Relationship between renal histology and plasma antithrombin III activity in women with early onset preeclampsia.

Renal biopsy was performed in 12 women with the clinical diagnosis of severe, early-onset preeclampsia at the time of cesarean delivery for the express purpose of aiding future counseling on the risk of recurrence. The mean gestation at delivery was 30 +/- 3 weeks. The mean birthweight was 1090 +/- 505 gm. Four women (33%) were multiparous. Antithrombin III activity was determined immediately prior to delivery unrelated to clinical care and as part of other protocols. The biopsy was performed without difficulty in each, although the sample was inadequate in one patient. The clinical diagnosis of preeclampsia was confirmed in nine (82%). However, three of the nine had underlying renal disease, as did the two women without histologic evidence of preeclampsia (42% of the total). Correlations between laboratory parameters with the histopathologic diagnoses were sought. Neither uric acid, creatinine, blood urea nitrogen, platelet count, or 24-hour urinary protein measurements aided the differentiation of the various subgroups. Antithrombin III activity in women with biopsy-supported preeclampsia (77% +/- 12%) was significantly lower than that in women without histologic evidence of preeclampsia (116% +/- 8%). Antithrombin III activity correctly predicted biopsy findings in at least 9 of 11 (82%). These preliminary findings confirm the high frequency of underlying disease in women with early-onset preeclampsia. Although low antithrombin III activity does not differentiate between "pure" preeclampsia and superimposed disease, a normal antithrombin III activity is reassuring and more consistent with a nonpreeclamptic renal complication than with preeclampsia.