Discordancy for Placental Massive Perivillous Fibrin Deposition and Fetal Growth in Dichorionic Twins after In Vitro Fertilization.

Massive perivillous fibrin deposition (MFD) is a placental lesion of unknown etiology associated with perinatal morbidity and mortality and recurrence risk in subsequent pregnancies. We report a 34 weeks' gestation dizygotic twin pregnancy with discordancy for MFD and for intrauterine growth restriction after in vitro fertilization (IVF). Only the smaller twin corresponding to the placenta affected by MFD showed intrauterine growth restriction, with a weight below the 3rd percentile according to gestational age. The affected placenta showed a moderate increase in decidual lymphocytes. No difference in expression of complement factor C4d in umbilical veins could be observed. Development of MFD in one of the dizygotic placentas may be due to a pathologic immune response to one of the different fetal genotypes as semiallografts. The pathogenetic role of IVF as an environmental factor for development of MFD is unclear.