Fetal surgery

Fetal surgery is any of a broad range of surgical techniques that are used to treat birth defects in fetuses who are still in the pregnant uterus.

• Open fetal surgery involves completely opening the uterus to operate on the fetus.
• Minimally invasive fetoscopic surgery (fetendo) uses small incisions and is guided by fetoscopy and sonography.

Types

Open fetal surgery

Technique

Tocolytics are generally given to prevent labor.^[1] However, these should not be given if the risk is higher for the fetus inside the womb than if delivered, such as may be the case in intrauterine infection, unexplained vaginal bleeding and fetal distress.^[1]

Regarding anesthesia, an H₂ antagonist is usually given the evening before and the morning of the operation, and an antacid is usually given before induction to reduce the risk of acid aspiration.^[1] Rapid sequence induction is usually used for sedation and intubation.^[1]

Open fetal surgery is similar in many respects to a normal cesarean section performed under general anesthesia, except that the fetus remains dependent on the placenta and is returned to the uterus. A hysterotomy is performed on the pregnant woman. Once the uterus is open and the fetus is exposed, the fetal surgery begins. Typically, this surgery consists of an interim procedure intended to allow the fetus to remain in utero until it has matured enough to survive delivery and neonatal surgical procedures.

Upon completion of the fetal surgery, the fetus is put back inside the uterus and the uterus and abdominal wall are closed up. Before the last stitch is made in the uterine wall, the amniotic fluid is replaced.

The mother remains in the hospital for 3–7 days for monitoring and is required to subsequently deliver the baby via a second cesarean section. Often babies who have been operated on in this manner are born pre-term.

Safety and complications

The main priority is maternal safety, and, secondary, avoiding preterm labor and achieving the aims of the surgery.^[1] Open fetal surgery is possible first after approximately 18 weeks of gestation due to fetal size and fragility before that, and up to approximately 30 weeks of gestation due to increased risk of premature labor and, practically, the preferability of delivering the child and performing the surgery ex utero instead.^[1] The risk of premature labor is increased by comcomitant risk factors such as multiple gestation, a history of maternal smoking, and very young or old maternal age.^[1]

Open fetal surgery has proven to be reasonably safe for the mother.^[1] For the fetus, safety and effectiveness are variable, and depend on the specific procedure, the reasons for the procedure, and the gestational age and condition of the fetus. The overall perinatal mortality after open surgery has been estimated to be approximately 6%, according to a study in the United States 2003.^[2]

All future pregnancies for the mother require cesarean delivery because of the hysterotomy.^[1] However, there is no presented data suggesting decreased fertility for the mother.^[1]

Indications

Prenatal repair of neural tube defects such as myelomeningocele and spina bifida is a growing option in the United States. Although the procedure is technically challenging, children treated with open fetal repair have significantly improved outcomes compared to children whose defects are repaired shortly after birth.^[3] Specifically, fetal repair reduces the rate of ventriculoperitoneal shunt dependence and Chiari malformation, while improving motor skills at 30 months of age compared to post-natal repair. Children having fetal repair are twice as likely to walk independently at 30 months of age than children undergoing post-natal repair. As a result, open fetal repair of spina bifida is now considered standard of care at fetal specialty centers.

Other conditions that potentially are treated by open fetal surgery include:

• Congenital diaphragmatic hernia (if indicated at all, it is now more likely to be treated by endoscopic fetal surgery)
• Congenital cystic adenomatoid malformation
• Congenital heart disease
• Pulmonary sequestration
• Sacrococcygeal teratoma

Minimally invasive fetal surgery

Schematic illustration of endoscopic fetal surgery for twin-to-twin transfusion syndrome

Minimally-invasive fetoscopic surgery (aka Fetendo) uses real-time video imagery from fetoscopy and ultrasonography to guide very small surgical instruments into the uterus in order to surgically help the fetus. The name Fetendo was adopted for the procedure because of how the video-based manipulation recalls a child's video game.

Less invasive than open fetal surgery, some fetal surgeries can be achieved with just a small guided wire sent through a needle-puncture of the skin (percutaneous), though in some cases it may require that a small opening be made in the mother's abdomen. The fact that it is less invasive reduces the mother's postoperative recovery and lessens the troubles with preterm labor.

Minimally-invasive fetoscopic surgery (or Fetendo) has proven to be very useful for some, but not all, fetal conditions. Some examples include:

• Twin-twin transfusion syndrome – Laser Ablation of Vessels
• Fetal bladder obstructions
• Aortic or Pulmonary Valvuloplasty – opening the Aortic or Pulmonary fetal heart valves to allow blood flow
• Atrial Septostomy – opening the inter-atrial septum of the fetal heart to allow unrestricted blood flow between the atriums
• Congenital diaphragmatic hernia – Balloon tracheal occlusion
• Spina bifida – Fetoscopic closure of the malformation

History

Fetal surgical techniques using animal models were first developed at the University of California, San Francisco in 1980 by Dr. Michael R. Harrison and his research colleagues.

On April 26, 1981, the first human open fetal surgery in the world was performed at University of California, San Francisco under the direction of Dr. Michael Harrison.^[4] The fetus in question had a congenital hydronephrosis, a blockage in the urinary tract that caused the bladder to dangerously extend. To correct this a vesicostomy was performed placing a catheter in the fetus allowing the urine to be released normally. The blockage itself was removed surgically after birth.^[5]

Further advances have been made in the years since this first operation. New techniques have allowed additional defects to be treated and for less invasive forms of fetal surgical intervention.

See also

• fetoscopy
• EXIT procedure
• Pediatric surgery
• MOMS Trial
• Spina Bifida
• NAFTNet
• Samuel Armas

References

Further reading

• Sutton LN (February 2008). "Fetal surgery for neural tube defects". Best Pract Res Clin Obstet Gynaecol 22 (1): 175–88. doi:10.1016/j.bpobgyn.2007.07.004. PMC 2293328. PMID 17714997.