Epidemiologic characteristics of anophthalmia and bilateral microphthalmia among 2.5 million births in California, 1989-1997.

There is a paucity of epidemiologic information about the eye malformations anophthalmia and microphthalmia. Using data from a large population-based registry, we explored prevalences and maternal/infant characteristics associated with anophthalmia and bilateral microphthalmia. Data were derived from the California Birth Defects Monitoring Program, a population-based active surveillance system for collecting information on infants and fetuses with congenital malformations using multiple source ascertainment. Approximately 2.5 million births (liveborn and stillborn) occurred during the ascertainment period, 1989-1997. Information on maternal and infant/fetal characteristics was obtained from California birth certificate and fetal death files. The prevalence per 10,000 livebirths and stillbirths for anophthalmia was 0.18 and for bilateral microphthalmia was 0.22. These estimates reflect prevalences among births without chromosomal anomalies. Relative risks of anophthalmia were modestly higher among women aged 40 or more (relative risk = 2.0, 95% confidence interval 0.5-8.6). Risks were substantially lower for those mothers with >12 years of education, even after adjusting for other study factors, relative risk = 0.6 (0.2-1.7). The risk of anophthalmia was approximately twofold among multiple births compared to singletons. Similar to results for anophthalmia, decreased risks for bilateral microphthalmia were observed for maternal education of 12 years or more and increased risks observed for multiple births. These data show descriptive epidemiologic features of anophthalmia and bilateral microphthalmia.