Depending on the diagnosis, therapeutic treatments – known as fetal therapy – can be performed, with the objective of achieving fetal well-being. These treatments include medical and surgical procedures, such as fetoscopic selective laser photocoagulation, cordocentesis, and radiofrequency ablation.

Fetoscopic Selective Laser Photocoagulation (SLP)

Definition

Fetoscopic selective laser photocoagulation (SLP) is used for the treatment of early-onset, advanced-stage Twin-Twin Transfusion Syndrome (TTTS). With this procedure, a fetoscope (an elongated surgical camera) is inserted into the uterus under anesthesia, enabling visualization of the placenta and twin circulations. Fetoscopy allows for identification of disease-causing blood vessel communications (known as anastomoses) between twin blood supplies. Using laser energy, blood flow within these anastomoses can be stopped, thereby interrupting the exchange of blood that is involved in TTTS.

Why It’s Done

TTTS affects approximately 15% of monochorionic, diamniotic twin pregnancies. Untreated severe TTTS is associated with a nearly 90% mortality rate and a 15-50% risk of neurological morbidity among survivors. SLP is the optimal form of therapy for early-onset, advanced stage TTTS presenting prior to 26 weeks gestational age, and is associated with improvements in overall survival, survival of at least one twin, and overall neurological outcomes.

Risks

Pregnancies undergoing SLP are at increased risk for early complications such as preterm premature rupture of membranes (PPROM), early pregnancy loss, infection, bleeding, and preterm delivery. There is a risk that one or both twins might not survive the procedure, and a twin death can have serious health consequences upon a surviving co-twin. Late complications of therapy may include intrauterine growth restriction, premature delivery, and various recurrent forms of transfusion between twins.

Before Therapy

At Columbia University Medical Center, SLP is generally offered between 18 and 26 weeks gestational age. Prior to the procedure, a comprehensive ultrasound is performed to confirm the complicated twin diagnosis and whether or not the pregnancy might benefit from therapy. Other diagnostic tests might also be offered around this time, including a fetal echocardiogram. Prior to therapy, a consultation with a high-risk obstetrician (MFM doctor, or perinatologist) experienced with SLP takes place, at which time the procedure is discussed in detail. This conversation will include a detailed explanation of risks and benefits of therapy, as well as alternative options that might be considered.

Results:

In the Eurofetus randomized trial of SLP versus amnioreduction (needle-based fluid reduction to treat TTTS), SLP was associated with survival of at least one twin in 76% of cases and neurologically intact survival at 6 months of age in 76% of cases, compared to 56% and 51% respectively with amnioreduction. Cystic periventricular leukomalacia (a serious form of brain injury) was also decreased in infants following SLP (6% versus 14% with amnioreduction). Published series studying long-term neurological outcomes among survivors of SLP indicate that approximately 82-94% of laser survivors are free of major neurological disabilities.

Fetal Shunts

Definition

Fetal shunts provide continuous drainage of abnormal fluid accumulations within certain fetal body spaces. They consist of flexible plastic catheters that are percutaneously (through the mother’s skin) guided into an in utero fetal location under continuous ultrasound guidance.

Why It’s Done

The two most commonly placed shunt types include vesicoamniotic shunts for lower urinary tract obstruction (LUTO, or fetal bladder obstruction) and thoracoamniotic shunts for severe fetal hydrothorax (fluid in chest) or certain forms of Congenital Pulmonary Airway Malformation (CPAM).

In the case of LUTO, an over-distended urinary bladder and highly pressurized urinary backup place the pregnancy at high risk for renal (kidney) insufficiency or failure, as well as multiple other problems including ureteral and bladder dysfunction. Long-standing severe decreases in amniotic fluid volume usually occur as a result of this blockage, subjecting the fetus to pulmonary hypoplasia that can greatly limit or altogether prevent survival after birth. By allowing for communication between the bladder and the amniotic space, vesicoamniotic shunt placement decompresses the bladder – theoretically preventing further renal damage – and by doing so reconstitutes the amniotic space, allowing for pulmonary development with sufficiently early intervention. Although this strategy cannot reverse renal injury that has already occurred, it may reduce risk for further injury.

Connecting the chest cavity to the amniotic space, thoracoamniotic shunt placement is generally reserved for severe antenatal hydrothorax. In appropriate cases, shunt placement decompresses the fluid collection around the lungs, allowing for pulmonary (lung) expansion within the thoracic (chest) cavity, which may promote pulmonary development. By reducing intrathoracic pressure, shunt-facilitated continuous drainage may also increase venous return to the fetal heart and improve overall hemodynamic performance.

Risks

Procedural risks include preterm premature rupture of amniotic membranes (PPROM), bleeding, infection, loss of the entire pregnancy, preterm labor, and premature delivery. There is also a rare risk of traumatic fetal injury that can involve bleeding.

As shunts are narrow, flexible plastic catheters, they are at high risk to become blocked, dislodged, otherwise nonfunctional, which may indicate repeat shunt placement. Additionally, severe hydrothorax cases often require bilateral shunt placements.

Before Therapy

Prior to the procedure, a comprehensive ultrasound is performed to confirm the complicated diagnosis and that the pregnancy might possibly benefit from therapy. A consultation with a high-risk obstetrician (MFM doctor, or perinatologist) experienced with shunt placement takes place, at which time the procedure is discussed in detail. This conversation will include a detailed explanation of risks and benefits of therapy, as well as alternative options that might be considered. Other diagnostic tests might also be offered around this time, including genetic amniocentesis and a fetal echocardiogram.

Prior to vesicoamniotic shunt therapy, a series of up to three ultrasound-based bladder samplings (vesicocenteses) using an amniocentesis needle may be performed. The goal of these studies is to analyze the fetal urine and determine if there appears to be some preserved kidney function. These results can help to determine if a pregnancy is a suitable candidate for therapy.

Prior to thoracoamniotic shunt therapy for a severe hydrothorax, one or two ultrasound-based drainages of the abnormal chest fluid (throacocenteses) are usually performed. These are both diagnostic (enabling analysis of the drained fluid) and also occasionally therapeutic, as some cases remain decompressed (do not recur) after thoracocentesis drainage.

Results:

Whereas vesicoamniotic shunt placement can promote survival that likely would not have been possible without therapy, survivors are at long-term risk of renal failure, renal insufficiency, dialysis requirement, kidney transplantation, bladder and ureteral dysfunction, repeat hospitalizations, recurrent infections, sexual dysfunction, and pulmonary issues, among other problems.

Thoracoamniotic shunt placement is believed to improve newborn survival chances. In some cases, hydrothorax can persist after birth, leading to short- and long-term health care issues for affected children. Sometimes underlying genetic syndromes or other physical malformations are noted during pregnancy or after delivery, and this can worsen outcomes.

Cordocentesis

Definition

Cordocentesis refers to the ultrasound-based guidance of an amniocentesis needle into the umbilical vein, which is a main blood vessel within the umbilical cord of a pregnancy. Cordocentesis is also referred to as PUBS, or Percutaneous Umbilical Blood Sampling.

Why It’s Done

Cordocentesis can be performed for diagnostic and therapeutic purposes. Common diagnostic uses include assessing for fetal anemia, evaluating for fetal thrombocytopenia (low platelet count), and occasionally for genetic testing. The most common therapeutic use for cordocentesis involves the transfusion of red blood cells as treatment for severe fetal anemia.

Risks

Procedural risks include preterm premature rupture of amniotic membranes (PPROM), bleeding, infection, loss of the entire pregnancy, preterm labor, and premature delivery. There is a rare risk on the order of about 1% of a cord accident (injury to an umbilical vessel) that can result in severe fetal bleeding, changes in the fetal heart rate, fetal injury or death, and – at more advanced gestational ages – emergency cesarean delivery.

Before Therapy

At Columbia University Medical Center, cordocentesis generally may be offered at and beyond 18 weeks of gestation, as indicated. Prior to the procedure, a comprehensive ultrasound is performed to confirm that the pregnancy might benefit from cordocentesis. Prior to therapy, a consultation with a high-risk obstetrician (MFM doctor) experienced with cordocentesis takes place, at which time the procedure is discussed in detail. This conversation will include a detailed explanation of risks and benefits of therapy, as well as alternative options that might be considered.

Results:

Cordocentesis is usually well-tolerated. Pregnancy outcomes following cordocentesis are related to the underlying cause for the procedure, including the fetal condition around the time of therapy.

Radiofrequency Ablation (RFA)

Definition

Radiofrequency ablation (RFA) causes thermal (heat-related) injury to tissues using high-frequency radiowaves. When applied to the umbilical cord of an abnormal twin, RFA can be used to immediately stop blood flow within it. This leads to an intentional demise (loss) of the abnormal twin, while also decreasing risk of permanent neurological (brain) injury or death for a co-twin.

Why It’s Done

Complicated monochorionic (single-placenta) twin pregnancies can pose particular challenges due to the implications of a shared twin placental circulation – problems affecting one twin can directly risk the health of the other. In monochorionic twin pregnancies, where an abnormality is detected that places one or both twins at increased risk of death in utero or severe morbidity, selective fetal reduction (termination) by RFA can be considered in an attempt to maximize the outcome for the surviving twin.

Risks

Procedural risks include preterm premature rupture of amniotic membranes (PPROM), bleeding, infection, loss of the entire pregnancy, preterm labor, and premature delivery. There is a risk that both twins might not survive the procedure, and a rare risk of thermal injury to the non-targeted twin. Long-term results, including neurological outcomes for RFA survivors, are limited, but appear to be favorable. While RFA is considered to be safe for the pregnant mother, uncommon but potentially serious injuries include thermal injuries and procedure-related bleeding.

Before Therapy

At Columbia University Medical Center, RFA therapy is ideally offered between 18 0/7 and 23 6/7 weeks gestational age. Prior to the procedure, a comprehensive ultrasound is performed to confirm the complicated twin diagnosis and whether or not the pregnancy might benefit from therapy. Other diagnostic tests might also be offered around this time if indicated, such as fetal echocardiography and diagnostic amniocentesis. Prior to therapy, a consultation with a high-risk obstetrician (MFM doctor, or perinatologist) experienced with the use of RFA in pregnancy takes place, at which time the procedure is discussed in detail. This conversation will include a detailed explanation of risks and benefits of therapy, as well as alternative options that might be considered.

Results:

Although success rates for selective fetal reduction using RFA are difficult to determine, available series suggest a 70-80% survival for the co-twin.