Case-control study of congenital anomalies in children of cancer patients.

OBJECTIVES To determine whether the offspring of cancer survivors are at an increased risk of congenital anomalies and whether cancer therapy before conception is associated with such an increase. DESIGN Case-control study using computerised record linkage. SETTING Ontario, Canada. SUBJECTS Parents of children born during April 1979 to December 1986 who had a congenital anomaly diagnosed within the first year of life (45,200 mothers and 41,158 fathers) and a matched sample of parents whose children did not have a congenital anomaly (45,200 mothers and 41,158 fathers). MAIN OUTCOME MEASURES Cancer diagnosed in either parent before conception and radiotherapy to the pelvis or abdomen or chemotherapy with an alkylating agent. RESULTS Among the mothers, 54 cases and 52 controls were identified as having had cancer diagnosed in Ontario (relative risk = 1.04, 95% confidence interval 0.7 to 1.5) and among the fathers, 61 cases and 65 controls were identified (0.9, 0.7 to 1.4). No significant associations were found between congenital anomalies in the offspring and any type of cancer treatment in either the mothers or the fathers. CONCLUSIONS The risk of congenital anomalies among liveborn offspring whose parents have had cancer or been treated for cancer is not higher than that in the general population.