Congenital anomalies (birth defects or congenital malformations) are abnormalities that are present at birth, even if not diagnosed until months or years later. They may be present from conception, as is the case with a chromosome defect (e.g. Down syndrome) or gene mutation (e.g. achondroplasia), and they also include those structural defects that occur in the embryonic period up to the end of the seventh week of gestation (e.g. spina bifida) or in the early fetal period between 8 and 16 weeks gestation, (e.g. orofacial clefts).

Congenital anomalies are an important health issue because of their impact on the health and wellbeing of Canadian infants and children and their families and because of the health resources they require for management and treatment. Approximately 1 in 25 Canadian babies is diagnosed with 1 or more congenital anomalies every year. Between 1998 and 2009, the national congenital anomalies prevalence rate decreased from 451 to 385 per 10 000 total births, probably due to 3 factors:

Despite the decrease in the overall prevalence rate, congenital anomalies are second only to immaturity as the leading cause of infant death.