Sex Differences in the Prevalence of Congenital Anomalies: A Population-Based Study

BACKGROUND: Limited data is available concerning the sex distribution of various congenital anomaly subtypes. This study investigated sex differences in the prevalence of congenital anomalies, overall and by subtype, using high quality population-based data from the North of England. METHODS: Information on congenital anomalies occurring among singleton pregnancies during 1985-2003 were extracted from the Northern Congenital Abnormality Survey (NorCAS). Anomalies were categorized by groups, subtypes, and syndromes according to the European Surveillance of Congenital Anomalies guidelines. Relative risks (RRs) comparing the prevalences in males to that in females were calculated for a range of congenital anomaly subtypes. RESULTS: A total of 12,795 eligible cases of congenital anomaly were identified during the study period, including 7019 (54.9%) males and 5776 (45.1%) females. Overall, male fetuses were significantly more prevalent in pregnancies affected by a congenital anomaly than female fetuses (RR, male vs. female 5 1.15; 95% confidence interval [CI], 1.11-1.19), but there was significant heterogeneity between subtypes (p < 0.001). Forty-four of 110 (40%) unique subtypes were at least 40% more prevalent in males than females, with affected subtypes occurring across all major anomaly groups. Thirteen of 110 (12%) unique subtypes were at least 40% more prevalent in females than males, but the female-biased RR of a neural tube defect was less pronounced than previously reported (RR = 0.84; 95% CI, 0.73-0.95). CONCLUSION: This study adds to the growing evidence of sex-specific differences in the prevalence of a wide range of congenital anomaly subtypes. Birth Defects Research (Part A) 91: 894-901, 2011. (C) 2011 Wiley-Liss, Inc.