Fetal Surgery for Sacrococcygeal Teratoma

Sacrococcygeal teratoma (SCT) is the most common congenital germ cell tumor,[1]  with an incidence of 1 in 35,000-40,000 live births[2] and a female predominance (3:1-4:1 ratio).[2, 3]  There is no clear geographic predominance, but a higher prevalence has been observed in Finland.[4]  The majority of cases are sporadic, with no definitive familial tendency.

In 11% of cases, patients also have associated congenital anomalies, often anorectal malformations.[5]  Rare cases of SCT can be associated with congenital anomalies representing the Currarino triad (sacral body defects, anorectal anomalies, presacral mass/SCT).

SCT arises from embryologically multipotent cells from the Hensen node, which is located in the coccyx.[6, 7]  Most SCTs are now diagnosed antenatally as a consequence of the widespread use of routine obstetric ultrasonography (US).[8] The majority are diagnosed in the second trimester via US, on which the earliest sign may be increased uterine size for gestational age.[9] Rarely, the diagnosis is made earlier; the earliest case described was diagnosed at 13 weeks' gestation.[10]  The differential diagnosis includes meningocele, myelomeningocele, neuroblastoma, perineal cyst, lymphangioma, lipoma, or enteric duplication cyst.[9]

The timing of diagnosis has implications for prognosis. Patients with postnatally diagnosed SCT typically do well after early surgical resection, and the main cause of the rare mortality in these patients is attributed to malignancy. Patients with antenatally diagnosed SCT, however, have a mortality in the range of 30-50%,[11, 12, 13] attributable to poor prognostic factors (eg, solid tumor morphology and increased tumor vascularity). Whereas some fetuses are born without complications, others can develop high-output cardiac failure, nonimmune hydrops fetalis (hydrops), and, ultimately, fetal demise.

This wide disease spectrum has prompted several fetal treatment centers to identify US predictors of survival for fetuses with SCT in an effort to helpdetermine which high-risk fetuses may benefit from fetal intervention. Poor prognostic factors on US imaging include signs of hydrops (eg, subcutaneous edema, ascites, or pleural effusion) or high-output cardiac failure (eg, inferior vena cava [IVC] dilation, absent/reversed ductus venosus flow, elevated combined ventricular cardiac output, or placentomegaly).[14, 15, 16]

The key to optimizing survival in these fetuses is intervention before the development of high-output cardiac failure, hydrops, and maternal mirror syndrome. Evaluation of tumor characteristics and echocardiographic findings aid in identifying fetuses at increased risk for these complications, who may derive the greatest benefit from fetal intervention.[17]

Pathophysiology

The vascular supply to an SCT commonly arises from the middle sacral artery, which can enlarge to the size of the common iliac artery and cause a vascular steal syndrome.[18] These large vascular tumors can lead to high-output cardiac failure as a consequence of arteriovenous shunting through the tumor, resulting in placentomegaly, hydrops, and, ultimately, fetal demise.[18]

Polyhydramnios is commonly seen due to increased fetal cardiac output, which often leads to preterm labor and premature rupture of membranes (PROM). Conversely, oligohydramnios can also occur if an intrapelvic portion of the tumor causes significant urinary obstruction.[3]

In severe cases, maternal mirror syndrome may develop, in which the mother manifests symptoms that mimic those of the hydropic fetus. These symptoms are similar to those of severe preeclampsia, such as hypertension, emesis, peripheral edema, pulmonary edema, and proteinuria.[12]

Fetal surgery is contraindicated after maternal mirror syndrome has developed. Mothers who may have maternal mirror syndrome must be monitored very closely, and delivery or pregnancy termination may be required for maternal safety.

Classification

SCTs are categorized according to the classification developed by the American Academy of Pediatrics, Surgical Section (AAPSS), as follows[19] :

• Type I - Primarily external (with or without a minimal internal/presacral component)
• Type II - Predominantly external, but also has a significant intrapelvic component
• Type III - Predominantly intrapelvic with abdominal extension, but also has a small external component
• Type IV - Entirely internal within the pelvis and abdomen

Whereas type I tumors, being primarily external to the fetus, are easily diagnosed antenatally and are amenable to fetal resection, type IV tumors can be difficult to diagnose and are not amenable to fetal resection.[8, 20] Thus, although the AAPSS classification describes surgical anatomy and identifies tumors that are amenable to fetal resection, it does not provide prognostic information,[3] nor does it identify fetuses who would benefit from fetal intervention.

Fetuses with SCT are considered for fetal resection or fetal intervention only in extreme cases and are evaluated on a case-by-case basis.

Small tumors without significant vascularity are unlikely to affect the fetus significantly.[3] These fetuses are unlikely to develop high-output cardiac failure or hydrops and can be monitored throughout gestation with serial US. Serial US is used to evaluate tumor size/growth, solid/cystic morphology, amniotic fluid volume, vascular flow, and fetal hydropic changes.[21, 22]

When there are signs of placentomegaly and hydrops after fetal lung maturity (usually after 32 weeks), the fetus is delivered on an emergency basis. Only fetuses of less than 26 weeks' gestation with signs of impending hydrops who have tumors amenable to surgical resection (AAPSS type I or type II) are considered for open fetal surgery (ie, tumor debulking).[11, 20] Fetuses of 26-30 week's gestation with impending hydrops can also be considered for fetal intervention, but the potential risks and benefits of open fetal surgery versus ex-utero intrapartum treatment (EXIT) to resection should be weighed.[23]

As with all invasive procedures, the risks and benefits of fetal intervention must be considered for each patient. However, considerations of the risk to and safety of the pregnant mother are unique to fetal surgery. Before fetal intervention is considered, a multidisciplinary team should counsel and evaluate each family. The evaluation should include the following[20, 24] :

• Detailed US to confirm the diagnosis, evaluate tumor characteristics, and detect any other anatomic abnormalities
• Fetal magnetic resonance imaging (MRI) for additional anatomic information (eg, spinal tumor extension, colonic displacement, or genitourinary obstruction) ^{[25, 26]}
• Fetal echocardiography to rule out congenital heart disease and to assess fetal cardiac function
• Amniocentesis for fetal karyotyping

In 2009, Wilson et al proposed the following criteria for surgical resection of SCT[27] :

• No maternal contraindications for fetal surgery (eg, presence of prohibitive medical or surgical comorbidities, body mass index [BMI] >36, or inability to tolerate anesthesia)
• Fetal gestational age of 20-30 weeks
• A favorable AAPSS stage and no additional congenital anomalies
• Impending hydrops (evidence of ascites, pleural effusion, subcutaneous edema, or pericardial effusion)
• Normal fetal karyotype
• Fetal cardiac output greater than 600-900 mL/kg/min (adjusted for gestational age)

Contraindications for fetal intervention for SCT include the following[27] :

• Significant placentomegaly (placental thickness at cord insertion >35-45 mm with gestational age < 30 wk)
• Maternal mirror syndrome
• Multiple gestation
• Chromosomal abnormality
• Other fetal anatomic abnormalities

Several institutions have reported outcomes with and without fetal intervention for antenatally diagnosed SCT.[28, 29, 30, 31, 32] Of patients with antenatally diagnosed SCT, 36-41% require fetal intervention.[29, 30]

Mortality due to SCT is mainly attributed to tumor morphology; small cystic SCTs rarely cause problems in utero. In contrast, rapid growth of large vascular tumors can lead to rupture and hemorrhage either in utero or during delivery; this is usually fatal.[20]

The overall survival rate of fetuses with antenatally diagnosed SCT is 47-83%,[28, 30, 31] but the survival rate after fetal surgery is 50-75%.[28, 29, 30, 31] It is important to note, however, that survival after fetal intervention should be compared with survival in the subgroup of patients with hydrops and no intervention, in whom the survival rate approaches 0%.[33, 34]

About 40-50% of survivors with antenatally diagnosed SCT have long-term morbidity, which may include obstructive uropathy or dissatisfaction with cosmetic outcomes. In addition, damage to the sacral nerves caused by the tumor itself or damage occurring during SCT resection can result in bowel/bladder incontinence, lower-extremity palsy, or sexual dysfunction at reproductive age.[28, 32, 35, 36]

Prognostic indicators

Placentomegaly and hydrops are harbingers of fetal demise in SCT.[12, 37] The presence of hydrops greatly increases the odds of fetal demise in fetuses with SCT (odds ratio, 21.0).[38]

A retrospective review of 17 fetuses with antenatally diagnosed SCT treated at the University of California, San Francisco (UCSF), between 1986 and 1998 evaluated the factors associated with hydrops.[17] There was a significant difference in tumor morphology (solid vs cystic) and vascularity in fetuses who developed hydrops as compared with those who did not. In addition, fetuses who developed hydrops were diagnosed at an earlier gestational age (19 vs 25 wk) and were delivered at an earlier gestational age (28 vs 38 wk).[17]

In this series, 12 fetuses developed hydrops, four of whom survived.[17] Of the four survivors, three underwent fetal intervention because they developed hydrops before viability, and one developed hydrops at 32 weeks' gestation and was delivered immediately. All fetuses who did not develop hydrops survived.

Similar retrospective reviews also identified cystic morphology as a positive prognostic factor, with solid morphology and tumors with high vascularity being associated with an increase in adverse outcomes.[39, 40]

These studies show that fetuses with predominantly solid and highly vascular tumors are at an increased risk for developing hydrops, which then increases the risk of fetal demise. These patients should undergo close follow-up throughout gestation with serial US and echocardiography and may be considered for fetal intervention upon signs of impending hydrops.

A retrospective review of 23 patients with antenatally diagnosed SCT who were evaluated at the Children’s Hospital of Philadelphia (CHOP) between 2003 and 2006 showed that SCTs with a growth rate exceeding 150 cm3/wk are associated with increased perinatal mortality.[27] A subsequent retrospective review from Zhejiang University (China) for the period between 2014 and 2021 found that a tumor growth rate higher than 48 cm3/wk was also associated with a poor prognosis (sensitivity, 100%; specificity, 78.3%; area under the curve [AUC], 0.880).[41]

In a study from UCSF that retrospectively reviewed 28 fetuses with antenatally diagnosed SCT between 1991 and 2005, solid tumor volume–to–head volume ratio (STV/HV) on US was identified as a predictor of poor outcomes.[42] All patients with an STV/HV lower than 1 survived, whereas 61% of fetuses with an STV/HV higher than 1 did not.[42]

In addition, the study determined that 97.3% of fetuses with an STV/HV higher than 1 were associated with one or more abnormal US findings, such as polyhydramnios, hepatomegaly, placentomegaly, cardiomegaly, ascites, pericardial effusion, or integumentary edema.[42] With serial US, increases in the STV/HV ratio can guide management of fetal SCT so that fetal intervention or early delivery can be performed before hydrops develops.[43]

In a study from the Fetal Center at Texas Children’s Hospital, tumor volume–to–fetal weight ratio (TFR) was a marker of poor outcome in 12 fetuses with SCT between 2004 and 2009,[33] With the use of MRI or US, tumor volume was determined via the prolate ellipsoid formula and fetal weight via the Hadlock formula. A TFR higher than 0.12 before 24 weeks' gestation predicted poor outcomes (fetal hydrops, demise, or neonatal death) with 100% sensitivity, 83% specificity, a negative predictive value of 100%, and a positive predictive value of 80%.[33]

Of the 12 fetuses with SCT in this series, 33% (4/12) developed hydrops.[33] All fetuses who developed hydrops had a TFR higher than 0.12 by 24 weeks' gestation, and three fetuses died. One patient underwent fetal intervention after hydrops developed and survived. Thus, TFR may be used to identify fetuses with SCT who are at risk for poor outcomes before 24 weeks' gestation and who may benefit from fetal intervention.

A TFR higher than 0.12 in combination with tumor morphology was further validated as a sonographic predictor of poor prognosis in subsequent retrospective studies from UCSF,[14] Zhejiang University (China),[41] and CHOP.[44] In addition, a TFR higher than 0.12 has been associated with increased maternal operative risk.[44]

In a review of 79 fetuses with antenatally diagnosed SCT at three fetal centers from 1986 to 2011, receiver operating characteristic (ROC) analysis revealed that a TFR higher than 0.12 before 24 weeks' gestation was predictive of a poor prognosis, as was solid tumor morphology and the presence of hydrops.[45] However, none of these factors were found to be independent predictors of a poor prognosis on multivariate analysis.

In a retrospective review of 28 pathology-confirmed isolated SCT patients evaluated with at least two documented US scans and followed through hospital discharge between 2005 and 2012, a faster SCT growth rate (calculated as the difference between tumor volume on a late-gestation sonogram and that on an early-gestation sonogram, divided by the difference in time) was associated with adverse outcomes (death, high-output cardiac failure, hydrops, and preterm delivery).[46]

SCT can create a low-resistance large arteriovenous shunt, which can progressively increase preload and afterload on the fetal heart, leading to volume overload, ventricular dilation, ventricular hypertrophy, and high-output cardiac failure.[47] A 10-year retrospective review of seven fetuses showed that the most important prognostic criteria for maternal and fetal complications due to antenatally diagnosed SCT included cardiomegaly, hydrops, and increased preload indices of the fetal venous system.[48] Fetuses with SCT and cardiomegaly exhibit increased odds for developing an adverse outcome (odds ratio 10.3).[38]

Studies on fetuses with SCT show that combined cardiac output increases dramatically before the development of hydrops.[49, 50]  Fetuses with combined cardiac output that exceeded 700-800 mL/kg/min died in utero.[47] Rychik et al analyzed the acute cardiovascular effects of fetal surgery in four patients with SCT and saw a significant decrease in combined cardiac output (690 ± 181 mL/kg/min vs 252 ± 82 mL/kg/min) after fetal resection of SCT.[51]

In a retrospective review of 11 fetuses with SCT, those with poor outcomes (hydrops, fetal demise, neonatal death) had a cardiothoracic ratio greater than 0.5, a combined ventricular output greater then 550 mL/kg/min, tricuspid or mitral valve regurgitation, or a mitral valve Z-score greater than 2.[15] Identifying these cardiovascular indicators as poor prognostic factors aids in the identification of patients at high risk for fetal demise and can prompt fetal surgical intervention before the development of hydrops.

After evaluation at a fetal treatment center, families should undergo extensive multidisciplinary counseling. Specialists should include fetal/pediatric surgeons, obstetricians, perinatologists, and anesthesiologists, as well as a social worker and nurse coordinator to discuss the risks and benefits of fetal intervention. Potential risks of fetal intervention include the following[20] :

• Preterm labor
• Uterine disruption
• Rupture of membranes
• Chorioamnionitis
• Side effects of tocolytics (used to prevent preterm labor)
• Maternal pulmonary edema
• Fetal demise

Additional risks of fetal surgery include bleeding, need for blood transfusion, and wound infection.

An experienced operative team is essential and usually includes the following[20] :

• Two pediatric surgeons
• Perinatologist
• Ultrasonographer/echocardiographer
• Experienced operating room personnel
• Pediatric/obstetric anesthesiologist

The team should also have blood products prepared for potential intraoperative transfusion. Patients needing fetal intervention usually have highly vascular solid tumors, which were shown to have increased transfusion requirements in a retrospective study that evaluated 112 cases of operative management of sacrococcygeal teratoma (SCT), including six in-utero repairs.[52]

Open fetal surgery and ex-utero intrapartum treatment procedure

The following are used for maternal perioperative monitoring in open fetal surgery and the ex-utero intrapartum treatment (EXIT) procedure:

• Blood pressure cuff
• Large-bore intravenous (IV) catheters
• Bladder catheter
• Electrocardiographic (ECG) leads
• Sequential compression devices
• Pulse oximeter

Also necessary for open fetal procedures are the following:

• Intraoperative ultrasound device
• Uterine stapler
• Large ring retractor
• Sterile neonatal pulse oximeter and IV catheter for the fetus
• Fluid warmer
• Sterile neonatal laryngoscope and endotracheal tube (for the EXIT procedure)

Minimally invasive techniques

Equipment for minimally invasive techniques includes the following:

• Intraoperative ultrasound device
• LeVeen radiofrequency probe (8 prong) for radiofrequency ablation (RFA)
• Fetoscope (1.9 mm, 60°) for laser ablation
• Neodymium-doped yttrium-aluminum-garnet (Nd:YAG) laser fiber (0.4 mm) for laser ablation

Patients are usually admitted to the obstetric ward the evening before fetal surgery.  Preoperatively, indomethacin, magnesium sulfate, or both are given to prevent uterine contraction during the procedure, and antibiotics are given prophylactically to prevent infection.

Anesthesia

Anesthesia for open fetal surgery includes maternal epidural and general anesthesia. This provides anesthesia to both the mother and the fetus and ensures uterine relaxation during the procedure.[20, 53]  Volatile anesthetics can cross the placenta and decrease fetal cardiac function; maternal anesthesia with IV nitroglycerin and/or epidural anesthesia can limit the amount of volatile anesthetic required.[54]  Epidural anesthesia also decreases uterine contractions during the postoperative recovery period.

Anesthesia options for minimally invasive techniques can range from spinal anesthesia with local anesthetic to general anesthesia, depending on the patient and the circumstances for fetal intervention. During the procedure, intramuscular injection of pain medication and a paralytic agent can be administered to the mother under ultrasonographic (US) guidance.[55]

In a systematic review of anesthetic techniques for fetal operative procedures, 168 studies up to December 2021 demonstrated no difference in perioperative outcomes between maternal-only anesthesia (MA) and maternal-and-fetal anesthesia (MFA)[56] ; however, evaluation of open fetal surgery cases (including open fetal SCT resection) identified increased rates of premature rupture of membranes (PROM) and fetal death in cases using MFA. The agents most commonly used for fetal anesthesia are fentanyl, atropine, and curare paralytic agents (vecuronium or pancuronium).[56]

Positioning

The mother is placed in a supine position on the operating room table, with the right side elevated to decrease the pressure of the uterus on the inferior vena cava (IVC).[20]

Depending on the postoperative course, patients can be discharged within a week after fetal surgery, though they will need to stay at a facility near the fetal treatment center. Activity is gradually modified if there is minimal uterine irritability. US is performed twice a week to assess fetal development and resolution of hydrops. Because of the location of the hysterotomy, the mother will require cesarean delivery for all future deliveries.

Fetal surgery for sacrococcygeal teratoma (SCT) remains challenging; it should be considered only in select fetuses with impending hydrops and performed only at experienced centers.[57, 58]  The purpose of fetal intervention is to debulk the tumor, with the understanding that formal oncologic resection will be performed postnatally.[59]  The key to successful fetal intervention is identifying fetuses before the onset of hydrops, as well as identifying fetuses who may best be served by early delivery rather than fetal intervention.

Fetal exposure for SCT resection is similar to what has been reported for other open fetal surgical procedures.[20]

The uterus is exposed through a Pfannenstiel incision. If the placenta is located posteriorly, the superior and anterior skin and subcutaneous tissue flaps are created, and a midline fascial incision is then created to expose the uterus (see the image below).

An anterior hysterotomy is performed while the uterus remains in the abdomen. However, if the placenta is located anteriorly, the rectus muscles will have to be divided in order to prevent uterine vascular compromise as the uterus is lifted out of the abdomen to perform a posterior hysterotomy.

A large ring retractor is used to maintain exposure.[20]

Intraoperative sterile ultrasonography (US) is used to delineate the position of the fetus and the placenta (see the image below), and continuous echocardiography is used to monitor fetal well-being throughout the operative procedure.

If the pregnancy is complicated by polyhydramnios and placentomegaly, the true edge of the placenta is not always appreciated on US, and the hysterotomy should be planned even farther away from this edge.

Stay sutures are placed on the uterus, and a small hysterotomy is made, which is then extended with a stapler designed especially to be used on the uterus (see the image below).[60] In view of the use of anesthetic agents that cause uterine relaxation, the uterine stapler is crucial for limiting blood loss. This hemostatic stapler is also important for securing the membranes to the uterine wall to prevent separation of membranes. Once the hysterotomy is performed, the fetus is positioned so that the tumor is exposed through the hysterotomy.

A "fetal cocktail,” which consists of a paralytic agent (either pancuronium or rocuronium) and fentanyl, is administered to the fetus via an intramuscular (IM) injection. A pulse oximeter is placed on the fetus to monitor fetal well-being (see the first image below). Intravenous (IV) access is obtained for administration of fluids, blood, or medication (see the second image below). Use of this strategy of fetal monitoring during open fetal surgery allows administration of fluids in response to changes in preload during the resection and may improve fetal survival.[61]

The fetus is kept buoyant and warm in the uterus with continuous infusion of warmed lactated Ringer solution (LRS) into the uterus.

After the SCT is resected, a two-layer uterine closure is performed. Before the uterus is completely closed, however, LRS is instilled into the uterus until US shows that normal amniotic fluid volume has been restored.

An omental flap can be secured over the hysterotomy, and the fascia, subcutaneous tissue, and skin are closed.

In some cases, early delivery of the fetus without SCT resection has led to adverse events between delivery and neonatal resection (eg, tumor hemorrhage and fetal exsanguination). In cases where delivery and tumor resection may lead to hemodynamic instability, the ex-utero intrapartum treatment (EXIT) procedure may be considered. EXIT-to-resection of fetal SCT is used in fetuses after 32 weeks' gestation (and may be considered for a fetus of 27-32 weeks' gestation) with a large vascular type I or II tumor necessitating early delivery in the absence of maternal contraindications.[43, 23]

The EXIT procedure, originally developed to establish an airway in a fetus with airway compromise while the fetus is still connected to placental circulation for oxygenation, has been adapted for intervention in fetuses with other anomalies who may experience instability during birth.[62] For fetuses with SCT, the EXIT procedure allows tumor debulking to interrupt the vascular steal phenomenon, which minimizes preoperative manipulation and trauma to the tumor.[43] The infant can be safely delivered and stabilized before definitive oncologic resection.

The EXIT procedure is performed with the mother under general anesthesia to maximize uterine relaxation and uteroplacental blood flow.[63] The hysterotomy, fetal monitoring, and fetal IV access are performed as described for open fetal surgery.

After debulking of the tumor, the fetus is intubated and given surfactant before the umbilical cord is clamped. The hysterotomy, fascial, and skin closures are performed in the same fashion as in open fetal SCT resection.

Roybal et al reported one survivor with this technique, who had neurologic complications due to tumor invasion into the spinal canal.[43] Surgeons at the University of California, San Francisco (UCSF), treated two fetuses with EXIT-to-resection of SCT, one of whom survived[14] ; the toher died of necrotizing enterocolitis and sepsis. One additional case was reported by surgeons at Zhejiang University (China), with favorable outcomes for both the fetus and the mother at 18-month follow-up.[64]

Benefits of the EXIT procedure include the following[64] :

• Direct ligation of the tumoral blood supply
• Absence of need to obtain or secure a fetal airway before resection
• Ability of the placenta can compensate for fetal blood loss during resection

Risks of the EXIT procedure include the following[64] :

• Potential for increased maternal blood loss due to relaxation of the uterus (decreased with the use of uterine staplers for hysterotomy)
• Risk of maternal infection
• Prolonged postpartum recovery time

Several centers have described salvage of hydropic fetuses with SCT with open fetal resection. However, preterm labor remains the Achilles heel of fetal surgery. To circumvent preterm labor and to decrease maternal morbidity associated with fetal intervention for SCT, minimally invasive techniques such as percutaneous cyst aspiration for cystic SCTs and radiofrequency (RF) ablation (RFA) for solid SCTs, have been developed.[65, 66]

The RFA technique employs US guidance to target the vessels feeding the SCT and thereby reduce tumor vascularity. An eight-prong LeVeen RF probe is deployed through a 15-gauge needle into an umbrellalike configuration to a diameter of 20-35 mm.[65]  The probe delivers energy in a spherical volume to cause tissue and tumor necrosis.

RFA for SCT has been controversial. The potential risks of this procedure include gas embolization due to microbubbles, hyperkalemia caused by tissue necrosis, perineal damage, hemorrhage, preterm labor, and fetal demise.[66]

In a report of four fetuses with SCT, RFA successfully reduced tumor vascularity in all cases[65] ; however, intrauterine fetal demise due to hemorrhage into the tumor occurred in one case, and another fetus underwent termination after postoperative magnetic resonance imaging (MRI) showed fetal brain damage. The two remaining fetuses survived but had evidence of perineal damage at birth.

Lam et al reported using RFA to treat an SCT in an 18-week-old fetus, but the fetus died 2 days after the procedure.[67]  Ibrahim et al reported a fetus born with sciatic nerve injury and malformation of the acetabulum and femoral head after RFA treatment for SCT.[68]  A study from Korea reported six cases of fetal SCT treated with RFA; five of the six patients survived, and one patient had a left-leg palsy and fecal and urinary incontinence.[29]

In summary, although RFA has been used as salvage therapy in fetuses who would have otherwise died, many of these patients were born with complications. The keys to successful treatment with RFA may be (1) limiting the extent of coagulation in any single attempt to prevent massive hemorrhage or perineal necrosis and (2) performing a series of limited ablations.[65, 67]  RFA as a treatment modality for fetal SCT remains limited and problematic, and more studies are necessary to determine whether and how this technique should be used.

Laser ablation for SCT was first described in 1996 at 20 weeks' gestation.[69] The pregnancy was complicated by polyhydramnios but not by placentomegaly or hydrops. Two unsuccessful attempts were made at 20 and 26 weeks' gestation to ablate the main vessels feeding the SCT, but the infant survived.

In this technique, local anesthesia is infiltrated into the skin and subcutaneous tissues.[31] Cordocentesis is performed to deliver fetal anesthesia with fentanyl (15 µg/kg) and pancuronium (2 mg/kg).[31] This can also be delivered to the fetus IM. Under US guidance, a 1.9-mm 60° fetoscope is introduced into the amniotic cavity percutaneously through a sheath, and a 0.4 mm neodymium-doped yttrium-aluminum-garnet (Nd:YAG) laser fiber is used to coagulate the vessels.[69]

In a retrospective study of 12 patients undergoing fetal intervention for SCT, four patients underwent laser ablation, but only one survived.[30] In a case report, a 24-week-old hydropic fetus underwent percutaneous laser ablation for SCT but died 2 days after fetal intervention.[31] In another study, a 22-week-old fetus underwent percutaneous laser ablation of tumor vessels and survived.

Another retrospective multicenter study identified five fetuses who underwent minimally invasive fetal intervention for hydrops or cardiac insufficiency as a result of SCT.[55] Four of these five fetuses underwent laser ablation, and three of them were targeted vascular ablations. Survival for the fetuses who underwent fetal intervention was 40%, but many patients required multiple procedures because of the recurrence of hydrops, cardiac insufficiency, or both.

Systematic review of laser ablation for SCT showed that ablation caused cessation of tumoral blood flow in 36.4% of cases but led to preterm premature rupture of membranes (PROM) in 18.2% of cases and preterm labor in 87.5% of cases.[70]

In contrast to laser ablation of the vascular inflow to the tumor, a retrospective single-center study out of Poland described percutaneous intratumor laser ablation in seven fetuses with large solid SCTs.[71]  Three patients survived to delivery and underwent surgical excision, three survived to delivery but died before undergoing surgical resection, and one died in utero.[71]

Laser ablation for SCT, like RFA for SCT, represents the movement in fetal surgery toward minimally invasive techniques. However, the outcomes vary, and current experience is too limited to determine whether laser ablation will be effective in reducing mortality in fetuses with SCT.

Alternative minimally invasive techniques for ligating the tumoral vascular supply are currently being developed, such as the smart shape-memory polymeric string,[72] but outcomes from preclinical studies have not yet been reported.

After the operative procedure, 6 g of magnesium sulfate is given IV as a loading dose, and a continuous infusion is maintained for tocolysis. An epidural infusion also prevents uterine irritability, and indomethacin rectal suppositories are given every 6 hours for tocolysis. Approximately 18-24 hours after the procedure, the mother is transitioned from a magnesium drip to oral nifedipine for tocolysis. A single dose of maternal betamethasone is given in anticipation of preterm delivery.[28]

Postoperatively, the fetus undergoes daily echocardiography and US to assess for ductal constriction, fetal movement, amniotic separation, and volume of amniotic fluid.