INTRODUCTION: Anorectal malformations are birth defects that affect 1 in 5000 live births. Despite the research, the cause is still unknown, but genetic and environmental factors have been described to contribute to its pathogenesis. We report the case of a child with an anterior ectopic anus in which prenatal environmental factors were systematically assessed using a screening evaluation interview, the Green Page, and a complete Pediatric Environmental History. CASE: A first born of a 29 year old woman with a history of epilepsy treated with high doses of lamotrigine, levetiracetam, and clobazam, and a subclinical hypothyroidism treated with levothyroxine. Periconceptional supplementation with 400mcg of folic acid, maternal and paternal smoking habit, and some occupational exposures to chemical hazards. No personal or family history of congenital malformations. DISCUSSION: Some previously related environmental factors were found, such as mother's epilepsy, high lamotrigine dose, tobacco exposure, air pollution, and in a lesser risk the use of levothyroxine. The Green Page and the Pediatric Environmental History could contribute to identifying and reducing environmental risks related to birth defects.