Prenatal surgery





Definition

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

Purpose

Prenatal surgery, also called fetal surgery, antenatal surgery, or maternal-fetal surgery, usually is performed under circumstances in which the fetus is not expected to survive delivery or to live long after birth without prenatal intervention. The most common prenatal surgeries are for conditions in which the child will not be able to breathe on its own after birth. There are only about 600 candidates for prenatal surgery in the United States each year and far fewer prenatal surgeries are performed. Most of these procedures are high-risk and may be considered experimental.

More common prenatal surgeries

Urinary tract obstructions in male fetuses are usually caused by a narrowing of the urinary tract. This can cause the urine, which normally flows out into the amniotic fluid surrounding the fetus, to back up and injure the kidneys. If only one kidney is affected and there is a normal amount of amniotic fluid, prenatal intervention is not required. However, in addition to kidney damage, urinary tract obstructions can lead to multiple abnormalities and depleted amniotic fluid, which endangers the fetus and prevents the lungs from growing. About 10 percent of fetuses with urinary tract obstructions may require prenatal surgery in which a device is placed in the fetus's bladder to drain the urine into the amniotic sac.

Congenital diaphragmatic hernia (CDH) occurs when the diaphragm does not form completely at about eight weeks of gestation, leaving a hole in this muscle that separates the chest and the abdomen. The stomach, intestines, liver, spleen, and kidneys can move into the chest cavity through this hole, which is most often on the left side. Most babies with CDH are treated after birth. However, about 50 percent of fetuses with CDH do not survive after birth because their lungs are too small (pulmonary hypoplasia). A fetus whose liver has moved into its chest, seriously restricting lung development, whose lung-to-head ratio is less than one in four, and whose chance of survival through delivery is less than 50 percent may be a candidate for surgery. CDH fetuses whose livers have not moved into the chest have a survival rate of about 90 percent without prenatal intervention.

Congenital cystic adenomatoid malformation (CCAM) occurs when one or more lobes of the lungs develop into fluid-filled sacs called cysts rather than into normal lung tissue. Most CCAMs disappear on their own or are small enough to not cause problems. Large CCAMs can limit lung development, causing pulmonary hypoplasia. About 10 percent of fetuses with CCAMs are at risk of heart failure because the cysts push into the heart. CCAMs also can push on the trachea and the esophagus where they prevent the fetus from ingesting amniotic fluid. Prenatal surgery to drain or remove the cyst is performed only on severely affected fetuses.

Sometimes prenatal surgery is performed to remove a tumor. Sacrococcygeal teratoma (SCT) is the most common tumor in newborns, occurring in one out of every 35,000 to 40,000 births. It is more common in girls than in boys. These tumors at the base of the tailbone can grow very large. With early diagnosis, most SCT babies are delivered normally and the tumor is removed after birth. However, a small percentage of these tumors are large, hard, and full of blood vessels and may stress the fetal heart. These may be treated with a surgical procedure that destroys the blood vessels leading to the tumor, thereby preventing its growth.

Up to 15 percent of twins who share a placenta (monochorionic twins) have twin-twin transfusion syndrome (TTTS). Because of abnormal blood vessel connections in the placenta, one twin pumps the circulating blood for both twins. As a result the pumping twin has reduced volumes of blood and amniotic fluid and the recipient twin as increased volumes, leading to a variety of problems, including the risk of heart failure in both fetuses. TTTS may be treated by removing fluid from the overfilled recipient amniotic sac and placing it into the depleted sac of the pumping twin. If this fails, prenatal surgery may be used to destroy the abnormal blood vessel connections in the placenta.

Twin-twin reverse arterial perfusion (TRAP) sequence occurs in about 1 percent of monochorionic twins. In a TRAP sequence one twin develops normally and the other lacks a heart. The normal twin pumps all the blood for both twins and is at risk for heart failure. If left untreated 50 to 75 percent of these normal twins die. In prenatal surgery for TRAP sequence, the connections between the twins are severed.

Other prenatal surgeries

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 an opening in the fetus's abdominal wall enables portions of the stomach, liver, and intestines to protrude
  • fetal gastroschisis, a birth defect in which the abdominal wall muscles do not form correctly and the stomach and intestines protrude and float in the amniotic fluid, a condition that occurs primarily in fetuses of mothers in their late teens or early 20s
  • bowel obstructions, usually caused by a narrowing in the small intestine
  • experimental hematopoietic stem cell transplants for X-linked severe combined immunodeficiency syndrome

Hypoplastic left heart syndrome, in which the blood flow through the left side of the heart is obstructed, is the most common congenital heart defect that is a candidate for prenatal surgery. In this condition, which is often fatal, the left side of the heart is very small and stops working.

Spina bifida

Until the late 1990s, prenatal surgery was almost exclusively limited to life-threatening conditions. However in 1994 the first prenatal surgery to treat spina bifida (myelomeningocele) was performed. This is the second most common birth defect in the United States, affecting one out of every 2,000 newborns. It is not considered to be life-threatening.

Spina bifida occurs during the first month of fetal development when a small bit of bone and skin fails to fully enclose the nerves of the spinal cord, leaving a hole or lesion. Depending on the location of the lesion, spina bifida may not require treatment; the higher up the opening in the spinal cord, the more severe the condition, and myelomeningocele can cause severe deformities, paralysis, and mental retardation . The damage appears to be caused by leakage of fluid from the spinal cord and exposure of the cord to amniotic fluid. The risk of infant death is about 10 percent and after the age of one, about 1 percent of affected children die each year.

Surgery for spina bifida requires closing the opening in the cord. Since the damage from spina bifida occurs during fetal development, prenatal surgery may reduce the damage. However, prenatal surgery for spina bifida has become enmeshed in the politics of reproductive rights and fetal rights. As of 2004, prenatal surgery for spina bifida was available only as part of a prospective randomized clinical trial.

Description

The decision to have prenatal surgery is made on the basis of detailed ultrasound imaging of the fetus, including an echocardiogram that uses ultrasound to obtain images of the fetal heart, as well as other diagnostic tools. Consultations include a perinatologist, a neonatologist, a pediatric surgeon, a clinical nurse specialist, and a social worker. Usually only fetuses with a very poor prognosis are candidates for maternal-fetal surgery. Only about 10 percent of those referred for evaluation actually undergo the surgery. Since additional congenital defects preclude prenatal surgery, amniocentesis or chorionic villi sampling (CVS) are used to check for chromosomal abnormalities in the fetus. Prenatal surgeries usually are performed between 18 and 26 weeks of gestation.

Prenatal surgery usually requires a general anesthetic. The fetus receives the anesthetic via the mother's blood. During the operation the anesthesiologist controls the mother's breathing through a tube into her throat and airway. The anesthesiologist and a perinatologist monitor the heart rates of the mother and fetus. For some procedures an epidural anesthetic that numbs the abdominal region may be used instead of general anesthesia.

Open surgeries

Open prenatal surgery requires a procedure similar to a cesarean section (C-section) for delivering a baby through the mother's abdomen. Incisions are made through the mother's abdominal wall. In some procedures the fetus is partially removed from the uterus. In other procedures the entire uterus is removed from the mother's body cavity through her abdomen.

Using ultrasound as a guide, the surgeon feels for the affected fetal part. The fetus must be moved away from the placenta, the disk-shaped organ within the uterus that provides the blood supply to the fetus. The surgeon may knead and push on the uterus to move or flip the fetus. A narrow tube in placed through a tiny hole in the uterine wall, through which the amniotic fluid is drained and collected in syringes. Opening the uterus is the riskiest component of prenatal surgery. The first incision is made at a point away from the placenta to prevent damaging it. A special device simultaneously makes the incision and clamps the edges to prevent bleeding. 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. A tiny hole was made in the bladder of the fetus and a catheter (a long, thin tube) was inserted to drain the urine directly into the amniotic fluid. The first successful open fetal surgery for CDH was performed in 1989.

Prenatal open surgery for CCAM requires opening the fetal chest. If a large cyst does not have a hard component, procedures called thoracoamniotic shunting or catheter decompression may be used to drain the cyst. Otherwise the surgeon must remove all or a portion of the mass. 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.

Between 1997 and 2004, more than 200 open surgeries were performed for myelomeningocele. An incision the size of a small fist is made in the uterus. The surgeon loosens and lifts the tissues of the spinal canal lesion and stitches them closed. The entire procedure takes about one hour.

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 an expandable wire mesh that expands in the bladder to prevent the catheter from plugging up or dislodging.

The first successful fetoscopic temporary tracheal occlusion for CDH was performed in 1996. Small surgical openings are made in the uterus, and a tiny fiber optic fetoscope is inserted to guide the operation. A needle-like instrument enters the uterus through a small incision in the mother's abdomen. A balloon placed in the fetus's trachea prevents lung fluid from escaping through the mouth, enabling the lungs to expand, grow, and push the abdominal organs out of the chest and back into the abdomen. The balloon is removed at birth. In a successful procedure the lungs are developed enough that the baby will breathe on its own 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 can be 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.

A 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 echocardiogram 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 or larger fetoscopes to treat a TRAP sequence.

Laser treatment

TTTS is a progressive disorder and early intervention may prevent later complications. The most common treatment for TTTS is amnioreduction in which a syringe through the mother's abdomen is used to remove amniotic fluid from the overfilled sac and place it in the sac of the other twin. This procedure may need to be repeated during the course of the pregnancy. If TTTS does not respond to amnioreduction, laser treatment may be attempted to stop the abnormal blood circulation. Following detailed ultrasound, 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 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 the fetus's 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.

Precautions

The decision to undergo prenatal surgery is a difficult one. Considerations must include the following:

  • serious risks for the mother and fetus
  • time commitment for the surgery
  • extended postoperative bed rest, perhaps until delivery
  • travel to a hospital that performs the procedure
  • possible need to stay near the hospital until delivery
  • significant commitment of financial resources; some surgeries may not be covered by insurance
  • arrangements for care of other children

Preparation

Prior to surgery the mother will need to do the following:

  • arrange for help and support following the surgery since she will be on bed rest to prevent preterm labor
  • prepare for the possibility of having to remain near the hospital until delivery
  • possibly make arrangements for a blood donor in the unlikely event that she needs a blood transfusion
  • take betamethasone, a steroid, in two intramuscular injections 12–24 hours apart to accelerate lung maturity in the fetus; if delivery occurs earlier than 34 weeks, the mother may have to take it again closer to the delivery date
  • wear a fetal/uterine monitor after hospital admission
  • have urine and blood samples taken
  • have her blood typed and cross-matched in case of the need for a transfusion
  • have an intravenous (IV) infusion of fluid and electrolytes
  • take a sleeping medication
  • sign a surgical consent
  • wear thick elastic stockings
  • take a medication for decreasing stomach acids

The mother usually is given medications called tocolytics to prevent contractions and labor during and after surgery. Tocolytics include:

  • indocin suppositories before surgery and up to 48 hours after surgery
  • magnesium sulfate for one to two days after surgery with careful monitoring
  • nifedipine, a pill given every four to six hours as the indocin is being decreased; usually nifedipine is continued until 37 weeks of gestation or delivery
  • terbutalin in pill form

Aftercare

Following the surgery the mother lies in bed on her side to provide the best circulation to the fetus and to help prevent contractions. The mother will have:

  • an oxygen mask to provide post-anesthetic supplemental oxygen
  • an IV catheter to supply fluids and antibiotics for at least 48 hours after surgery
  • a urinary catheter to collect urine from the bladder for 48–72 hours
  • an epidural catheter to supply constant pain medication, usually morphine, for several days after surgery, followed by oral pain medications
  • a sequential compression device to improve blood circulation in the legs during bed rest
  • a continuous electronic fetal/uterine monitor to check the fetal heart and the uterine response to the tocolytics and to check for signs of preterm labor
  • a transparent dressing over the abdominal incision so that the fetus can be monitored and the incision site observed without removing the dressing

Fluids and food are not taken by mouth until the mother's digestive function returns. She usually remains in the hospital for four to seven days following surgery.

To prevent or treat postoperative lung or circulatory problems, the mother should:

  • practice deep breathing to keep all airways clear
  • perform incentive spirometer exercises, using a small simple device to assist deep breathing and opening of the lungs, five times during each waking hour
  • be turned from side to side at least every two hours to increase circulation and relieve areas of pressure
  • practice foot flexion exercises to improve circulation and help prevent blood clots

After discharge from the hospital the mother will be 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 will be given bed rest exercises and prescribed a special diet. She will see a perinatologist once a week and have at least one ultrasound per week.

Risks

A major risk of prenatal surgery is nicking the placenta, 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 fetal surgery usually are delivered by cesarean section because of scarring of the uterus.

Other risks to the mother include:

  • extensive blood loss
  • complications from general anesthesia
  • side effects, potentially fatal, from medications to control premature labor
  • rupturing of the uterine incision
  • infection of the wound or uterus
  • psychological stress
  • inability to have additional children
  • death

All fetuses that undergo surgery are born prematurely. Infants born even six weeks early are at risk for delays in walking and talking and for learning problems. Infants born at 30 weeks of gestation or less are at risk for blindness, cerebral palsy , and brain hemorrhages.

About 25 percent 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 cushion that enables the fetus to float, the fetus may compress the umbilical cord causing death.

Other risks to the fetus include:

  • birth during surgery
  • membrane separation between 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
  • further damage to the spinal cord and nerves during prenatal surgery for spina bifida
  • intrauterine infection requiring immediate birth of the fetus
  • brain damage
  • physical deformities
  • death

Normal results

Although fetal surgeries heal without scarring, they are rare and risky, and it is difficult to predict the outcome. In general, the following usually occurs:

  • 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 survival.

KEY TERMS

Amniocentesis —A procedure performed at 16-18 weeks of pregnancy in which a needle is inserted through a woman's abdomen into her uterus to draw out a small sample of the amniotic fluid from around the baby for analysis. Either the fluid itself or cells from the fluid can be used for a variety of tests to obtain information about genetic disorders and other medical conditions in the fetus.

Amniotic fluid —The liquid in the amniotic sac that cushions the fetus and regulates temperature in the placental environment. Amniotic fluid also contains fetal cells.

Cesarean section —Delivery of a baby through an incision in the mother's abdomen instead of through the vagina; also called a C-section, Cesarean birth, or Cesarean delivery.

Chorion —The outer membrane of the amniotic sac. Chorionic villi develop from its outer surface early in pregnancy. The villi establish a physical connection with the wall of the uterus and eventually develop into the placenta.

Chorionic villus sampling —A procedure used for prenatal diagnosis at 10-12 weeks gestation. Under ultrasound guidance a needle is inserted either through the mother's vagina or abdominal wall and a sample of the chorionic membrane. These cells are then tested for chromosome abnormalities or other genetic diseases.

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 —A non-invasive technique, using ultrasound waves, used to look at the various structures and functions 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 the air passage.

Fetoscope —A fiber optic instrument for viewing the fetus inside the uterus.

Monochorionic twins —Twins that share a single placenta.

Omphalocele —A birth defect where the bowel and sometimes the liver, protrudes through an opening in the baby's abdomen near the umbilical cord. Placenta —The organ that provides oxygen and nutrition from the mother to the unborn baby during pregnancy. The placenta is attached to the wall of the uterus and leads to the unborn baby via the umbilical cord.

Pulmonary hypoplasia —Incomplete or defective development of the lungs.

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 tailbone in a fetus.

Spina bifida —A birth defect (a congenital malformation) in which part of the vertebrae fail to develop completely so that a portion of the spinal cord, which is normally protected within the vertebral column, is exposed. People with spina bifida can suffer from bladder and bowel incontinence, cognitive (learning) problems, and limited mobility.

Tocolytic drug —A compound given to women to stop the progression of labor.

Twin-twin transfusion syndrome (TTTS) —A condition in identical 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.

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.

Ultrasonography —A medical test in which sound waves are directed against internal structures in the body. As sound waves bounce off the internal structure, they create an image on a video screen. Ultrasonography is often used to diagnose fetal abnormalities, gallstones, heart defects, and tumors. Also called ultrasound imaging.

  • Removal of solid CCAM cysts has a survival rate of about 50 percent.
  • RFA to slow the growth of a tumor usually enables the fetus to survive delivery, after which the tumor can be removed.
  • Survival rates for prenatal treatment of TTTS are about 70 percent.

Prenatal surgery for spina bifida does not cure the condition. However, babies who survive the surgery appear to be 33 to 50 percent 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. This condition can cause difficulties in breathing and swallowing and leads to death in 15 percent of children with spina bifida. In addition, children who have prenatal surgery for spina bifida appear to have better brain function than children who do not have surgery. 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 2004, the long-term prognosis for these children was not known.

When to call the doctor

The doctor should be called if any of the following occurs:

  • The abdominal incision become red, warm, tender to the touch, or is draining fluid.
  • The mother's body temperature rises above 101°F (38.5°C).
  • Fluid is leaking from the vagina.
  • Vaginal bleeding occurs.
  • The baby does not move daily.
  • Persistent back pain, cramping, abdominal tightening, or pelvic pressure occurs.
  • Chest pain or difficulty breathing develops.

Signs of preterm labor include:

  • gas pain
  • abdominal tightening
  • cramping
  • backache
  • pelvic pressure
  • change in vaginal discharge
  • leakage of vaginal fluid
  • bleeding

Resources

BOOKS

Bianchi, Diana W., et al. Fetology: Diagnosis and Management of the Fetal Patient. New York: McGraw-Hill, 2005.

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 (UCSF) Children's Hospital. 505 Parnassus Ave., San Francisco, CA 94143. Web site: <www.ucsfhealth.org/childrens/medical_services/surgical/fetal ;.

Management of Myelomeningocele Study (MOMS). The George Washington University Biostatistics Center, 6110 Executive Blvd., Suite 750, Rockville, MD 20852. Web site: http://www.spinabifidamoms.com.

WEB SITES

Bunch, Kathy. "Giving Baby a Chance, Before Birth." WebMDHealth , 2001. Available online at <http://my.webmd.com/content/article/14/3606_466.htm?lastselected uid={5FE84E90-BC77-4056-A91C-9531713CA348> (accessed January 17, 2005).

"Fetal Treatment." UCSF Children's Hospital , April 2002. Available online at <www.ucsfhealth.org/childrens/medical_services/surgical/fetal ; (accessed January 17, 2005).

"Fetal Treatment: Patient Education." UCSF Children's Hospital , March 2003. Available online at <www.ucsfhealth.org/childrens/medical_services/surgical/fetal/morei fo/patient_education.html> (accessed January 17, 2005).

Mayo Clinic Staff. "Spina Bifida: Treatment." Mayo Foundation for Medical Education and Research , December 8, 2003. Available online at <www.mayoclinic.com/invoke.cfm?objectid=CB5F085A-6152-42FC-8CFC5538 EF705A2&dsection=8> (accessed January 17, 2005).

Margaret Alic, Ph.D.



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