Relationship between interpregnancy interval and congenital anomalies

Objective To assess the association between interpregnancy intervals and congenital anomalies. Study Design A retrospective cohort study on women who had 2 consecutive singleton births from 1999–2007 was conducted using a linked dataset from the Alberta Perinatal Health Program, the Alberta Congenital Anomalies Surveillance System, and the Alberta Health and Wellness Database. Interpregnancy interval was calculated as the interval between 2 consecutive deliveries minus the gestational age of the second infant. The primary outcome of congenital anomaly was defined using the International Classification of Diseases. Maternal demographic and obstetric characteristics and interpregnancy intervals were included in multivariable logistic regression models for congenital anomalies. Results The study included 46,243 women, and the overall rate of congenital anomalies was 2.2%. Both short and long interpregnancy intervals were associated with congenital anomalies. The lowest rate was for the 12-17 months category (1.9%, reference category), and increased rates were seen for both short intervals (2.5% for 0-5 months; adjusted odds ratio, 1.32; 95% confidence interval, 1.01–1.72) and long intervals (2.3% for 24-35 months; adjusted odds ratio, 1.25; 95% confidence interval, 1.02–1.52). Statistically significant associations were also observed for folate independent anomalies, but not for folate dependent anomalies. Conclusion The risk of congenital anomalies appears to increase with both short and long interpregnancy intervals. This study supports the limited existing studies in the literature, further explores the types of anomalies affected, and has implications for further research and prenatal risk assessment.