Impact of pre-pregnancy diabetes mellitus on congenital anomalies, Canada, 2002–2012

Abstract

Objective: To examine the impact of pre-pregnancy diabetes mellitus (DM) on the population birth prevalence of congenital anomalies in Canada. Methods: We carried out a population-based study of all women who delivered in Canadian hospitals (except those in the province of Quebec) between April 2002 and March 2013 and their live-born infants with a birth weight of 500 grams or more and/or a gestational age of 22 weeks or more. Pre-pregnancy type 1 or type 2 DM was identified using ICD-10 diagnostic codes. The association between DM and all congenital anomalies as well as specific congenital anomaly categories was estimated using adjusted odds ratios; the impact was calculated as a population attributable risk percent (PAR%). Results: There were 118 892 infants with a congenital anomaly among 2 839 680 live births (41.9 per 1000). While the prevalence of any congenital anomaly declined from 50.7 per 1000 live births in 2002/03 to 41.5 per 1000 in 2012/13, the corresponding PAR% for a congenital anomaly related to pre-pregnancy DM rose from 0.6% (95% confidence interval [CI]: 0.4–0.8) to 1.2% (95% CI: 0.9–1.4). Specifically, the PAR% for congenital cardiovascular defects increased from 2.3% (95% CI: 1.7–2.9) to 4.2% (95% CI: 3.5–4.9) and for gastrointestinal defects from 0.8% (95% CI: 0.2–1.9) to 1.4% (95% CI: 0.7–2.6) over the study period. Conclusion: Although there has been a relative decline in the prevalence of congenital anomalies in Canada, the proportion of congenital anomalies due to maternal prepregnancy DM has increased. Enhancement of preconception care initiatives for women with DM is recommended.

Keywords

• diabetes mellitus, pre-pregnancy, congenital anomaly, birth defect, trends, population attributable risk percent