Seasonal Variation of Nonsyndromic Orofacial Clefts in Northern Chinese Population

Nonsyndromic orofacial clefts (NSOC) comprise a range of disorders affecting the lips and oral cavity. Various authors evaluated seasonal influence on the occurrence of NSOC differently. The aim of present study was to investigate seasonal variation in birth of individuals with orofacial cleft in northern China.

A retrospective study comprised 499 cases and 452 controls were conducted. Children with NSOC operated in The First Affiliated Hospital of Harbin Medical University from 2009 to 2015 were investigated. Controls were children patients with trauma and bone fracture from the same hospital during the same period. Data on sex, birth time, area of residence was retrospectively collected from patients' records. Chi-squared test was used for comparisons. P values less than or equal to 0.05 were considered to be significant.

Seasonal distribution was significantly different between cases and controls (P < 0.05). Birth time peaks of cases, especially males, occurred in winter. Furthermore, compared with controls, more cases with cleft lip/palate were born in winter (P < 0.05). There was no significant seasonal difference between female cases and controls (P > 0.05), and no statistical difference was found between cases with cleft palate and controls (P > 0.05).

Our study revealed the presence of seasonal variation in individuals with orofacial cleft in northern Chinese population. We found a peak incidence of birth time for NSOC during winter.