The prevalence of autoantibodies in pregnant and nonpregnant women.

The frequency of autoantibodies during pregnancy was studied. Sera from 136 women (84 pregnant and 52 nonpregnant) were tested for antibodies directed against nuclear antigens, smooth muscle antigens, gastric parietal cells, mitochondria, and striated muscle by indirect immunofluorescent microscopy. Rheumatoid factor was measured by a latex agglutination test, and thyroid microsomal and thyroglobulin antibodies were measured by a hemagglutination assay. Immunofluorescence assays were considered positive if antibodies were detected at a serum dilution of 1:20. All positive samples were retested at increasing dilutions until immunofluorescence or agglutination could not be detected. The control population consisted of 52 normal, healthy, ovulatory, and nonpregnant women. The study population consisted of 84 pregnant women, none of whom had a known autoimmune disorder. The mean ages of the two groups were 32 and 26 years, respectively. The frequency of autoantibody detection was not significantly different in comparing the study (46.2) and control groups (40.5). The results did not support the hypothesis that pregnancy has an effect on the induction or suppression of autoantibody production. Previous studies that suggested differences may have been influenced by the lack of a control group.