Fetal surgery is a well-established and rapidly advancing field within maternal-fetal medicine. This specialized practice involves complex procedures performed on the developing fetus while still inside the uterus. The reality of this technology emerged with the first successful open fetal surgery in 1981. Fetal surgery centers now offer interventions that can prevent irreversible damage and significantly improve the long-term prognosis for children diagnosed with serious congenital anomalies. The goal is to maximize a child’s development by treating the problem at the earliest possible stage.
The Definition and Goals of Fetal Intervention
Fetal intervention is a targeted treatment strategy implemented during pregnancy to address a diagnosed condition in the developing fetus. It is reserved for conditions that are progressive, life-threatening, or those that cause irreversible organ damage if left untreated until after birth. This practice goes beyond routine prenatal surveillance, which focuses only on monitoring health.
The primary objective is to alter the natural course of a disease process before the damage becomes too severe. For example, some conditions cause progressive harm to the central nervous system or lungs throughout the second and third trimesters. By intervening prenatally, specialists aim to mitigate this ongoing damage, improving the viability of the fetus and the quality of life after delivery.
The procedure requires managing the health of both the mother and the fetus simultaneously. The mother is considered an indirect patient who assumes the risks associated with major surgery for the benefit of her child. Therefore, the decision to proceed requires balancing potential risks to the mother against the anticipated benefits for the fetus.
Key Conditions Treated Through Fetal Surgery
Fetal surgery treats a select group of congenital anomalies where prenatal correction offers a distinct advantage over postnatal repair. The first is the in-utero repair of Myelomeningocele (MMC), the most severe form of Spina Bifida. This condition involves the spinal cord and nerves being exposed to the amniotic fluid, causing continuous neurological damage throughout gestation.
Prenatal repair of MMC is typically performed between 23 and 25 weeks of gestation. It aims to cover the exposed defect to protect the nerves. This intervention significantly reduces the risk of needing a ventriculoperitoneal shunt for hydrocephalus after birth and can double the probability that the child will be able to walk independently.
Another condition requiring intervention is Twin-to-Twin Transfusion Syndrome (TTTS). This occurs in monochorionic twin pregnancies that share a single placenta, causing an imbalance of blood flow. Untreated severe TTTS carries a mortality rate as high as 90% if diagnosed before 28 weeks.
A third condition is Congenital Diaphragmatic Hernia (CDH). This involves abdominal organs herniating into the chest cavity through a defect in the diaphragm. This displacement prevents the fetal lungs from growing properly, resulting in pulmonary hypoplasia. A procedure called Fetal Endoscopic Tracheal Occlusion (FETO) may be performed in severe cases to temporarily block the trachea, encouraging the lungs to expand before birth.
Surgical Approaches: Open Versus Minimally Invasive Techniques
Fetal surgery utilizes two main methodologies, selected based on the specific anatomical defect being treated. Open fetal surgery is the most invasive approach, requiring a full surgical opening of the mother’s abdomen and uterus, known as a hysterotomy. This technique is reserved for procedures requiring extensive access and structural repair, such as the closure of Myelomeningocele.
During the open procedure, the uterus is temporarily exposed, and the fetus is briefly moved to allow access to the defect. The team must rapidly complete the repair before closing the uterine incision. Because of the full-thickness uterine incision, the mother will require a Cesarean section for the current and all future deliveries to prevent uterine rupture.
Minimally invasive techniques, primarily fetoscopic surgery, are preferred for many conditions due to lower maternal risk. This approach involves making one or two small incisions in the mother’s abdomen and uterus. A fetoscope, containing a camera and light source, is then inserted into the amniotic cavity.
For TTTS, the fetoscope guides a specialized laser fiber to perform Fetoscopic Laser Photocoagulation (FLP). The laser energy seals off the abnormal communicating blood vessels, functionally dividing the shared placenta to stop the blood imbalance. This approach reduces the mother’s recovery time and minimizes risks.
Selection Criteria and Maternal-Fetal Monitoring
Fetal surgery is a highly selective process. Both the mother and the fetus must meet stringent criteria to ensure the potential benefits outweigh the risks of the intervention. Fetal candidacy requires the anomaly to be confirmed as severe enough to warrant intervention, but without other major structural or genetic abnormalities that would compromise the outcome.
Procedures are bound by a narrow gestational age window, often falling between 16 and 26 weeks. This timing allows the most benefit while minimizing the risk of premature labor. Maternal contraindications include pre-existing conditions like insulin-dependent diabetes, a high body mass index (BMI greater than 40), or a history of previous uterine surgery, all of which increase surgical risks.
Following the procedure, both the mother and fetus require intensive monitoring, often necessitating a prolonged stay in the specialized center. Maternal monitoring focuses on preventing preterm labor and managing complications like premature rupture of membranes. Fetal surveillance involves frequent ultrasounds to assess the repair site and confirm the resolution of the initial problem.
Long-term follow-up is mandatory, extending into childhood, to assess the effectiveness of the prenatal intervention on the child’s neurological and developmental outcomes. The entire process requires a multidisciplinary team, including maternal-fetal medicine specialists, pediatric surgeons, and neonatologists, to manage the continuum of care.