Fetal anemia can occur secondary to maternal alloimmunization, viral infections, homozygous thalassemia, maternal-fetal hemorrhage, and placental chorioangioma. The rate of fetal anemia secondary to rhesus D (RhD) sensitization has decreased to 1 in 500 pregnancies following the use of RhD immunoglobulin prophylaxis. Serial Doppler studies of the middle cerebral artery (MCA) peak velocity are used to diagnose fetal anemia. A sample of fetal umbilical cord blood just before starting the intrauterine transfusion (IUT) allows accurate assessment of fetal anemia.

IUTs are frequently performed using a 20- or 22-gauge needle with local anesthesia at the maternal needle insertion site. The needle is inserted percutaneously through the maternal abdomen and uterus under ultrasonographic guidance to access the umbilical vein ( Fig. 7.1 ). The umbilical cord is often accessed near its placental insertion for stability, but a loop of umbilical cord or an intrahepatic portion of the umbilical vein can also be used. Before 18 weeks’ gestation, intraperitoneal transfusion may be chosen for treatment of fetal anemia given that accessing the umbilical vein may not be possible.

Percutaneous Intrauterine Umbilical Cord Sampling and Transfusion.

Illustration from University of California, San Francisco Fetal Treatment Center, San Francisco, CA.

The transfused volume of O-negative, cytomegalovirus (CMV)-negative, irradiated, leukocyte-depleted, packed red blood cells is determined based on the estimated fetal weight, gestational age, autologous hemoglobin, and hemoglobin of the sampled fetal blood. Fetal hemoglobin level increases, then slowly decreases, so multiple IUTs are often required at 1- to 3-week intervals. Administration of a muscle relaxant to the fetus should be considered to decrease the chance of fetal movement dislodging the transfusion needle or shearing the cord vasculature. The umbilical cord does not have pain receptors, but if the needle is advanced into the fetal abdomen for intraperitoneal access, fentanyl or another opioid should be administered to the fetus to blunt the stress response that results. Providers should be prepared for a possible emergency cesarean delivery if the fetus is of viable age. The rate of fetal demise following IUT is approximately 3%.

Lower urinary tract obstruction (LUTO) occurs in approximately 1 in 4000 live births. Congenital bilateral hydronephrosis results from fetal urethral obstruction at the bladder outlet, most commonly by either posterior urethral valves (PUVs, typically male fetuses) or urethral atresia. Other causes of fetal obstructive uropathy include obstruction at the ureteropelvic or vesicoureteric junction and a number of complex disorders in females (e.g., cloacal plate anomalies). LUTO may lead to progressive renal dysplasia and dysfunction, bladder distention, and oligohydramnios, and ultimately result in devastating developmental consequences, such as limb and facial deformities, pulmonary hypoplasia, and even neonatal death ( Fig. 7.2 ). Although postnatal correction relieves the obstruction, 25% to 30% of survivors develop end-stage kidney disease requiring dialysis by 5 years of age. Early intrauterine intervention with placement of a vesicoamniotic shunt (VAS) allows drainage of urine from the fetal bladder into the amniotic cavity, and in animal models, improves dysplastic renal histology, restores normal urine flow and amniotic fluid volume, and results in improved lung growth and development.

Developmental Consequences of Fetal Urethral Obstruction. Obstructed fetal urinary flow results in hydronephrosis, hydroureter, megacystis, oligohydramnios, and pulmonary hypoplasia.

Redrawn from Harrison MR, Filly RA, Parer JT, et al. Management of the fetus with a urinary tract malformation. JAMA . 1981;246:635–639.

A VAS is a valveless, double-coiled catheter placed percutaneously with ultrasonographic guidance, with one coil in the urinary bladder and the other in the amniotic space. Common catheter-associated problems include: (1) difficult placement, occlusion, and displacement; (2) fetal trauma, iatrogenic abdominal wall defects, and amnioperitoneal leaking; and (3) preterm PROM, preterm labor, and chorioamnionitis. In a 2017 metaanalysis of primarily cohort studies, there was a perinatal survival improvement with VAS compared with conservative management (57.1% versus 38.8%, P <.01) but no difference in 2-year survival or postnatal renal function.

Fetal cystoscopy is a more recent treatment in which a trocar-assisted fetoscope enters the fetal bladder under ultrasonographic guidance and allows direct visualization of the fetal urethra. Although not a viable treatment for urethral atresia, fetal cystoscopy facilitates diagnosis and treatment of LUTO caused by PUVs. Once visualized, the PUVs are destroyed using guidewires and hydroablation or laser ablation. A two-center case-control study showed that both fetal cystoscopy and VAS improved the 6-month survival rate compared with no intervention in severe LUTO.

A recent multicenter prospective clinical trial that examined the use of serial amnioinfusions (1 to 3 times each week) in fetuses with bilateral renal agenesis found that therapy mitigated lethal pulmonary hypoplasia, but was associated with higher preterm delivery and a low rate (35%) of survival to hospital discharge and long-term dialysis ; the survival rate was lower than anticipated in neonates born with renal failure (but not restricted to bilateral renal agenesis). The trial was stopped early owing to concerns about neonatal morbidity and mortality despite demonstration of the intervention’s efficacy. Current evidence supports the use of fetal intervention for LUTO in selected fetuses in an effort to restore amniotic fluid volume, prevent pulmonary hypoplasia, and decrease perinatal mortality.

Congenital diaphragmatic hernia (CDH) occurs in approximately 1 in 2500 live-born infants and can cause significant morbidity and mortality from pulmonary hypoplasia and insufficiency. Survival rates have improved to greater than 70% over the past 25 years and are closely associated with the degree of pulmonary hypertension and respiratory insufficiency. Significant morbidity occurs, despite optimal postnatal surgical management at tertiary care medical centers. Intrauterine intervention has the potential to decrease pulmonary hypoplasia and improve fetal lung development before delivery. Fetal lamb models of CDH demonstrated that parenchymal hypoplasia and associated pulmonary vascular changes could be reversed by correction in utero . Primary open repairs of human CDH in utero have been undertaken with limited success.

Tracheal occlusion impedes the normal egress of fetal lung fluid and results in expansion of the hypoplastic lung, thereby inducing lung growth, cellular maturation, and movement of the viscera out of the thorax in fetuses with CDH. Once the trachea is occluded, fetal pulmonary fluid slowly accumulates and expands the lung, pushing the viscera out of the thorax. A small detachable balloon for endoluminal tracheal occlusion is placed in the trachea via percutaneous endoscopic endotracheal intubation and is left in place ( Fig. 7.3 ). Because of concern for tracheal damage by very early tracheal balloon placement, the small detachable tracheal balloon is often placed via percutaneous endoscopic endotracheal intubation between 26 and 28 weeks’ gestation and removed before birth by a second fetoscopic procedure near 34 weeks’ gestation (if the fetus is still in utero ). This second procedure is performed to minimize the risk for preterm labor, avoid the need for the EXIT procedure, and possibly improve lung growth and minimize the reduction of type II alveolar cells associated with prolonged tracheal occlusion. If the balloon is still in place and delivery appears imminent, it must be removed or deflated prior to or at the time of delivery.

Fetal Tracheal Occlusion Using a Balloon.

From Harrison MR, Albanese CT, Hawgood SB, et al. Fetoscopic temporary tracheal occlusion by means of detachable balloon for congenital diaphragmatic hernia. Am J Obstet Gynecol . 2001;185:730–733.

In 2021 two multicenter randomized Tracheal Occlusion To Accelerate Lung growth trials were published. These trials compared postnatal CDH management with both late (30 to 32 weeks’ gestation) fetoscopic endoluminal tracheal occlusion (FETO) intervention for moderate lung hypoplasia and earlier FETO intervention (27 to 30 weeks’ gestation) for severe lung hypoplasia. In both trials, the fetal tracheal balloon was removed in the 34th week of gestation. Compared with postnatal intervention, there was increased survival to discharge and to 6 months in fetuses with severe CDH treated in utero (40% versus 15%, P =.009). The increased survival benefit was not statistically significant in the fetuses with moderate CDH that underwent in utero intervention compared with the postnatal group (survival to hospital discharge 63% vesus 50%, P =.06). In both trials the fetal tracheal occlusion procedure resulted in higher rates of preterm PROM and preterm birth. Although promising, additional long-term follow-up in these patients is needed to better understand the efficacy of this intervention for CDH.

Congenital pulmonary airway malformations (CPAMs) are pulmonary tumors with cystic and solid components usually isolated in a single lung. The incidence is approximately 1 in 25,000 pregnancies. Lesions are assessed by ultrasonography and can be classified as either macrocystic (≥5 mm diameter) or microcystic (<5 mm diameter). Lesions can regress, resulting in minimal associated morbidity, or progressively enlarge, often resulting in fetal hydrops (fetal heart failure). The size and growth of the lesions, rather than their specific type, are the primary determinants of overall prognosis. Small lesions detected in utero or in the neonate are treated after birth by surgical excision of the affected pulmonary lobe. Large lesions can cause mediastinal shift, hydrops, polyhydramnios, and pulmonary hypoplasia and can interfere with fetal or neonatal survival. In a retrospective single-institution review of 71 cases, the initial antenatal ultrasonographic ratio of CPAM volume-to-fetal head circumference (CPAM volume ratio [CVR]) was evaluated for hydrops formation and postnatal outcomes. Fetuses with a CVR < 0.56 were noted to have no adverse postnatal outcomes, whereas a CVR > 0.56 had a positive predictive value for adverse postnatal outcomes of 33%. In addition, a CVR > 1.6 was associated with a greater risk for hydrops, and a CVR ≤ 1.6 with absence of a dominant cyst was associated with a less than 3% risk for hydrops.

Depending on size, location, and other characteristics, CPAMs can be managed with either fetal intervention or postnatal resection. Macrocystic lesions can be decompressed in utero by thoracocentesis or placement of shunt catheters between the cystic area and the amniotic cavity, resulting in sustained decompression and resolution of hydrops. These in utero procedures are followed by postnatal surgery. However, not all lesions can be decompressed successfully with a shunt because the cysts are not always contiguous (i.e., in communication with each other) and can refill rapidly. In addition, thoracoamniotic shunts have associated risks, including malfunction, displacement, fetal hemorrhage, preterm PROM, preterm labor, and chorioamnionitis. In a series of 68 fetuses with macrocystic CPAMs treated with thoracoamniotic shunts, the overall survival rate was 68% in hydropic and 88% in nonhydropic fetuses. A 2023 single institution retrospective review of 31 fetuses that underwent thoracoamniotic shunts for congenital lung malformations found long-term complications in 60% of the 15 surviving children (median age 11 years), including chest wall deformities and one phrenic nerve injury. There was otherwise normal lung function without limitation in 14 of the 15 surviving children.

CPAMs inappropriate for drainage can be resected with open fetal surgery. Intrauterine pulmonary lobectomy for lesions associated with fetal hydrops has resulted in a 30-day postnatal survival rate of 50%, with tumor resection allowing for compensatory lung growth and resolution of hydrops. Other less common options for fetal intervention include resection while on placental circulation (EXIT procedure), radiofrequency or laser ablation, and percutaneous ultrasound-guided sclerotherapy. Maternal administration of betamethasone has been noted to improve fetal hydrops and overall outcome in selected fetuses with CPAM.

Sacrococcygeal teratoma (SCT) has an incidence of approximately 1 to 2 in 20,000 pregnancies and is associated with perinatal demise in 25% to 37% of cases. Management requires serial ultrasonographic assessments, as some undergo rapid, substantial growth (e.g., volume 500 to 1000 cm ³ ) ; function as large arteriovenous (AV) fistulas; and result in high-output cardiac failure, hydrops fetalis, and placentomegaly. SCTs are staged using the Altman criteria , which focus on their location. Stage I tumors are based entirely outside the pelvis and are suitable for intervention; by contrast, Stage IV tumors are completely within the pelvis and are not amenable to fetal resection. Tumor size is estimated based on a tumor volume-to-fetal weight ratio; large SCTs > 0.1 cm ³ /g (prior to 24 weeks’ gestation) and those with rapid growth (>150 cm ³ /week) are associated with adverse outcomes, including tumor rupture and hemorrhage, as well as intrapartum dystocia. Current surgical techniques do not allow complete resection of lesions that deeply invade the pelvis; however, in utero radiofrequency ablation, embolization, and thermocoagulation of the tumor or blood supply can reduce the tumor burden and resolve hydrops. Large multicenter studies are needed to determine which therapies deliver the most definitive, optimal benefits ( Fig. 7.4A ). During open fetal tumor resection ( Fig. 7.4B ), catheterization of a fetal limb or umbilical cord vein is required to allow fetal blood or fluid administration.

In Utero Fetal Treatment of Sacrococcygeal Teratoma (SCT). (A) Radiofrequency ablation treatment of an SCT. (B) Open fetal surgery for in utero vascular ablation and tumor resection of SCT. Note pulse oximeter on fetal foot, placement of rectal temperature probe, and use of ultrasonography to monitor blood flow in SCT.

(A) From Van Mieghem T, Al-Ibrahim A, Deprest J, et al. Minimally invasive therapy for fetal sacrococcygeal teratoma: case series and systematic review of the literature. Ultrasound Obstet Gynecol . 2014;43:611–619. (B) Illustration from author Mark Rollins during his affiliation with the UCSF Fetal Treatment Center, San Francisco, CA.

Some SCT cases are accompanied by “ maternal mirror” or Ballantyne syndrome , a hyperdynamic state (i.e., hypertension, peripheral and pulmonary edema) in which the maternal physiology mimics the abnormal circulatory physiology of the hydropic fetus. This syndrome is associated with a substantial increase in fetal mortality and maternal morbidity and requires aggressive management similar to that used for preeclampsia with severe features, a disease from which it must be distinguished. Platelet count, aspartate aminotransferase, alanine aminotransferase, and haptoglobin are typically unaffected in maternal mirror syndrome and may serve as diagnostic clues. Unfortunately, maternal mirror syndrome does not resolve quickly, even with rapid correction of the fetal pathophysiology, and severe life-threatening maternal complications including pulmonary edema occur in about 20% of cases.

NTDs are characterized by a failure of neural tube fusion during development at the cranial level ( anencephaly ), spinal level ( spina bifida ), or both ( craniorachischisis ). There is wide heterogeneity in the birth prevalence of spina bifida, with rates of 3.4 to 3.7 per 10,000 births in most upper-middle-income and high-income countries versus rates that are 2- to 10-fold higher in world regions without folic acid fortification programs. In contrast to anencephaly and craniorachischisis, spina bifida is not a lethal condition even in the most severe forms, such as myeloschisis or myelomeningocele (MMC) . In open MMCs, the spinous processes and overlying muscles and skin do not form normally, leading to exposure of the meninges and neural tissue. The exposed nerves can become inflamed and injured during the pregnancy from direct pressure as the fetus moves in utero and from amniotic fluid which becomes toxic to nerves in the third trimester ( Fig. 7.5A ).

Myelomeningocele. (A) Spine with myelomeningocele. (B) Diagram demonstrating release of placode from arachnoid membrane. (C) Myelomeningocele repair during open in utero fetal surgery. Note the cystic membrane covering the deficit has been incised and meninges are visible inside the cystic cavity. The absorbable copolymer staples used during creation of the hysterotomy are visible along the uterine edges. CSF , Cerebrospinal fluid.

(A) Modified from Kerr LM, Huether SE. Alterations of neurologic function in children. In: McCance KL, Huether SE, Brashers VL, Rote NS, eds. Pathophysiology: The Biologic Basis for Disease in Adults and Children , 7th ed. Elsevier; 2014:660–688. (B) Image created by Katherine Relyea, MS, CMI, and printed with permission from Baylor College of Medicine. (C) Illustration from author Mark Rollins during his affiliation with the UCSF Fetal Treatment Center, San Francisco, CA.

The morbidity associated with spina bifida varies depending on the severity of the associated neuronal migrational abnormalities, known collectively as the Chiari II malformation , and the spinal level of the lesion. Patients can have paraparesis or paraplegia, neurogenic bowel and bladder, hydrocephalus, neuromuscular scoliosis, cranial nerve palsies, and neurocognitive deficits.

Outcomes from prenatal repair of MMCs in animal models support a “two-hit” hypothesis in which the pathology is produced by both failure of the fetal neural tube to close, combined with prolonged exposure to the amniotic fluid. The aim of fetal surgery is to reduce the damage that occurs in utero by creating a water-tight repair, thereby protecting the spinal cord and nerves from exposure to the amniotic fluid during the remaining gestation.

If the defect is not repaired in utero , surgical closure is generally performed within 72 hours after birth to prevent infection and preserve existing neurologic function. With postnatal NTD repair, hydrocephalus occurs in nearly all neonates with thoracic level lesions, approximately 85% of lumbar level lesions, and approximately 70% of sacral lesions. Learning disabilities and cognitive defects are associated with the Chiari malformation, hydrocephalus, and damage to the white matter. Despite treatment, permanent neurologic deficits such as central hypoventilation, vocal cord dysfunction, and oromotor and swallowing dysfunction can still occur in a minority (approximately 5%) of patients from underlying brainstem dysplasia associated with the Chiari II malformation. In addition, lifelong complications also include fecal incontinence (77%) and urinary incontinence with 54% requiring regular catheterization. Orthopedic deformities such as clubbed feet, scoliosis, hip dislocation, and lower-extremity weakness are also common.

Prenatal MMC repair is similar to a postnatal repair, but some modifications are necessary with fetal tissue. The first step in both procedures involves releasing the spinal cord from the skin by cutting the arachnoid membrane between the placode and the junctional zone ( Fig. 7.5B ). Next, dura can be closed over the spinal cord but it is frequently very thin and fragile in a fetus and not water-tight; this layer can be augmented with myofascial flaps, followed by the closure of the skin. Multiple surgical techniques exist to close the defect when there is not enough skin, including sewing in a patch, bipedicular advancement flaps, and rotational flaps. The common goal of all these procedures is to achieve a water-tight closure to prevent exposure to amniotic fluid and further cerebrospinal fluid leakage ( Fig. 7.5C ).

A randomized, prospective, multicenter clinical trial (the Management of Myelomeningocele Study [MOMS] trial) demonstrated that in utero repair improved motor function at 30 months of age and reduced the incidence of hydrocephalus. Closure of the defect before 26 weeks’ gestational age reverses hindbrain herniation. The MOMS-II trial evaluated the original MOMS cohort at school age. The hydrocephalus benefit persisted and fetal patients who required a shunt were less likely to need a ventriculoperitoneal shunt revision ( Table 7.2 ).

Open prenatal surgery portends the risk of uterine dehiscence. In 2019 the results from an international prospective observational registry of 77 subsequent pregnancies after open MMC repair demonstrated the risk of uterine rupture was 9.6%, with an additional risk of uterine dehiscence or thinning of 17.3%. Other less invasive techniques, ranging from fully percutaneous to a “hybrid” laparotomy-assisted fetoscopic approach, have been developed with the aim of allowing a vaginal delivery and decreasing maternal and obstetric risks while producing equivalent neurosurgical results equivalent to the open method. In 2021 the International Fetoscopic Myelomeningocele Repair Consortium reported the pregnancy and postnatal outcomes at 12 months in patients who underwent prenatal fetoscopic repair. The average gestational age at delivery was 34 weeks, similar to that reported for open prenatal repairs, despite a higher rate of prelabor PROM (54.6% versus 32% to 46%). Neurologic outcomes at 12 months of life were similar.

Intraoperative anesthetic management typically consists of a combination of general endotracheal anesthesia administered to the mother and direct intramuscular (IM) opioid and muscle relaxant administered to the fetus. To optimize operating conditions, significant uterine relaxation is required. In addition, intraoperative fetal monitoring is employed to detect early fetal compromise.

Up to one-third of twin pregnancies are monochorionic; these pregnancies are at risk for complications unique to monochoronic pregnancies, including twin-to-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence (TAPS), twin reverse arterial perfusion (TRAP), and conjoined twinning.

Some vascular anastomoses connect both fetal circulations in the shared placenta of almost all monochorionic twin pregnancies. In cases with a significant number of vascular anastomoses between the umbilical circulations, shared blood flow through the AV chorionic vessels can become unidirectional and imbalanced, resulting in TTTS.

Twin screening for TTTS starts by 16 weeks’ gestation, with recognition typically occurring before 26 weeks’ gestation. TTTS typically complicates about 10% of monochorionic diamniotic pregnancies, or about 1 per 5000 births in general. The twin serving as the recipient can develop polycythemia, polyuria, polyhydramnios, and hypertrophic cardiomyopathy; this twin is at risk for hydrops fetalis and fetal death. The twin serving as the donor is typically hypovolemic, growth restricted, and pressed against the endometrium in an oligohydramniotic sac (sometimes called the “stuck” twin). This twin is at risk for neonatal renal failure, tubular dysgenesis and dysfunction, and high cardiac output hydrops fetalis.

Typically, the diagnosis of TTTS requires the presence of (1) a monochorionic diamniotic pregnancy; (2) oligohydramnios, defined as a maximal vertical pocket (MVP) < 2 cm in one amniotic sac; and (3) polyhydramnios, defined as MVP > 8 cm in the other amniotic sac. The most commonly used staging system describing the severity of TTTS was published by Quintero and is displayed in Table 7.3 . Assessment of additional cardiac function parameters is predictive of outcome in the recipient twin. Although the donor twin typically has normal cardiac function, the recipient twin can develop ventricular hypertrophy, atrioventricular valve regurgitation, ventricular diastolic and systolic dysfunction, and right ventricular outflow tract obstruction.

Fetuses with TTTS are at risk for neurologic injury with white matter lesions and long-term disability, preterm PROM, and preterm delivery. The incidence of preterm birth and neonatal morbidity increases as the stage/severity of TTTS increases, and when intervention is performed at an early gestational age (<18 weeks) or with a short cervix. In terms of mortality, if TTTS remains at Stage I or resolves, the overall survival rate is about 85% ; however, if TTTS progresses, the overall mortality rate of one or both fetuses can increase to greater than 80% if untreated.

A variety of therapeutic management techniques have been used to treat TTTS: (1) amnioreduction, either as a one-time procedure or serially; (2) selective feticide; and (3) selective fetoscopic laser photocoagulation (SFLP) of the vascular anastomoses between the twins.

Amnioreduction can be performed any time after fusion of membranes (about 16 weeks’ gestation) and is hypothesized to reduce the risk for preterm labor and improve placental blood flow. In a retrospective review, amnioreduction resulted in an overall birth survival rate of 78%, with 65% of recipient twins and 55% of donor twins alive at 1 month of age.

Selective feticide is reserved for severe cases of TTTS or when there is a discordant fetal anomaly in one twin, with decreased overall chance of survival. In certain countries or regions, selective feticide may not be an option for some patients because of legal restrictions.

SFLP is routinely offered between 16 and 26 weeks’ gestation. The US Food and Drug Administration (FDA) exemption for fetoscopic intervention on TTTS only applies for this time frame. However, consensus from a recent Delphi study suggests that SFLP can be offered as early as 15 weeks and up to 28 weeks in selected cases. The laser used for SFLP is typically inserted through a fetoscope to allow visualization of the vascular anastomoses to be ablated. The fetoscope enters the maternal abdomen and uterus in a placenta-free zone through a small percutaneously inserted cannula that allows passage into the recipient twin’s amniotic sac ( Fig. 7.6 ). The fetoscope placement is guided by ultrasonography and ideally positioned at 90 degrees to the placental vascular surface. Although typically positioned supine, in some situations the patient position may be dictated by the limited availability of a suitable entry point (e.g., predominantly anterior placenta). In rare instances where no such “window” can be identified, a laparoscopic-assisted technique requiring the placement of two trocars for pneumoperitoneum and manipulation of the uterus may be used. After completion of the SFLP, an amnioreduction may be performed to decrease the risk for preterm labor.

In utero Fetoscopic Laser Ablation for Twin-to-Twin Transfusion Syndrome. Under ultrasound guidance, a fetoscope is inserted percutaneously into the recipient twin’s amniotic sac. Using both ultrasonographic guidance and fetoscopic visualization, intertwin vessels are identified and ablated with the laser.

From Graves CE, Harrison MR, Padilla BE. Minimally invasive fetal surgery. Clin Perinatol . 2017;44:729–751.

The optimal management of Quintero Stage I TTTS is unknown; a recent systematic review and metaanalysis of Stage I TTTS demonstrated similar rates of survival with expectant management and laser therapy and slightly higher rates with amnioreduction (84.9%, 86.7%, and 92.2%, respectively, for survival of at least one twin; 67.9%, 69.7%, and 80.8%, respectively, for dual survival). Approximately 30% of Quintero Stage I cases managed by amnioreduction or expectant management will ultimately progress to more severe stages. Additional symptoms such as maternal discomfort with increasing polyhydramnios or cervical shortening may also prompt SFLP treatment. SFLP is the treatment of choice for TTTS at Quintero Stages II to IV. A 2004 randomized multicenter trial demonstrated the benefits of SFLP compared with amnioreduction for treatment of severe TTTS diagnosed between 15 and 26 weeks’ gestation. Rates of at least one twin survival were significantly higher in the laser treatment group. In addition, neurologic outcomes were better in the SFLP group. Survival of at least one twin is higher for earlier stages (86.9% for Stage I and 85% in Stage II), but remains moderately high even in higher stages (81.5% in Stage III and 82.8% in Stage IV), compared with Stage V (54.6%).

The most common complications of SFLP are preterm PROM with subsequent preterm labor and delivery. Immediate perioperative concerns such as fetal bradycardia, inadvertent septostomy, bleeding from placental vessels, placental abruption, chorioamnionitis, and maternal pulmonary edema are rare. Maternal anesthesia is commonly managed with either neuraxial blockade or local anesthetic infiltration from skin to myometrium, with or without additional sedation. In the rare case where a laparoscopy-assisted technique is performed, general anesthesia may be required.

TAPS is a type of chronic unbalanced sharing between fetuses that results in anemia in the donor twin and polycythemia in the recipient twin. In contrast to the large anastomoses that characterize TTTS, TAPS is believed to be related to the slow transfusion of blood from the donor to the recipient across tiny AV anastomoses. This leads to discordant hemoglobin concentrations, with one twin displaying chronic anemia while the other has polycythemia. The diagnosis is made postnatally based on the findings of a difference in hemoglobin concentration > 8 g/dL between twins and either a reticulocyte count ratio > 1.7 or placental findings of small vascular anastomoses.

Screening for TAPS during pregnancy is performed using MCA Doppler measurements, looking at both velocities and discordance between the twins, but there is neither consensus about the optimal approach to surveillance nor determination of diagnostic accuracy. TAPS occurs spontaneously in up to 5% to 10% of monochorionic pregnancies, and can complicate up to 3% to 16% of TTTS cases after laser ablation. The outcome of TAPS is highly variable.

Management options for TAPS include expectant management, early delivery, fetoscopic laser photocoagulation, or IUT for the anemic twin with or without partial exchange transfusion of the polycythemic twin. The anesthetic management for these cases is similar to SFLP or IUT performed for other indications.

In monochorionic twins, one twin can perfuse the other by retrograde blood flow though arterial-to-arterial anastomoses. TRAP sequence affects 1% of monozygotic twins, 1 in 35,000 pregnancies, and 1 in 30 triplet pregnancies. Inadequate perfusion of the recipient twin via only retrograde anastomotic flow results in the development of a set of nonviable anomalies that include acardia and acephalus. The acardiac twin is not viable, but its presence puts the entire pregnancy at risk during gestation. The viable (“pump”) twin perfuses both itself and the acardiac twin and is at risk for high-output congestive heart failure, polyhydramnios, fetal growth restriction, preterm birth, and intrauterine fetal death if left untreated.

The goal of therapy is to stop the blood flow to the acardiac twin by targeting the acardiac twin’s umbilical cord or intraabdominal vessels. This can be accomplished using various techniques such as intrafetal laser coagulation, bipolar cord coagulation, and radiofrequency ablation. The procedures are typically guided by ultrasonography, and absence of flow to the nonviable acardiac twin is confirmed with Doppler imaging at the end of the procedure.

In the North American Fetal Therapy Network Registry, the reported overall pump-twin survival rate was 80.8% and the premature PROM rate was 17% after radiofrequency ablation, based on data from 98 patients from 22 institutions. A metaanalysis and review of the literature noted the survival rate of the pump twin was also approximately 80% for most techniques.

TRAP intervention procedures are typically performed with minimal sedation and either infiltration of local anesthesia at the ablation device insertion site or the administration of neuraxial anesthesia.

Indications for catheter-based fetal cardiac interventions include (1) aortic valvuloplasty with the goal of preventing the development of hypoplastic left heart syndrome, (2) atrial septoplasty and stenting for hypoplastic left heart syndrome with an intact or highly restrictive atrial septum (HLHS-IAS), and (3) pulmonary valvuloplasty to prevent the need for single ventricle palliation for severe pulmonary stenosis and pulmonary atresia with intact ventricular septum (PS+PA/IVS). Fetal pericardiocentesis has also been employed to drain pericardial effusions. Fetal intrapericardial teratomas have been successfully resected with in utero open fetal surgery or while on placental support during an EXIT procedure.

For in utero aortic valvuloplasty, an angioplasty balloon is placed over a percutaneously inserted guide wire ( Fig. 7.7 ), with technical success as high as 83%. A 2023 systematic review and metaanalysis found that fetal aortic valvuloplasty was successfully performed in 84% of patients with conversion to biventricular circulation rate in 33% and a mortality rate of 20%. The International Fetal Cardiac Intervention Registry (IFCIR) reported results of 108 patients from 15 centers over a 15-year period. Fetal death occurred during the procedure in 8.3% of cases; another 8.3% of fetal patients died within 48 hours. Intraprocedure complications included fetal bradycardia, pericardial effusion, pleural effusion, balloon rupture, and death.

Percutaneous Fetal Aortic Valvuloplasty for Evolving Hypoplastic Left Heart Syndrome. The needle is inserted percutaneously through the maternal abdomen and uterus, then enters the apex of the fetal heart in alignment with the left ventricular outflow tract. A guidewire and a coronary dilation balloon catheter are advanced through the aortic valve, which is then dilated.

From Van Mieghem T, Baud D, Devlieger R, et al. Minimally invasive fetal therapy. Best Pract Res Clin Obstet Gynaecol . 2012;26:711–725.

The goals of atrial septoplasty (atrial perforation or balloon dilation) or stent placement for HLHS-IAS are to improve neonatal stability at delivery by creating an unobstructed atrial septum, and to reverse/reduce chronic changes to the pulmonary vascular bed, with the potential subsequent benefits of improving neonatal survival. The IFCIR reported technical success in 77% of cases, with intraprocedure fetal death in 13% of cases. Survival to discharge after birth was poor at 35%, though when successful, fetal cardiac intervention was associated with neonatal stability at delivery and fewer cesarean deliveries.

Interventions are performed in PS+PA/IVS with the aim of improving growth of the tricuspid valve and right ventricle such that biventricular repair is possible and preventing or reversing hydrops in cases that have significant tricuspid regurgitation. The IFCIR has reported a technical success rate of 71%. Fetal complications occurred in over half of cases, including intraprocedure fetal death in 12% of cases and delayed fetal loss due to circular shunt from significant pulmonary insufficiency in an additional 3.4%. The most common other complications were pericardial effusion requiring drainage in 48% and bradycardia requiring treatment in 36% of cases.

Early descriptions of fetal cardiac intervention reported an approach involving a mini-laparotomy to facilitate fetal positioning; this was associated with improved technical success early in their experience, though all patients in this series underwent general anesthesia. More recently, anesthetic management of these cases often involves the use of maternal neuraxial anesthesia. Fetal anesthesia is administered via ultrasound-guided direct IM injection of anesthetic drugs.

Maternal complications during fetal cardiac interventions are rare; however, anesthesia providers must be prepared for fetal resuscitation in these cases, which may involve drainage of pericardial effusions, administration of medications, or transabdominal fetal chest compressions.