Consanguinity and birth defects in the jerusalem perinatal study cohort

While parental consanguinity is known to increase the risk of birth defects in offspring, it is hard to quantify this risk in populations where consanguinity is prevalent.

To support ongoing studies of cancer and of psychiatric disease, we studied relationships of consanguinity to 1,053 major birth defects in 29,815 offspring, born in 1964-1976. To adjust for confounding variables (geographic origin, social class and hospital), we constructed logistic regression models, using GEE to take into account correlations between sibs. Odds ratios (ORs) and 95% confidence limits were estimated in comparison to a reference group of offspring with grandfathers born in different countries.

With 10.1% of offspring having consanguineous parents, the adjusted OR for major birth defect was 1.41 (1.12-1.74). Offspring of marriages between uncles-nieces, first cousins and more distant relatives showed adjusted ORs of 2.36 (0.98-5.68), 1.59 (1.22-2.07) and 1.20 (0.89-1.59) respectively. For descendents of grandfathers born in the same country, but not known to be related, the OR was 1.05 (0.91-1.21); these showed increased risk associated with ancestries in Western Asia (1.27, 1.04-1.55, p < 0.02) or Europe (1.13, 0.79-1.80).

A strong association of consanguinity with poverty and low education points to the need to avoid exposure to environmental hazards in these families.