THE INCIDENCE OF THE FACTOR-V-LEIDEN MUTATION IN AN OBSTETRIC POPULATION AND ITS RELATIONSHIP TO DEEP-VEIN THROMBOSIS

OBJECTIVE: A common missense mutation in the factor V gene, the Leiden mutation, renders factor Va resistant to cleavage inactivation by act ivated protein C and predisposes patients to thrombotic events. We sou ght to evaluate the prevalence of the Leiden mutation and the associat ed thromboembolic events in a community hospital's low-risk obstetric population. STUDY DESIGN: Deoxyribonucleic acid was extracted from who le blood of 407 women. The polymerase chain reaction was used to ampli fy exon 10 of the factor V gene, followed by enzymatic digestion with Mnl 1 for mutation detection. Medical charts were reviewed and patient characteristics, including age, gravidity, parity, obstetric complica tions, medical complications, and mode of delivery, were recorded. RES ULTS: Fourteen or the 407 women carried the factor V Leiden mutation ( 13 heterozygotes and 1 homozygous mutant) for an allele frequency of 3 %, consistent with the published carrier rate. Four of the 14 carriers (28%) had deep venous thrombosis, whereas the frequency of deep venou s thrombosis in this obstetric population was <1%. Another patient car rying the mutation had a consumptive coagulopathy of unknown etiology at 20 weeks' gestation, necessitating delivery. CONCLUSIONS: The Leide n mutation is relatively common in the general obstetric population. T he high rate of deep venous thrombosis noted in our series suggests th e need for genetic testing for this mutation in women with a thromboti c event during pregnancy.