title: Seasonal and yearly trends in cleft lip and palate in northeast Iran, 1989-2011.
abstract: Cleft lip and palate are the most common craniofacial congenital anomalies. The aim of this study was to detect the trend of seasonal and yearly fluctuations in the prevalence of cleft lip and palate birth in the northeast of Iran.
  
  
  METHODS
  Data were obtained from 348 patients referred to the Cleft Lip and Palate Research Center of Mashhad Dental School during a 22-year period. Children with syndromes or patients from other areas of Iran were not included in this investigation. Recorded data included sex, type of cleft, date of birth, place of birth, and area of residence. Chi-squared test was used for comparisons.
  
  
  RESULTS
  Without sex difference, the prevalence of all cleft types was more in winter and spring; however, there was no significant seasonal difference in birth dates of children with clefts (P = 0.777). This study showed that there was no significant difference in cleft types in both sexes(P = 0.113). Moreover, there appeared to be a reduction over time in the prevalence of all types of clefts, but there were fluctuations between years.
  
  
  CONCLUSIONS
  This article suggests the influence of genetic and environmental factors other than season on the prevalence of orofacial clefts.
authors.affiliation: Department of Orthodontics, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Arezoo
authors.initials: A
authors.lastname: Jahanbin
authors.forename: Neda
authors.initials: N
authors.lastname: Eslami
mesh_terms: D016009:Chi-Square Distribution; D002971:Cleft Lip / Q000453:epidemiology* / Q000235:genetics; D002972:Cleft Palate / Q000453:epidemiology* / Q000235:genetics; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007492:Iran / Q000453:epidemiology; D008297:Male; D015995:Prevalence; D012307:Risk Factors; D012621:Seasons