ABSTRACT
Assisted reproduction (ART) currently includes a variety of technologies; the two most frequently used are in vitro fertilization and embryo transfer (IVF/ET), and intracytoplasmic sperm injection and embryo transfer (ICSI/ET)652. There are few studies of the placentas from these assisted gestations and the majority of studies have evaluated IVF/ET. The incidences of abnormal placental shapes, such as bilobate and accessory lobated placentas, have been found to be significantly increased in IVF/ET singleton pregnancies, in some non-blinded and/or non-controlled studies68,653, but the incidences of these gross findings were not identified to be significantly different in the blinded and controlled study of ART placentas by Daniel and colleagues652. Histology was also not identified to be significantly different between study and control placentas in their study, nor was it appreciated to be different in the IVF/ET placentas evaluated by others68,653. However, all investigators have noted an increased incidence of marginal (<2 cm from the placental margin) and/or velamentous insertion of the cord68,652,653. These changes may relate to orientation of the blastocyst at implantation or to abnormalities of the reproductive tract (e.g. leiomyomas, endometriosis, sequelae of pelvic inflammatory disease) that were responsible for the infertility problem that led to the need for ART in the first place. Superficial implantation has also been proposed to be a factor, but, since Daniel and colleagues652 found no differences in the rates of abnormal placental shape, this remains a debated cause. Increased placental: fetal weight ratio and placental thickness have been identified in one study652, and postulated to be due to ART-related endometrial hyperstimulation from hormonal administration and multiple embryo transfer procedures that may alter the endometrium both histologically and biochemically. Of note is that infertility per se increases the risk of low birth weight and preterm birth, so it seems plausible that the effects of hormonal stimulation and/or multiple embryo transfer may confer ‘advantage’ in assisted gestations, including, perhaps, continuation to term. Gavrill and colleagues653 found no differences between spontaneous twin gestations and those of IVF/ET in terms of pregnancy complications. Multiple pregnancies are more common in pregnancies achieved with IVF/ET and ICSI/ET, and vanishing twins or other multiples may occur spontaneously, or artificial reduction may have been performed. In these cases, particularly after artificial reduction, remnant nodules may be seen on the fetal surface. Radiography of these placentas may show fetal skeletal remnants on the surface.
