Consanguineous marriage and reproduction in Beirut, Lebanon.

Effects of consanguineous marriages on couples' fertility and on offspring mortality were investigated in Beirut through a population-based health survey of 2,752 households. A multistage random sampling procedure was used, and information was obtained from all ever-married women in the household about their reproductive performance and genealogical relationship with spouse; demographic and socioeconomic information was also recorded. Twenty-five percent of all marriages were between relatives, and the spouses were first cousins in approximately 57% of all consanguineous marriages. Total pregnancies, live births, and living children were significantly higher among consanguineous couples than among nonconsanguineous ones, as was the proportion dead among children ever born. However, no difference remained in either fertility or mortality, when allowance was made for socioeconomic status, religious affiliation, and marriage duration. The issue of confounding is discussed, and the lack of significant pattern in the final analysis is interpreted as resulting from a long-term practice of consanguineous marriages.