Epidemiologic features of male genital malformations and subtypes in Texas

Although distinct categories of male genital malformations share some common risk factors, few studies have systematically compared epidemiologic features across phenotypes. We evaluated the relationship between several maternal and infant characteristics and five categories of male genital malformations: second- or third-degree hypospadias, hypospadias (regardless of degree), small penis, cryptorchidism, and any male genital malformation. Data for 16,813 cases with isolated male genital malformations and 1,945,841 male live births delivered from 1999 to 2008 were obtained from the Texas Birth Defects Registry. For each phenotype category, 13 maternal and infant variables were assessed, and adjusted prevalence ratios were estimated based on the same multivariable Poisson regression model. A significant negative association was observed between previous live births versus no previous live births and four phenotypes (e.g., adjusted prevalence ratio [aPR] for any male genital malformation: 0.78, 95% confidence interval [CI]: 0.75-0.81). The prevalence of 4 of the phenotypes was significantly higher among multiple versus singleton pregnancies (e.g., aPR for any male genital malformation: 1.35, 95% CI: 1.25-1.47). We also observed significant associations between multiple phenotypes and residential region at delivery, delivery year, month of conception, and maternal age, race/ethnicity, education, and birthplace, including significant associations for trends (maternal age, maternal education, and birth year modeled ordinally). Our results allow for comparison of characteristics across phenotypes and suggest that there may be some common risk factors for multiple male genital malformations (e.g., characteristics related to maternal estrogen levels), while other risk factors may be unique to specific defects.