OBJECTIVETo provide genetic consulting and prenatal diagnosis for two families with congenital factor V deficiency based on the known mutations of factor V gene (G16088C and G69969T).

METHODSChorionic DNA was obtained at 12 weeks of gestation and analyzed to exclude maternal cell contamination through microsatellite DNA analysis. It was then amplified with PCR and sequenced to determine the presence of mutations in exons 3 and 23. Factor V activity of the blood was assayed at 22 weeks of gestation and 6 months after birth.

RESULTSThe fetus in case 1 was found to be a heterozygous carrier of the G16088C mutation, for whom factor V activity of the cord blood and peripheral blood were 15% and 53%, respectively. Fetus 2 did not carry the familiar G69969T mutation, for whom the factor V activity of cord blood and peripheral blood has measured 32% and 93%, respectively. Follow-up studies demonstrated that the two infants were both in good health without a tendency for bleeding.

CONCLUSIONIn both cases, the genotypes were consistent with the phenotypes. This is the first report of prenatal diagnosis of congenital factor V deficiency.