Risk of birth defects in children of mothers with defects

There is evidence that women with congenital anomalies are at risk of having an infant with the same defect. However, the risk of having an infant with a different type of defect is less well described. We evaluated the extent to which offspring of women with congenital anomalies were at risk of having a birth defect, including defects that were similar to or different from their mother's. We analyzed a retrospective cohort of 1,311,532 infants born in Canada between 2006 and 2022. The exposure was a maternal congenital anomaly, and the outcome included birth defects in the newborn. We estimated risk ratios (RR) and confidence intervals (CI) for the association of specific maternal anomalies with the risk of having an infant with a similar or different defect using log-binomial regression models adjusted for patient characteristics. While mothers with anomalies were at risk of having an infant with the same defect, associations with other types of defects were not as strong. For example, compared with no maternal anomaly, maternal urogenital defects were associated with up to 45 times the risk of having an infant with a similar urogenital defect (RR 45.33, 95 % CI 31.92–64.36), but <2 times the risk of having an infant with orofacial clefts (RR 1.89, 95 % CI 1.07–3.34) and clubfoot (RR 1.36, 95 % CI 1.02–1.81). The findings suggest that maternal congenital anomalies are only weakly associated with occurrence of a different type of defect in offspring.