The risk of first venous thromboembolism during pregnancy and puerperium in double heterozygotes for factor V Leiden and prothrombin G20210A

Background: The risk of venous thromboembolism (VTE) during pregnancy in double heterozygous carriers of factor (F) V Leiden and prothrombin G20210A is not established. Hence, whether or not these women deserve antithrombotic prophylaxis when pregnant is unknown.Patients and methods: In the frame of a multicenter family study, 52 double heterozygous carriers of FV Leiden and prothrombin G20210A who had remained pregnant at least once before knowledge of thrombophilia, were retrospectively investigated with respect to the occurrence of first VTE during pregnancy and puerperium. They were compared with 104 heterozygous carriers of FV Leiden, 104 of prothrombin G20210A and 104 women without thrombophilia. Results: Double heterozygotes were similar to single heterozygous carriers and non‐carriers for the age at first pregnancy, age at testing and rate of full‐term pregnancies. No VTE during pregnancy was observed in the four groups of women, whereas in the puerperium it occurred in two double carriers (1.8% of pregnancies, 95% CI: 0.5–6.3), three single FV Leiden carriers (1.5%, 0.5–4.3), two single prothrombin G20210A carriers (1%, 0.2–3.6) and one non‐carrier (0.4%, 0–2.5).Conclusions: The risk of first VTE during pregnancy and puerperium in double heterozygous carriers of FV Leiden and prothrombin G20210A is low and similar to that of single carriers. As for single heterozygotes, antithrombotic prophylaxis in asymptomatic double heterozygous carriers appears to be justified only in puerperium.