Inherited uterine inadequacy: An alternate explanation for a portion of cases of defect

A substantial amount of mental retardation runs in family lines and cannot be attributed to the action of single gene pairs or to chromosomal aberrations. It was hypothesized that one of the causes of this kind of retardation might be an inherited tendency, on the part of females in the family lines, to produce an inadequate uterine environment and hence produce a high proportion of retarded offspring. If so, one would expect sisters and aunts, as compared with brothers and uncles, of retarded propositus cases to produce a higher proportion of retarded (as well as spontaneously aborted, stillborn, or neonatal casualty) offspring. An analysis of data from Reed and Reed, Mental Retardation: A Family Study, supports the hypothesis. Implications of this finding are discussed.