Fetal loss in women with hereditary thrombophilic defects and concomitance of other thrombophilic defects: a retrospective family study

Abstract

Objective: To assess the absolute risk of fetal loss associated with hereditary deficiencies of antithrombin (AT), protein C (PC) and protein S (PS), and the contribution of additional thrombophilic defects to this risk.

Design: A retrospective family cohort study.

Setting: A tertiary referral teaching hospital.

Population: Women from families with hereditary deficiencies of AT, PC and PS, and their non-deficient relatives.

Methods: We assessed the absolute risk of fetal loss, comparing deficient women with non-deficient female relatives.

Main outcome measures: Early, late and total fetal loss rates; odds ratios of fetal loss.

Results: We evaluated 289 women, who had 860 pregnancies. The total fetal loss rates were 23% (AT deficient), 26% (PC deficient), 11% (type-I PS deficient) and 15% (type-III PS deficient), compared with 11, 18, 12 and 13% in non-deficient women, respectively. Odds ratios were 2.3 (95% CI 0.9-6.1), 2.1 (95% CI 0.9-4.7), 0.7 (95% CI 0.2-1.8) and 1.1 (95% CI 0.6-2.0), none of which reached statistical significance. Differences were mainly the result of higher late fetal loss rates in women deficient in AT (OR 11.3, 95% CI 3.0-42.0) and PC (OR 4.7, 95% CI 1.3-17.4). The concomitance of factor-V Leiden and prothrombin G20210A was observed in 19% of women, and did not increase the risk of fetal loss.

Conclusions: Although absolute risks of fetal loss were high, odds ratios of total fetal loss were not statistically significant in deficient versus non-deficient women. However the higher absolute risks appeared to reflect higher late fetal loss rates as opposed to early fetal loss rates. An additional effect of concomitance of factor-V Leiden and prothrombin G20210A was not demonstrated, which may result from the exclusion of women at highest risk of venous thromboembolism, or from the small numbers sampled in the study.