Fetal interventions have undergone three major paradigm shifts over the past several decades related to the invasiveness of the procedure. The landmark work of Liley and others in the 1960s to develop fetal transfusion techniques to treat severe fetal anemia ushered in the possibility of providing in utero fetal therapy. The pendulum swung from minimally invasive needle and shunt procedures to the maximally invasive methods of open fetal surgery. The initial enthusiasm for open fetal surgery in the United States of the 1980s waned after realization of the not insignificant rate of maternal morbidity and relatively high rate of prematurity. In the 1990s the pendulum swung back to minimally invasive methods, which included operative fetoscopy. The advantage of operative fetoscopy and other minimally invasive fetal interventions is the relatively nominal violation of the sanctity of the human womb, which has resulted in negligible maternal morbidity and significantly decreased risk of prematurity.

The concept of the fetus as a patient is a complicated topic that can be addressed from an embryologic, ethical, theologic and/or legal vantage point. It is important as physicians to be cognizant with each of these issues without interjecting personal bias when counseling parents. Once a fetal abnormality has been identified, it is the physician’s job to educate the parents about the particular findings, the natural history of the condition, and the spectrum of expected prognoses. The parents should be educated in a nondirective manner regarding all management options. When a mother seeks care from a physician regarding a fetal condition, the fetus should be treated as a patient and be afforded all the opportunities for modern medical care.

Like any patient in medicine, the fetus requires appropriate pain management during invasive procedures. There is controversy in the literature regarding the gestational age at which the fetus has the capacity to perceive pain. Histologic examinations of the spinal cord have identified neurons involved in nociception before 20 weeks’ gestational age. Invasive procedures elicit a stress response in fetuses as early as 16 weeks’ gestation, while providing fentanyl during fetal interventions has been shown to diminish this stress response. Because of uncertainty over the exact developmental timing at which the fetus may perceive pain, fetal anesthesia and analgesia should be provided during all direct fetal interventions regardless of gestational age.

Open fetal surgery is a fetal intervention in which the gravid uterus is opened to allow direct surgery on the fetus. The surgery is performed under relatively deep general anesthesia to provide uterine quiescence. Maternal laparotomy and hysterotomy are performed, and the fetus is then partially exposed to allow direct surgical access to the fetal lesion. With minimal manipulation of the umbilical cord, the fetus is maintained on placental support throughout the procedure. After the surgical repair, the fetus is returned into the uterus and the uterine incision and the abutting fetal membranes are sutured closed. The mother is hospitalized for at least 3 days, with often 1 day spent in the intensive care unit. Due to the hysterotomy, the mother will require a cesarean section for that pregnancy and all subsequent pregnancies. Essentially all patients deliver prematurely.

The indications for open fetal surgery have been dwindling over the past decade. Congenital anomalies that have been treated via open fetal surgery include congenital diaphragmatic hernia, pulmonary sequestration, congenital cystic adenomatoid malformation of the lung, sacrococcygeal teratoma, and myelomeningocele. Aside from myelomingocele, all these lesions have been successfully treated via operative fetoscopy or needle/shunt procedures. A study comparing outcomes of myelomeningocele repair by open fetal surgery versus traditional repair after birth should be completed by 2011. Because of the intrusive nature of open fetal surgery and the relatively high risk of maternal and fetal morbidity compared to other fetal interventions, this technique is not expected to play a major role in fetal therapy in the future.

Using several of the surgical techniques developed for open fetal surgery, the ex utero intrapartum treatment (EXIT) procedure was developed to treat the term or near term fetus with an extensive airway obstruction. A classic cesarean section is performed and the fetus is partially exteriorized. Without disruption of the placenta and while attempting to maintain blood flow through the intact umbilical cord, surgical access to the airway is obtained. Placental support is discontinued once the airway is secured by clamping and cutting the umbilical cord.

Operative fetoscopy is a therapeutic modality that strikes a fine balance between surgical access and minimal invasiveness. Using local anesthesia and intravenous maternal sedation, an endoscope that measures up to 3.3 mm in diameter is inserted through the maternal abdomen into the uterus. Intraoperative ultrasound guidance is used to guide trocar insertion. Most surgeries are performed using a single port. The operating channel of the endoscope allows for the use of various surgical instruments. The interlacing muscle fibers of the uterine wall spontaneously seal the uterine insertion site upon removal of the trocar. Recovery for the mother is uncomplicated, and she is usually discharged home after a 1-night hospital stay. Operative fetoscopy may be performed any time after 16 weeks’ gestation. The patient may deliver vaginally in the index pregnancy as well as in all subsequent pregnancies.

The cornerstone of most fetal therapy centers is the treatment of twin–twin transfusion syndrome (TTTS) via operative fetoscopy. TTTS is a condition that develops in 10–15% of monochorionic twins from unbalanced sharing of blood through vascular communications in the shared placenta. A series of pathophysiologic changes ensues from the net shunting of blood from one twin (donor) to the other twin (recipient), resulting in donor twin oligohydramnios, recipient twin polyhydramnios, and characteristic anatomic and arterial/venous flow derangements that can be identified by ultrasound.