Genetic thrombophilic mutations among couples with recurrent miscarriage.

Background: Some cases of recurrent first trimester miscarriage (RM)-the loss of three or more consecutive pregnancies at <12 weeks' gestation-have a thrombotic aetiology.

Methods: We determined (i) the prevalence of three thrombophilic mutations [factor V Leiden (FVL), prothrombin G20210A (PTG) and methylenetetrahydrofolate reductase (MTHFR) C677T] amongst 357 Caucasian couples with RM and 68 parous Caucasian couples with no history of miscarriage and (ii) the prospective outcome of untreated pregnancies amongst couples with RM in which either partner carried a thrombophilic mutation.

Results: The allele frequencies of FVL (2%), PTG (2%) and MTHFR C677T (31%) were similar between cases and controls. The prevalence of multiple thrombophilic mutations (greater than one mutation) was also similar between cases and controls. Amongst couples in whom either partner carried greater than one thrombophilic allele, the relative risk of miscarriage in a future untreated pregnancy was 1.9 (95% confidence interval, 1.3-2.8) compared with those couples who carried no thrombophilic mutation.

Conclusion: The prevalence of thrombophilic mutations is similar in couples with RM and parous controls. In couples with RM, multiple genetic thrombophilic mutations in either partner significantly increases the risk of miscarriage in a subsequent pregnancy.