Dissertations & Theses (Open Access)

Date of Award

8-2020

Degree Name

Master of Science (MS)

Advisor(s)

A.J. Agopian

Second Advisor

Michael Swartz

Abstract

Although orofacial clefts, which include cleft palate alone (CP) and cleft lip with or without cleft palate (CL±P), are among the most common birth defects, their etiology is complex and is generally not well understood. While some clefts are caused by rare syndromes, the majority occur in the absence of a syndrome, either in association with co-occurring defects or as isolated defects. Among these non-syndromic cases, epidemiologic studies have identified demographic variables that are associated with CP and/or CL±P, such as geographic location and infant sex, as well as several maternal characteristics, though some of these associations have been weak and/or inconsistent. In the United States, the majority of population-based studies that have explored the association between infant and maternal characteristics and the prevalence of CP and CL±P were conducted over a decade ago and likely did not have the statistical power to examine small subgroups. In particular, one descriptive study of non-syndromic CP and CL±P in Texas examined data from 1995 to 1999 and included 896 infants. We sought to update this work. In addition, while previous population-based studies have examined the epidemiology of non-syndromic clefts separately for infants with CP and with CL±P, we are unaware of studies that have accounted for potential differences between clefts that occur as isolated and those with additional defects, though there are likely epidemiologic differences between them. The main objective of this study was therefore to describe the current epidemiology of non-syndromic CP and CL±P in Texas (1999-2014 deliveries), examining differences in the characteristics of infants with CP and CL±P based on the presence/absence of additional defects. The analysis used data from the Texas Birth Defects Registry (TBDR) for 1,815 infants with CP and 5,066 with CL±P, without a syndrome diagnosis. Poisson regression was used to calculate crude and adjusted prevalence ratios for each characteristic, separately for each cleft sub-phenotype. Several sociodemographic and maternal characteristics were associated with the prevalence of CP and CL±P, the most significant being infant sex and maternal race/ethnicity, age, smoking, and diabetes. In addition, there were several differences in the characteristics of infants with isolated versus non-isolated clefts. For example, maternal prepregnancy diabetes was associated with an increased prevalence of CP and CL±P, but only when additional defects were present. Overall, findings from this study provide a contemporary description of the distribution of orofacial clefts in Texas and may contribute to increasing our understanding of the etiology of CP and CL±P.

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