Pathologic examination of placentas from singleton and twin pregnancies obtained after in vitro fertilization and embryo transfer.

A pathologic investigation was conducted on 100 placentas collected from pregnancies resulting from in vitro fertilization (IVF) and intrauterine embryo transfer (ET), including 70 singleton pregnancies, 20 twin pregnancies, and 10 multiple pregnancies complicated by the vanishing twin (VT) phenomenon (n = 5) or artificially reduced (n = 5). These results were compared with those for 70 spontaneous spontaneous singleton and 20 spontaneous twin pregnancies. In cases of singleton pregnancies, the incidence of abnormal placental shapes was significantly different (P < .025) in the IVF group compared to controls. A significant (P < .005) difference was also observed between these groups in terms of umbilical cord insertion. The mean distance between the cord insertion and the closest placental margin was significantly (P < .001) shorter among IVF singleton pregnancies (3.19 +/- 1.83 versus 4.62 +/- 2.23 cm). In cases of twin pregnancy, no difference was found between IVF and spontaneous pregnancy in the incidence of pregnancy complications and distribution of cord insertion. First-trimester bleeding was the only clinical sign of the disappearance of an embryo in multiple pregnancies complicated by the VT phenomenon and was not observed in multiple pregnancies artificially reduced. The present findings support the hypothesis that marginal cord insertion is secondary to oblique orientation of the blastocyst at the nidation. A larger trial is now required, analyzing the placental features from IVF pregnancies in relation to the etiology of infertility.