prenatal surgery


Prenatal Surgery

 

Definition

Prenatal surgery is a surgical procedure performed on a fetus prior to birth.

Purpose

In most cases prenatal surgery is performed only when the fetus is not expected to survive delivery or live long after birth without prenatal intervention. The most common prenatal surgeries are for conditions in which the newborn will not be able to breathe on its own.Most prenatal surgeries are performed for:
  • urinary tract obstructions in males, usually caused by a narrowing of the urinary tract, in which urine backs up and injures the kidneys. About 10% of fetal urinary tract obstructions require prenatal surgery to prevent multiple abnormalities and depleted amniotic fluid.
  • congenital diaphragmatic hernia (CDH), a condition in which the diaphragm—the muscle that separates the chest and the abdomen—does form completely. Without surgery about 50% of fetuses with CDH do not survive after birth because of underdeveloped lungs.
  • congenital cystic adenomatoid malformation (CCAM), a condition in which one or more lobes of the lungs become fluid-filled sacs called cysts. Large CCAMs may prevent lung development, cause heart failure, or prevent the fetus from ingesting amniotic fluid.
  • sacrococcygeal teratoma (SCT), tumors at the base of the tailbone. The most common tumor in newborns, occurring in one out of every 35,000-40,000 births, some prenatal SCTs are very large, hard, and full of blood vessels, and can stress the heart.
  • twin-twin transfusion syndrome (TTTS), a condition in which, because of abnormal blood-vessel connections in the placenta, one twin pumps the circulating blood for both twins. Affecting up to 15% of twins sharing a placenta (monochorionic), TTTS can lead to a variety of problems including heart failure.
  • twin:twin reverse arterial perfusion (TRAP) sequence, a condition in which one twin lacks a heart. Occurring in about 1% of monochorionic twins, the healthy twin pumps all of the blood and, if untreated, 50-75% of these normal twins die.
Other conditions that may be treated by prenatal surgery include:
  • various congenital defects that block air passages and will prevent the newborn from breathing on its own
  • various lung malformations
  • omphalocele, a birth defect in which portions of the stomach, liver, and intestines protrude through an opening in the abdominal wall
  • fetal gastroschisis—a birth defect in which the stomach and intestines protrude through improperly formed abdominal wall muscles and float in the amniotic fluid
  • bowel obstructions, usually caused by a narrowing in the small intestine
  • hypoplastic left heart syndrome, in which the blood flow through the left side of the heart is obstructed
  • X-linked severe combined immunodeficiency syndrome
  • spina bifida (myelomeningocele)—the second most common birth defect in the United States, affecting one out of every 2,000 newborns. It is a lesion or hole where the nerves of the spinal cord are not completely enclosed and is not considered to be life-threatening.

Precautions

Prenatal surgery involves:
  • serious risks for the mother and fetus
  • travel to a hospital that performs the procedure
  • possibly having to stay near the hospital until delivery
  • extended postoperative bed rest, sometimes until delivery
  • a significant financial commitment.

Description

Prenatal surgery may be referred to as fetal surgery, antenatal surgery, or maternal-fetal surgery. There are only about 600 candidates for prenatal surgery in the United States each year. Of these, only about 10% actually undergo the procedure. Most prenatal surgeries are performed between 18 and 26 weeks of gestation. Some surgeries may not be covered by insurance.Prenatal surgery usually requires a general anesthetic, although sometimes an epidural anesthetic to numb the abdominal region may be used. The fetus receives the anesthetic via the mother's blood. An anesthesiologist and a perinatologist monitor the heart rates of the mother and fetus during the procedure.Prenatal surgeries include:
  • inserting a device into the fetal bladder to drain urine into the amniotic sac for treating urinary tract obstruction
  • draining or removing CCAMs
  • destroying blood vessels leading to a large SCT
  • amnioreduction for TTTS, in which a syringe through the mother's abdomen is used to remove fluid from the overfilled amniotic sac and replace it in the depleted sac of the twin pumping the blood. The procedure that may be repeated during the course of the pregnancy.
  • destroying abnormal blood vessel connections in the placenta of TTTS twins
  • severing the connections between TRAP sequence twins
  • experimental hematopoietic-stem-cell transplants for X-linked severe combined immunodeficiency syndrome
  • closing the lesion in spina bifida

Open surgeries

In open prenatal surgeries incisions are made through the mother's abdominal wall and the fetus is partially removed from the uterus or the entire uterus is removed through the mother's abdomen. Using ultrasound as a guide, the surgeon feels for the affected fetal part. The surgeon may knead and push on the uterus to move or flip the fetus away from the placenta, the disk-shaped organ within the uterus that supplies the fetal blood. A narrow tube is placed through a tiny hole in the uterine wall to drain and collect the amniotic fluid. Opening the uterus is the riskiest part of prenatal surgery. The first incision is made at a point away from the placenta to prevent damaging it. Following the procedure the fetus is replaced in the uterus and the incision is stitched. Prior to the final stitch the amniotic fluid is re-injected into the uterus. The uterus is repositioned in the mother's body cavity and her abdominal wall is closed.The first successful open fetal surgery was performed in 1981 for a urinary tract obstruction. The first successful open fetal surgery for CDH was performed in 1989.Prenatal open surgery for CCAM requires opening the fetus's chest. If a large cyst does not have a hard component, procedures called thoracoamniotic shunting or catheter decompression may be used to drain it. Otherwise the surgeon must remove part or all of the cyst. The first successful resection (removal) of a CCAM from a fetal lung was performed in 1990. The first resectioning of a fetal SCT was performed in 1992.In prenatal surgery for spina bifida, An incision the size of a small fist is made in the uterus. The surgeon loosens and lifts the tissues of the spinalcanal lesion and stitches them closed. Between 1997 and 2004, more than 200 open surgeries were performed for spina bifida. As of 2005 the surgery was available only as part of a prospective randomized clinical trial.

Less invasive procedures

For urinary tract obstructions a needle may be used to insert a catheter through the mother's abdomen and uterus and into the fetal bladder where it drains the urine into the amniotic fluid. The catheter may have a wire mesh that expands in the bladder to prevent it from plugging up or dislodging.The first successful fetoscopic temporary tracheal occlusion for CDH was performed in 1996. Small openings are made in the uterus and a tiny fiberoptic fetoscope is inserted to guide the operation. A needle-like instrument is used to place a balloon in the fetus's trachea to prevent lung fluid from escaping through the mouth, enabling the lungs to expand, grow, and push the abdominal organs out of the chest. The balloon is removed at birth.Hypoplastic left heart syndrome is treated by passing a needle, guided by ultrasound, through the mother's abdominal wall, into the uterus, and the fetal heart. A catheter is passed through the needle across the fetus's aortic valve. A balloon is inflated, opening the valve and allowing blood to flow through the left side of the heart.RADIOFREQUENCY ABLATION. Radiofrequency ablation (RFA) sometimes is used for SCT. Guided by ultrasound a needle is inserted through the mother's abdomen and uterus and into the tumor. Radiofrequency waves sent through the needle destroy the blood supply to the tumor with heat. This slows the tumor's growth and may enable the fetus to survive until delivery. The first RFA of a SCT was performed in 1998.TRAP sequence also may be treated by RFA. A 3-mm needle targets the exact point where the blood enters the twin without a heart. Using an echocardiographic device, RFA is applied until the blood vessels and surrounding tissue are destroyed and the blood flow is halted. This procedure has eliminated the need for open surgery to treat TRAP sequence.LASER TREATMENT. If TTTS does not respond to amnioreduction, laser treatment to halt the abnormal blood circulation may be attempted. A thin fetoscope is inserted through the mother's abdominal and uterine walls and into the amniotic cavity of the recipient twin to examine the surface placental blood vessels. The abnormal blood vessel connections are located and eliminated with a laser beam. The first successful fetoscopic laser treatment for TTTS was performed in 1999.EXIT. Ex utero intrapartum treatment (EXIT) is a surgery performed for a congenital defect that blocks a fetal airway. The fetus is removed from the womb by cesarean section but the umbilical cord is left intact so that the mother's placenta continues to sustain the fetus. After the air passage is cleared, the umbilical cord is cut and the newborn can breathe on its own. The EXIT procedure is used for various types of airway obstruction including CCAM.

Preparation

The decision to perform prenatal surgery is made on the basis of detailed ultrasound imaging of the fetus—including echocardiograms that use ultrasound to obtain images of the heart—as well as other diagnostic tools. Consultations include a perinatologist, a neonatologist, a pediatric surgeon, a clinical nurse specialist, and a social worker. Since additional congenital defects preclude prenatal surgery, amniocentesis or chorionic villi sampling (CVS) are used to check for chromosomal abnormalities in the fetus.Prior to surgery the mother must:
  • arrange for postoperative bed rest to prevent preterm labor
  • prepare for the possibility of remaining near the hospital until delivery
  • receive betamethasone, a steroid, in two intramuscular injections 12-24 hours apart to accelerate fetal lung maturation
  • wear a fetal/uterine monitor
The mother usually receives medications called tocolytics to prevent contractions and labor during and after surgery:
  • terbutalin
  • indocin suppositories before surgery and up to 48 hours after surgery
  • magnesium sulfate for one to two days after surgery with careful monitoring
  • nifedipine every four to six hours as the indocin is decreased, continuing until 37 weeks of gestation or delivery

Aftercare

In addition to usual post-surgical care, the mother:
  • usually remains in the hospital for four to seven days
  • lies on her side to help prevent contractions and ensure the best possible fetal circulation
  • has a transparent dressing over the abdominal incision for fetal monitoring
  • has continuous electronic fetal/uterine monitoring to check the fetal heart, the uterine response to tocolytics, and to watch for signs of preterm labor.
After discharge from the hospital the mother is on modified bed rest, lying on her side, until 37 weeks of gestation. This increases blood flow to the fetus and reduces pressure on the cervix to help prevent uterine contractions. She sees a perinatologist once a week and has at least one ultrasound per week.

Risks

Most prenatal surgeries are high risk and may be considered experimental. The greatest risk is that the placenta will be nicked during surgery, causing blood hemorrhaging, uterine contractions, and birth of a premature infant who may not survive. Preterm labor is the most common complication of prenatal surgery. Fetoscopic surgeries are less dangerous and traumatic than open fetal surgery and reduce the risk of premature labor. Subsequent children of a mother who has undergone prenatal surgery usually are delivered by cesarean section because of uterine scarring.

Maternal risks

Risks to the mother include:
  • extensive blood loss
  • complications from general anesthesia
  • side effects—potentially fatal—from medications to control premature labor
  • rupture of the uterine incision
  • infection of the wound or uterus
  • psychological stress
  • inability to have additional children
  • death.

Fetal risks

All fetuses that undergo surgery are born prematurely. Those born even six weeks early are at risk for walking and talking delays and learning disabilities. Infants born at 30 weeks of gestation or less are at risk for blindness, cerebral palsy, and brain hemorrhages.About 25% of women undergoing prenatal surgery lose some amniotic fluid, often because of leakage at the uterine incision. Amniotic fluid is essential for lung development and protects the fetus from injury and infection. If all of the amniotic fluid is lost, the fetal lungs may not develop properly. Without the fluid cushion in which the fetus floats, the umbilical cord may be compressed, causing death.Other risks to the fetus include:
  • birth during surgery
  • separation of the tissues surrounding the amniotic fluid sac and the uterus, causing early delivery or interference with blood flow to some fetal body part such as an arm or leg
  • intrauterine infection requiring immediate birth of the fetus
  • further damage to the spinal cord and nerves during surgery to treat spina bifida
  • brain damage
  • physical deformities
  • death.

Normal results

Although fetal surgeries heal without scarring, it is difficult to predict their outcome because relatively few have been performed:
  • Fetal surgery for CDH lessens the severity of the condition so that the fetus usually survives delivery and lives long enough to undergo corrective surgery.
  • Thoracoamniotic shunting for CCAM usually results in infant survival.
  • The infant survival rate following prenatal removal of solid CCAMs is about 50%.
  • RFA to slow the growth of a tumor usually enables the fetus to survive delivery, after which the tumor can be removed.
  • The infant survival rate following prenatal treatment for TTTS is about 70%. Since TTTS is a progressive disorder, early intervention may prevent later complications.

Key terms

Amniocentesis — Withdrawal of amniotic fluid through the mother's abdominal wall, using a needle and syringe, to test for fetal disorders.Amniotic fluid — The watery fluid within the amniotic sac that surrounds the fetus.Cesarean section — C-section; incision through the abdominal and uterine walls to deliver a baby.Chorion — The outermost membrane of the sac enclosing the fetus.Chorionic villus sampling (CVS) — The removal of fetal cells from the chorion for the diagnosis of genetic disorders.Congenital cystic adenomatoid malformation (CCAM) — A condition in which one or more lobes of the fetal lungs develop into fluid-filled sacs called cysts.Congenital diaphragmatic hernia (CDH) — A condition in which the fetal diaphragm—the muscle dividing the chest and abdominal cavity—does not close completely.Echocardiography — Ultrasonic examination of the heart.Ex utero intrapartum treatment (EXIT) — A cesarean section in which the infant is removed from the uterus but the umbilical cord is not cut until after surgery for a congenital defect that blocks an air passage.Fetoscope — A fiber-optic instrument for viewing the fetus inside the uterus.Monochorionic twins — Twins that share a single placenta.Omphalocele — A congenital hernia in which a small portion of the fetal abdominal contents, covered by a membrane sac, protrudes into the base of the umbilical cord.Placenta — The organ within the uterus that provides nourishment to the fetus.Radiofrequency ablation (RFA) — A procedure in which radiofrequency waves are used to destroy blood vessels and tissues.Sacrococcygeal teratoma (SCT) — A tumor occurring at the base of the fetus's tailbone.Spina bifida — Myelomeningocele; a congenital defect in which the fetal backbone and spinal canal do not close completely, allowing the spinal cord and its surrounding membranes to protrude.Tocolytic — A medication that inhibits uterine contractions.Twin:twin reverse arterial perfusion (TRAP) sequence — A condition in which one fetus lacks a heart and the other fetus pumps the blood for both.Twin-twin transfusion syndrome (TTTS) — A condition in monochorionic twins in which there is a connection between the two circulatory systems so that the donor twin pumps the blood to the recipient twin without a return of blood to the donor.Ultrasound — A procedure that uses high-frequency sound waves to image a fetus.Spina bifida arises during the first month of fetal development. Fluid leaking from the spinal cord and exposure of the cord to amniotic fluid causes damage throughout gestation. Lesions higher up in the spinal cord can cause severe deformities, paralysis, and mental retardation. Prenatal surgery may reduce the abnormalities, although it does not cure the condition. Babies who survive prenatal surgery appear to be 33-50% less likely to have hydrocephalus, a condition that requires surgically implanted tubes or shunts to remove fluid from the ventricles (cavities) of the brain. The surgery also appears to reverse hindbrain herniation, in which the back of the brain slips down into the spinal canal, causing breathing and swallowing problems and death in 15% of affected children. Children who had prenatal surgery to treat spina bifida appear to have better brain function than those who did not. However prenatal surgery does not prevent two of the most serious conditions associated with spina bifida: leg movement and bladder and bowel control. As of 2005 the long-term prognosis for these children was not known.

Resources

Books

Bianchi, Diana W., et al. Fetology: Diagnosis and Management of the Fetal Patient. New York: McGraw-Hill, 2000.Casper, Monica J. The Making of an Unborn Patient: A Social Anatomy of Fetal Surgery. New Brunswick, NJ: Rutgers University Press, 1998.

Periodicals

Hedrick, Holly L., et al. "History of Fetal Diagnosis and Therapy: Children's Hospital of Philadelphia Experience." Fetal Diagnosis and Therapy 18, no. 2 (March/April 2003): 65-82.Jones, Maggie. "A Miracle, and Yet." New York Times Magazine July 15, 2001: 38-43.Kalb, Claudia. "Treating the Tiniest Patients." Newsweek June 9, 2003.Paek, Bettina W., et al. "Advances in Fetal Surgery." Female Patient 25, no. 6 (June 2000): 15-18.

Organizations

Fetal Treatment Center, University of California at San Francisco Children's Hospital. 505 Parnassus Ave., San Francisco, CA 94143. 800-RX-FETUS. http://www.ucsfhealth.org/childrens/medical_services/surgical/fetal.Management of Myelomeningocele Study (MOMS). Catherine Shaer, M.D., The George Washington University Biostatistics Center, 6110 Executive Blvd., Suite 750, Rockville, MD 20852. 866-ASK-MOMS. http://www.spinabifidamoms.com.

Other

Bunch, Kathy. Giving Baby a Chance, Before Birth. WebMDHealth. 2001 [cited March 11, 2005]. http://my.webmd.com/content/article/14/3606_466.htm?lastselectedguid={5FE84E90-BC77-4056-A91C-9531713CA348}.Fetal Treatment. UCSF Children's Hospital. April 2002 [cited March 11, 2005]. http://www.ucsfhealth.org/childrens/medical_services/surgical/fetal.Fetal Treatment: Patient Education. UCSF Children's Hospital. March 2003 [cited March 11, 2005]. http://www.ucsfhealth.org/childrens/medical_services/surgical/fetal/moreinfo/patient_education.html.Mayo Clinic Staff. Spina Bifida: Treatment. Mayo Foundation for Medical Education and Research. December 8, 2003 [cited March 11, 2005]. http://www.mayoclinic.com/invoke.cfm?objectid=CB5F085A-6152-42FC-8CFC55380EF705A2&dsection=8.

prenatal surgery

Intrauterine surgical procedures on the fetus. These techniques have been used to repair heart defects and anatomical defects of other organs. See: prenatal diagnosisSee also: surgery