++
Fetoscopic surgery is now the most commonly employed fetal surgical
technique used in a range of indications.17 The
most common is twin-twin transfusion syndrome, which occurs exclusively
in monochorionic gestations affecting 10% to 15% of
monochorionic twin pregnancies and accounting for 17% of
all prenatal mortality in twins. While the cause of twin-twin transfusion
syndrome is not known, chorioangiopagus, the vascular connections between
the twins, that normally occurs in monochorionic pregnancies is
a necessary prerequisite for this disease of polyhydramnios in the “recipient” twin
and severe oligohydramnios in the “donor” twin.
In addition, the recipient twin (the twin receiving blood) develops
a hypertrophic cardiomyopathy. Selective fetoscopic laser photocoagulation
of vascular connections can arrest the progression of twin-twin
transfusion syndrome.18-20 Untreated, it is almost
uniformly fatal, but with selective fetoscopic laser photocoagulation,
survival rates of 70% to 77% have been reported
with up to 64% of pregnancies having both twins survive
and 92% of pregnancies having 1 or both fetuses survive.
Other treatments, such as amnioreduction, may be effective in 20% to
30% of patients. Ultrasound-guided radiofrequency intrafetal
umbilical cord ablation may be indicated as salvage therapy to protect
1 twin from the death of the cotwin.
++
Twin reversed arterial perfusion sequence is another highly lethal
anomaly in which vascular connections between a “pump” twin
and an acardiac acephalic twin result in polyhydramnios, preterm
labor, heart failure, and death in the pump twin. Intrafetal radiofrequency
ablation of the umbilical cord to the acardius results in 95% survival
of the “pump” twin in cases in which adverse pregnancy
outcome is anticipated.22
++
Tracheal occlusion can accelerate fetal lung growth. During lung
development, there is a net egress of tracheal fluid that can be
blocked by tracheal occlusion, resulting in increased intratracheal
pressure and accelerated lung growth. In a prospective randomized
trial of fetoscopic balloon tracheal occlusion, there was no difference
in survival in left congenital diaphragmatic hernia compared to
postnatal therapy in cases with lung-to-head-circumference ratio
(LHR) less than 1.4.9 The result was not surprising
given the favorable outcome of fetuses with LHR greater than 1.0,
and the majority of patients had LHR greater than 0.9. This fetoscopic
technique was tried for fetuses with congenital diaphragmatic hernia
with LHR less than 1.0 and liver herniation. Balloon tracheal occlusion
was reversed before delivery with 83% survival compared
to 11% survival with conventional postnatal care in European
neonatal centers.10,11 This therapy is currently
not available in the United States due to lack of an FDA-approved
detachable balloon device.
++
Fetoscopic surgery has been successfully used to treat amniotic
band syndrome. Amniotic bands may form as a result of amniocentesis
or spontaneously encircle a limb and result in a tourniquet like
effect with subsequent limb amputation or death if the band involves
the umbilical cord. Fetoscopic laser release of amniotic bands has
prevented not only limb amputation but death from cord accidents.
The limbs affected by amniotic bands may have abnormalities from
amniotic bands, even if released, that include a secondary form of
lymphedema or failure of the distal limb to grow.33
++
Congenital high airway obstruction syndrome results from complete
airway obstruction due to tracheal or laryngeal atresia. Up to one
third of fetuses with congenital high airway obstruction syndrome
will spontaneously perforate through the atresia into the larynx
or esophagus with resolution of hydrops.34 Several
patients have now undergone fetoscopic laser perforation of laryngeal
or tracheal atresia to allow hydrops to resolve.35 An
EXIT (ex utero intrapartum treatment)
procedure (discussed later in this chapter) is necessary for delivery
of these infants, but the resolution of hydrops can result in much
healthier newborns.
++
Bladder outlet obstruction due to posterior urethral valves results
in megacystic kidneys, oligohydramnios, and, if untreated, severe
renal dysplasia and death from pulmonary hypoplasia. This condition
has been treated by vesicoamniotic shunting or open vesicostomy (see
next section). Cases that present prior to 20 weeks’ gestation
may be candidates for fetoscopic/cystoscopic laser ablation
of the posterior urethral valves with restoration of amniotic fluid
volume. It is unknown if a better renal outcome will also be achieved
by this approach.16,36,37
++
The indications for open fetal surgery remain relatively few,
and rarely do these conditions require this form of fetal intervention.
As mentioned earlier, steroids can to be effective in reversing
nonimmune hydrops in congenital pulmonary airway malformations (CPAM).
Steroid refractory CPAM with progression of hydrops, however, remains
an indication for open fetal surgery.5,6,29 The maternal
risks with open fetal surgery are higher than with fetoscopic intervention
because of the large laparotomy incision, the hysterotomy, and the
aggressive tocolytic regimen required for management. With the notable
exception of myelomeningocele, open fetal surgery may be indicated
for cases in which the life of the fetus is jeopardized. In open
fetal surgery for CPAM, a thoracoabdominal incision is used for
exposure, and care is taken to preserve even the tiniest of compressed
remaining hypoplastic lobe, as CPAM is usually lobar. The fetal
survival rate following an open fetal surgery for hydropic CPAM
is 60%. However, many losses occur when patients are referred
late in the course of the disease with end-stage nonimmune hydrops.
Those fetuses that are followed closely and show progression to
hydrops despite steroid administration are better risk candidates
if the surgery is performed earlier in the course of the disease.
++
Sacrococcygeal teratoma is a rare condition that occurs in only
1 of 25,000 live births. It can grow rapidly, causing high-output
cardiac failure, polyhydramnios, preterm labor and/or delivery,
or death in utero from nonimmune hydrops. Almost uniformly fatal
in the setting of hydrops, recent successful resections in utero
have been reported.13,14,38 The key to successful
cases has been intervention early in the development of hydrops.
The goal of fetal surgery in sacrococcygeal teratoma is to interrupt the
large vascular connections responsible for nonimmune hydrops. Care
is taken to preserve the anorectal sphincter complex, and a complete
resection of the sacrococcygeal teratoma is not attempted. The resection
of the pelvic component of the fetal sacrococcygeal teratoma must
be performed postnatally. These infants must be followed for at
least 3 years with serial α-fetoprotein levels,
serial MRIs, and physical examinations as surveillance for recurrent
sacrococcygeal teratoma or malignant transformation.39,40
++
Open fetal surgery has also been employed to treat other life-threatening
conditions for which no other therapy exists or conventional approaches
have failed. Examples are resection of pericardial teratomas and
fetal pacemaker placement for fetuses with complete heart block
that develop hydrops despite steroid and β-mimetic
therapy. Perhaps the most significant change in the field of fetal
surgery has been the application of this technique in non–life-threatening
conditions such as myelomeningocele.12 Although
folic acid supplementation has reduced the incidence of myelomeningocele,
it still occurs in up to 1 in 2000 births. While myelomeningocele
is a devastating anomaly, it is not usually fatal in utero. Early
reports suggest that fetal surgery to repair myelomeningocele can
reverse the hindbrain herniation of the associated Chiari II malformation,
slow the rate of enlargement of the ventriculomegaly, and perhaps
decrease the need for postnatal ventriculoperitoneal shunting. The
Management of Myelomeningocele study (MOMS Trial) is a National
Institutes of Health–sponsored prospective randomized clinical
trial to answer the question of whether fetal myelomeningocele repair
reduces the need for postnatal shunting and improves neurodevelopmental
outcome.41 The trial had recruited 130 of the projected
200 patients over 5 years, but the National Institutes of Health
has committed to complete the trial.
++
Bladder outlet obstruction due to posterior urethral valves was
the first structural anomaly treated by open fetal surgery. It was
quickly supplanted by vesicoamniotic shunting because of the markedly
less invasive nature of these shunts. While vesicoamniotic shunts
can restore amniotic fluid and allow lung growth, they do not protect
the kidney or bladder from progressive injury. In fact, over 50% of
successfully treated cases go on to renal failure requiring dialysis
and/or renal transplantation. Often, these children are
poor transplant candidates because of a fibrotic, hypertrophied, poorly
compliant bladder.16,36,37 Recently, open fetal
surgery for vesicostomy creation in bladder outlet obstruction has
again been employed as the most definitive means to decompress the
genitourinary tract and to protect both the bladder and the kidneys.
+++
Ex Utero Intrapartum Treatment
++
Ex utero intrapartum treatment (EXIT) has been one of the most
useful techniques that developed from open fetal surgery for tracheal clip
application. Originally developed as a means of operating with placental
support to remove surgical clips from the trachea of a baby with
congenital diaphragmatic hernia at the time of delivery, it was
applied to management of neck masses such as cervical teratoma and
lymphangioma causing airway obstruction, intrinsic airway obstruction
due to congenital high airway obstruction syndrome, intrathoracic
airway obstruction due to teratoma or congenital pulmonary airway
malformations, as well as a means of safely transitioning to extracorporeal
membrane oxygenation support in severe congenital diaphragmatic
hernia or hypoplastic left heart syndrome.42-45