Background: Seasonality of the incidence of congenital anomalies has provided useful clues in etiological research. However, seasonality of oral-facial clefts is inconsistent in many countries, including native China. The aim of this study was to determine whether births of patients with oral-facial clefts follow a seasonal pattern in a native Chinese population.
Methods: Patients with oral-facial clefts treated at the Plastic Surgery Hospital between January 2002 and December 2011 were retrospectively investigated. The controls comprised all living births from the obstetric department of the Third Affiliated Hospital of Peking University from January 2002 to December 2011. Seasonal variations in birth months were analyzed using the χ test.
Results: A total of 6193 patients with oral-facial clefts and 13,254 healthy living newborns were included in this study. Birth time peaks of the patients occurred in autumn and winter, especially in October and January, compared with the nadir in the summer (P < 0.05). The birth time peaks of male patients occurred in autumn and winter, especially in October, February, and January. The birth time peaks of female patients occurred in autumn and winter, especially in January, October, and November. There was a statistical difference in birth distribution among the different months (P < 0.05) and 4 seasons (P < 0.05) in female patients. No statistical difference was found in male patients (P > 0.05).
Conclusions: There is a possible seasonality in birth months and a difference between sexes of patients with oral-facial clefts in this native Chinese population. This approach could be useful to study the etiology and pathogenesis of oral-facial clefts.