hypothesis of the effect of maternal exposure to agricultural work on anencephaly and suggest that exposure of the father to pesticides in the periconceptional period or prior to this can also increase the risk of having an anencephalic child.