title: Maternal folate exposure in pregnancy and childhood asthma  and allergy: a systematic review.
abstract: Adequate folate status in early pregnancy is critical to prevent congenital malformations, yet little is known about whether exposure to folate, specifically folic acid supplementation beyond the recommended dose, influences chronic health outcomes. The link between maternal folate levels and risk of childhood asthma and allergic disease has been investigated in 10 large prospective cohort studies that reported conflicting results. While the majority of studies reported no association, those supporting a positive relationship found a small increase in risk that was generally transient in nature, confined to early childhood, and associated with folic acid supplementation in late pregnancy. This systematic review presents background information on maternal folate exposure and childhood asthma, synthesizes the current epidemiologic evidence in the context of the methodological differences among studies and their potential limitations, and offers direction for future research.
authors.forename: Susan B
authors.initials: SB
authors.lastname: Brown
authors.forename: Katherine W
authors.initials: KW
authors.lastname: Reeves
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Bertone-Johnson
mesh_terms: D001249:Asthma / Q000139:chemically induced / Q000453:epidemiology*; D019587:Dietary Supplements; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage* / Q000009:adverse effects*; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology*; D018811:Maternal Exposure; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011446:Prospective Studies; D014803:Vitamin B Complex / Q000008:administration & dosage / Q000009:adverse effects
chemical_list: D014803:Vitamin B Complex; D005492:Folic Acid