Frequency of factor V-Leiden and prothrombin G20210A in placentas and their relationship with placental lesions

The most common hereditary hypercoaguable states are factor V-Leiden (FVL) and prothrombin mutations (PRO). FVL and PRO present with an incidence of a pproximately 5% in a heterogeneous population, and 45% to 63% of the thromb ophilic population. The frequency of these mutations in the fetal populatio n and their clinical importance is unknown. Fetal side thromboembolic event s (FST) include congenital stroke and renal vein thromboses. In some cases, FST can be diagnosed by placental histopathology when avascular (infarcted ) villi are present in a patent maternal vascular space. FST can present as placenta-fetal-vascular or fetal-visceral-vascular lesions. Causes include vascular damage from cord compression or inflammation, but most remain unc lear. Potential causes of FST include FVL and PRO. We describe the incidenc e of FVL and PRO from a prospective group of 169 consecutive placentas and in a retrospective group of archived placentas diagnosed with placental FST . One each of FVL and PRO heterozygosity was found in the prospective set ( <1% incidence for each). Five prospective placentas were diagnosed with pla cental FST, for an incidence of 3%; all were wild-type for FLV and PRO. Twe nty-seven of 65 archived FST cases had analyzable DNA to find 5 FVL heteroz ygotes (18.5%); all were wild-type for PRO. Twenty-one of 65 retrospective archived controls analyzable found 1 case of FVL heterozygosity (<5%). We f ind that the frequency of FVL and PRO may be decreased in the pregnant popu lation but increased in cases of placental FST. Because factor V Leiden het erozygosity carries an increased risk for thrombotic complications, we sugg est placental diagnosis of fetal side thromboemboli warrants clinical evalu ation for FVL in infant and potentially the parents. Copyright (C) 2000 by W.B. Saunders Company.