Seasonal variations in microtia of Chinese population

Background: Seasonality of congenital birth defect could help to identify environmental risk factors. Data concerning the seasonality of the prevalence of microtia are little. This article aims to determine whether births of microtia follow a certain pattern. Methods: Data were obtained from 2669 patients with microtia who were admitted to Second Ear Reconstruction Center of Plastic Surgery Hospital, Chinese Academy of Medical Science from January 2007 to December 2013. The controls consist of all living births from the Obstetric Department of the Haidian Maternal & Child Health Hospital during the same time. Seasonal variations in months of births were analyzed by using x² test. Results: A total of 2669 patients with microtia and 89,273 healthy living newborns were included in this study. Birth time peak of the patients occurred in autumn, especially in November, compared with the nadir in the spring, especially in April (P G 0.05). The birth time peak of male patients occurred in autumn, too, especially in October and November, While the valley occurred in spring (April, too). However, the seasonality in female patients is not so apparent with the peak occurred in the tail of summer and autumn, especially in August, November, and September orderly, while the valley occurred in March. Conclusions: There is a possible seasonality in birth months and a difference between sexes of patients with microtia in this native Chinese population. This approach could be useful to study the etiology of microtia.