Maternal factors in congenital limb-reduction defects.

Various maternal characteristics were examined in case-control studies of limb-reduction defects among live births in Upstate New York (i.e., New York State exclusive of New York City). In a study using birth records of 305 cases and 915 controls born in 1970-81, mean birth weight and gestation length were significantly lower in cases than in controls, and certain pregnancy complications (i.e., abnormal vaginal bleeding and diabetes mellitus) were reported more often in cases than in controls. Several subgroups of defects (i.e., isolated defects vs. multiple, long-bone defects vs. other) were also compared with their respective controls. The subgroup with multiple (including nonskeletal) defects had the lowest mean birth weight and length of gestation. In an interview study of 108 cases and 108 controls born in 1968-74, a history of maternal use of thyroid medication was a significant risk factor; possible explanations for this association are discussed.