Seasonal Variation of Orofacial Clefts

Orofacial clefts represent the most common craniofacial malformation diagnosed at birth and may be divided into isolated cleft lip (CL), cleft lip and palate (CL/P), or isolated cleft palate (CP). The causes of orofacial clefts have long been understood to be multifactorial; however, research into the genetic and environmental factors underpinning these disorders in African populations is scant. Seasonal variation in the occurrence of orofacial clefts was investigated. Seasonal variation is defined as differences due to periodic, temporal, and external influences, namely the particular time or season of the year.

The study design is a retrospective record review and sampled patients presenting to the Cleft Clinic at Charlotte Maxeke Johannesburg Academic Hospital during the time period October 2000 to October 2015. Ethical approval was obtained. Information recorded included patient demographics (date of birth and gender), diagnosis and laterality of the cleft.

This study includes 512 infants. This study shows seasonal variation in the incidence of orofacial clefts limited to patients with both a CL/P. There was no significant seasonal variation observed in isolated CL or CP and laterality of the cleft. Significant seasonal variation was observed only in those born in winter versus summer, with more children born with a CL/P in winter months.

Seasonal (or temporal) variation indicates a distinct environmental influence on the formation of orofacial clefts in utero, more specifically in pregnancies with the first trimester during spring. Several reasons have been advanced and include sunlight exposure and vitamin D levels, weight gain, and maternal obesity. More study is required to further elucidate these reasons.