title: Seasonal impact in the frequency of isolated spina bifida.
abstract: OBJECTIVE
  To evaluate whether a relationship exists between season at conception and occurrence of isolated spina bifida (ISB).
  
  
  METHODS
  All fetuses with prenatal diagnosis of ISB were analyzed according to date of conception. We compared the seasonal rates of conception between ISB fetuses and a control group consisting of a cohort of fetuses delivered during the same period from 1992 to 2009.
  
  
  RESULTS
  In the control group, conceptions were equally distributed among the four seasons. Chi-square analysis showed a significantly higher rate of ISB conceptions in the fall compared with the control group (16/36, 44% vs. 12467/50533, 25%, Odds Ratio (OR) 2.44, 95% confidence interval 1.21-4.92). Not a single woman with a fetus affected by ISB took preconceptional supplement of folic acid.
  
  
  CONCLUSIONS
  Seasonality affects the frequency of ISB. We hypothesize that the seasonal differences may reflect dietary and climate changes with reduced intake of folic acid in the fall.
authors.affiliation: Department of Obstetrics and Gynecology, University of Milano Bicocca, Monza, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Giardini
authors.forename: Francesca Maria
authors.initials: FM
authors.lastname: Russo
authors.forename: Sara
authors.initials: S
authors.lastname: Ornaghi
authors.forename: Lyudmyla
authors.initials: L
authors.lastname: Todyrenchuk
authors.forename: Patrizia
authors.initials: P
authors.lastname: Vergani
mesh_terms: D016022:Case-Control Studies; D005260:Female; D005306:Fertilization / Q000502:physiology*; D006801:Humans; D011247:Pregnancy; D011296:Prenatal Diagnosis; D015995:Prevalence; D012307:Risk Factors; D012621:Seasons; D016135:Spinal Dysraphism / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology*