PARENTAL CONSANGUINITY AS A CAUSE OF INCREASED INCIDENCE OF BIRTH-DEFECTS IN A STUDY OF 131,760 CONSECUTIVE BIRTHS

The risk for birth defects in the offspring of first cousin parents is substantially higher than in the offspring of non-consanguineous pare nts. As a general decline in the frequency of consanguineous marriages was observed in this century, one wonders whether consanguinity is st ill a factor in the appearance of birth defects in developed countries . Based on our registry of congenital anomalies, we think that the ans wer to this question is ''yes.'' In the population studied in Northeas tern France, consanguineous matings were known in 1.08% of the cases w ith congenital anomalies, vs. 0.28% in controls (P < 0.001). The frequ ency of the malformations recorded paralleled the degree of consanguin ity: out of 38 malformed children, 24 were seen in first cousin mating s (10.5 times more frequent than in offspring of nonconsanguineous cou ples), 8 in second cousin marriages, and 6 in more distantly consangui neous matings. Consanguineous mothers were more often pregnant than no nconsanguineous mothers (P < 0.01) and they had more stillbirths than nonconsanguineous mothers. These results must be taken into account wh en counseling consanguineous couples.