The prevalence of autoantibodies and lupus anticoagulant in healthy pregnant women.

Abstract

Abnormal autoantibodies have recently been implicated in pregnancy wastage. The normal autoantibody profile of pregnancy has so far, however, not been established. We investigated the effect of pregnancy on autoantibody production prospectively and longitudinally. Forty-three healthy pregnant women were compared with 50 nonpregnant healthy controls matched for age, race, and various obstetric and medical indices. All sera were tested for total immunoglobulin (Ig) levels; IgG, IgM, and IgA isotypes of autoantibodies to six phospholipids; total histone and four histone subfractions; and four polynucleotides. Plasma samples were evaluated for the presence of lupus anticoagulant. Total IgG decreased significantly in pregnant patients. The majority of autoantibody levels in pregnant women were within normal nonpregnant ranges. Only a few autoantibodies were increased in early pregnancy, including IgG antiphosphatidylinositol and H 2B, IgM antiphosphatidylinositol and phosphatidic acid, and IgA antiphosphatidylinositol and H 4. Most autoantibodies, although increased at term, were still within the normal nonpregnant range. Normalizing the data for expanded plasma volume did not significantly alter these results. Adjustment regression analysis excluded age, race, and various medical and obstetric indicators as confounding variables for autoantibody levels. The expected and observed prevalence of positive autoantibody levels in pregnant women was not significantly different from that of nonpregnant controls. None of the pregnant women demonstrated positive lupus anticoagulant. We conclude that in normal pregnancy between 16 weeks' gestation and term, autoantibody levels are largely within the normal range. Alterations occur, if at all, at the time of delivery.