A review of seasonality of cleft births - The Brazil experience.

AIMS: Evaluate the seasonal influence in nonsyndromic cleft lip and/or palate (NSCL/P) in Brazilian patients. METHODS: A case-control study, with 361 unrelated patients with NSCL/P and 481 healthy individuals, was done on a reference service for craniofacial deformities in Minas Gerais State, Brazil. Information was collected from clinical records considering gender, month of birth, as well as with the seasons. RESULTS: Nonparametric tests did not show a seasonal variation in month of birth and in seasons of year of NSCL/P compared to a control group (p = 0.902 and p = 0.679, respectively). A difference in births between the groups was identified only in January, however, was not significant. Moreover, among the control group there were more births in the months of February and August, and for the cleft group, more in July and August. The males were more affected by cleft lip with or without palate (CLP) and the females by isolated cleft palate (CP) manifestation. The ratio of CL:CLP:CP indicated that CLP was predominant when compared with CL and CP, CLP was more frequent in male patients, and CP predominance was seen in females. CONCLUSION: This study did not show seasonal differences in births on NSCL/P in a Brazilian group, emphasizing that environmental factors may be related to oral clefts. These results provide a basis for further epidemiological studies of orofacial clefts in Brazil.