Pregnancy outcomes among women with inherited thrombophilia polymorphisms

Asymptomatic, nulliparous, heterozygous carriers of the prothrombin gene mutation are 3.6 times as likely as women who do not carry the mutation to experience severe pregnancy complications, including severe preeclampsia, fetal growth restriction less than the fifth percentile for sex and gestation, stillbirth, and neonatal death, according to a prospective cohort study conducted in Australia.

The authors of the study, which involved 1,707 women, found particularly strong associations between heterozygosity for prothrombin gene mutation and placental abruption (odds ratio [OR], 12.15; 95% confidence interval [CI], 2.45-60.39) and between homozygosity or heterozygosity for factor V Leiden and stillbirth (OR, 8.85; 95% CI, 1.60-48.92), although the latter finding involved a very small number of patients (n=6).

They also found that homozygosity for the methylenetetrahydrofolate reductase enzyme (MTHFR) A1298C polymorphism may actually be protective against such adverse pregnancy outcomes, particularly severe fetal growth restriction.