Placental surgery: A new frontier

Antenatal ultrasound scanning permits the in utero identification of pathologic pregnancies previously diagnosed after miscarriage or stillbirth by pathologists in laboratories or pediatricians in nurseries. Ultrasound also facilitates the obstetrician's role in the diagnosis of abnormalities at the genetic/molecular level through direct sampling of placental tissue and umbilical cord blood. However, the number of potentially fatal or highly incapacitating fetal conditions which can be successfully treated in utero after diagnosis remains limited. Once the fetus is determined to be abnormal, three alternatives are available: termination of pregnancy, immediate postpartum intervention, or management by some form of in utero fetal therapy. This latter course is undertaken only on the basis of biological need, feasibility, and bioethical acceptability (Micheja and Pringle, 1986). The simplest example fulfilling these criteria is the treatment of hydrops fetalis from Rh incompatibility with fetal transfusions. On the other hand, surgical techniques have been proposed that require incision into the uterus and exteriorization of the fetus, thus breaching the fetus' sterile environment, exposing the mother to the rigors of anesthesia and general surgery, and hysterotomy which may risk the mother's future reproductive capability. Examples of the latter include repair of congenital diaphragmatic hernia and various obstructive uropathies (Harrison, 1990; Harrison and Filly, 1990). Three abnormalities of pregnancy which lend themselves to in utero diagnosis have their pathogenesis in the placenta rather than the fetus per se. These are variations of twin-twin transfusion syndrome (TTTS) in monochorionic (MC) twins, heart failure of the normal 'pump' twin in an acardius twin pregnanc2r and chorioangiomas large enough to cause hydramnios and fetal hydrops. The first two conditions can be traced to chorionic blood vessels connecting the circulations of the twins (chorioangiopagous), whereas the latter is a primary tumor of the placenta. These placental abnormalities are associated with high perinatal morbidity and mortality rates, secondary to premature birth or in utero death, especially when they occur in previable pregnancies where delivery is not an option. With the exeption of the acardius, the associated fetuses are anatomically normal.