Prenatal surgery, also called antenatal surgery or fetal surgery, is medical treatment of the fetus before birth, while it is still in the womb. Most fetal therapies are “closed” procedures, performed without opening
the womb. The rarest type of fetal surgery is known as “open surgery,” in which the mother’s abdomen and uterus are cut open to reveal the tiny fetus.
Prenatal surgery has allowed many fetuses with such disorders as lung tumors, urinary tract blockages, and congenital diaphragmatic hernias to be born alive. As of the early 2000s, according to the March of Dimes, over one hundred fetuses have been operated on with an experimental prenatal surgery that repairs spina bifida (a congenital defect of the spinal column). However, prenatal surgery is still in its early stages of development and the success rate is not yet high, even though it is higher for some closed-womb procedures such as the bladder shunt. Risk remains high for both fetus and mother, and prenatal surgery is recommended for only a few
conditions. One technique that has exciting possibilities is fetal stem-cell transplantation in which stem cells, the source of all blood cells, from a dead fetus are injected into a living fetus, providing healthy genetic material in an effort to overcome defective genes in the recipient fetus.
History of fetal surgery
The first successful fetal surgery, a blood transfusion, was performed by A. William Liley in 1963 in Auckland, New Zealand. He used x rays to see the fetus and guide his needle. Liley’s success was unparalleled for years, however. Most doctors considered the pregnant womb as sacrosanct and untouchable. To treat the fetus as a patient, separate from its mother, was unthinkable. That view began to change in the early 1970s with the spread of several new diagnostic tools.
With the introduction of the ultrasound machine, a doctor could bounce sound waves into the pregnant woman’s abdomen and create an image of the fetus on a television-like screen. Amniocentesis and chorionic villi sampling procedures made it possible to remove fetal cells from the pregnant uterus for genetic testing. These tests could determine the presence of Down syndrome and other genetic diseases. With these new tools of prenatal diagnosis, it was possible to identify abnormalities in fetuses as young as two or three months old. Yet this information often left parents with only a few limited choices. They could choose to abort a severely deformed fetus, or they could prepare for the medical treatment of their baby as soon as it was born.
A few medical researchers began imagining another option: could these fetuses be treated before birth? Beginning in the late 1970s, several young physicians began studying obstetrics, genetics, and pediatric surgery in their quest to perform fetal therapy. The International Fetal Medicine and Surgery Society was created in order to support one another’s efforts and share information. This group and another international organization known as the Fetoscopy Study Group provided a forum where new techniques in fetal medicine are presented and debated. Since then, using a variety of procedures, fetal surgeons have successfully drained a blocked bladder, removed abnormal growths from a lung, and repaired a diaphragm, the muscle that divides the abdominal and chest cavities.
More common than open surgery, closed-womb procedures are still rare enough to be practiced at only a few dozen specialized institutions. Sometimes these procedures are called needle treatments. Since the first fetal blood transfusion in 1963, fetal transfusions have become one of the most accepted types of fetal therapy, although they are still uncommon. Transfusions can save the life of a fetus if the blood of the fetus and its mother are incompatible. In the case of Rh incompatibility, for instance, the antibodies in the blood of an Rh negative mother will attack the red blood cells of an Rh positive baby. Guided by ultrasound, the doctor inserts a needle through the mother’s abdomen and injects compatible blood into the umbilical blood vessels. In a similar fashion, doctors use needles to deliver life-saving medications.
Sometimes twins fail to develop normally, and the poor health of one twin jeopardizes the life of the other, healthy twin. Left untreated, such pregnancies typically end with the death of both twins. In this situation, parents might permit the doctor to perform fetal surgery and terminate the abnormal twin in order to save the healthy twin. In a rare condition known as twin-twin transfusion syndrome, the blood circulation of the two twins is connected and one fetus lacks a brain and a heart. In a closed-womb procedure, surgeons have successfully used miniature instruments to tie a knot in the blood vessels linking the two twins. Although this kills the abnormal twin, the other twin is much more likely to survive.
Pregnancies that begin with triplets and quadruplets almost never result in the healthy birth of all the fetuses. Indeed, the mother risks miscarrying the entire pregnancy. In this situation, parents and surgeons may decide to reduce the pregnancy to twins in order to ensure the health of at least some of the fetuses. Unwanted fetuses are killed using a needle to inject potassium chloride into the fetal chest. This stops the heart from beating. Multiple pregnancies are becoming more widespread due to the use of fertility drugs and certain infertility treatments. So-called fetal reduction has therefore become a potentially more common procedure, but it remains highly controversial.
Open surgery is still highly experimental now in the twenty-first century. In 1994, medical researchers had reported only about 55 operations in the previous 14 years. As of 2006, the Center for Fetal Diagnosis and Treatment, at The Children’s Hospital of Philadelphia (Pennsylvania), is one of the few programs available in the world to perform open fetal surgery. Between 1995 and 2006, the Center has received over 7,000 referrals from all U.S. states and 46 countries.
The majority of open surgeries are performed by pediatric surgeon Michael R. Harrison and his team at the Fetal Treatment Center at the University of California, San Francisco (California). Harrison’s team has performed open surgery, at least once, for seven or eight different birth defects. Three types of open surgery have proved most promising: removing lung tumors, treating a blocked urinary tract, and repairing a hole in the diaphragm. Prompt treatment of these conditions early in pregnancy prevents a cascade of other problems in fetal development. A hole in the diaphragm, for instance, allows the stomach and intestines to migrate through the diaphragm and press against the lungs. This condition, known as a diaphragmatic hernia, halts the development of the lungs. Most babies with diaphragmatic hernias are unable to breathe at birth and die.
In open surgery, the pregnant woman is placed under anesthesia. The anesthetic, which crosses the placenta, puts the fetus to sleep as well. The surgeon then cuts through the abdomen and uterus to reach the fetus. This part of the operation is like a cesarean section. Once revealed, the tiny fetus is gently turned, so that the desired body part is exposed to the surgeon’s hands. At 24 weeks, a typical age for surgery, the fetus weighs about 1 lb (0.5 kg) and has arms smaller than a surgeon’s fingers.
When lung cysts are removed, an incision is made in the fetus’ chest, and the abnormal growth is sliced off. Only solid cysts require open surgery. Other types of cysts can be treated without opening the uterus. In a closed-womb procedure, the surgeon uses a hollow needle to install a shunt that drains the cyst into the amniotic sac.
Blockages in the urinary system can also be relieved with either open or closed surgery. When blockages occur, the bladder fills with urine and balloons to immense proportions, sometimes growing larger than the fetus’s head. The grotesque size and pressure of this organ disturbs the normal growth of the kidneys and lungs. In open surgery, the fetus is gently pulled, feet first, out of the uterus until its abdomen is exposed and the blockage can be surgically corrected. In closed-womb procedures, surgeons install a shunt that permits the fetal urine to flow from the bladder into the amniotic sac.
To repair a diaphragmatic hernia, the surgeon makes two incisions into the fetus’ left side: one into the chest and one into the abdomen. Next the surgeon pushes the stomach and intestines back down into their proper place. Then he or she closes the hole in the diaphragm with a patch of waterproof Gore-Tex®, the fabric used in outdoor gear. Rather than close the abdominal incision, the surgeon places a Gore-Tex®patch over the cut in order to allow the abdomen to expand and accommodate its newly returned organs. At birth, this patch is removed. The internal patch remains for life.
After the surgery on the fetus is finished, the mother’s uterus and abdomen are closed. She can usually leave the hospital after eight days of careful monitoring. To prevent premature labor, a common problem after open surgery, the woman must stay in bed and take drugs to quell uterine contractions.
Babies who have successfully undergone surgery are born without scars, a happy and unexpected byproduct of operations performed in the womb. They are usually born early, however. Thus, in addition to their original medical problem, they face the problems of any premature infant. Surgery also has a long-term effect on the mother. Since her uterus has been weakened by the incisions made during surgery, normal labor and delivery is no longer safe. To prevent uterine rupture, she must deliver this baby (and all future babies) by cesarean section, before active labor begins, to prevent uterine rupture.
Success rate of open surgery
When doctors began performing open surgery, in the early 1980s, most of the fetuses died. Some physicians were critical of the attempts. They argued that a healthy woman was put at risk in order to attempt the rescue of a fetus that would most likely die anyway. Others supported the experimental surgery and declared that this was the fetus’ only chance.
Today, open surgery remains a last resort for a small number of birth defects. It is appropriate only if it can result in the normal development of the fetus. Surgery that prolongs the lives of babies suffering from incurable health problems is not acceptable. Neither is surgery that puts the mother at excessive risk. In many cases, medical treatment after the baby is born offers an equal chance of success, provided that the pregnancy is carefully supervised and that delivery is planned at a well-equipped hospital with a neonatal intensive care unit.
Certain aspects of fetal surgery raise thorny ethical issues. Treating a fetus as a patient creates a situation that has never before existed. In the past, experimental treatments for the seriously ill could be justified on the grounds that the patient had everything to gain and nothing to lose. With fetal surgery, that may hold true for the fetus, of course, but the benefits and risks to the mother are far less obvious. Many mothers are willing to do whatever is necessary to give birth to a healthy baby. Yet major abdominal surgery and general anesthesia pose risks to the mother. The regimen she must follow after surgery is uncomfortable. Furthermore, the success rate for some surgeries is quite low. Most types of fetal surgery must be approved by a hospital ethics review board.
Research studies have shown that fetal surgery does not interfere with a woman’s future fertility. Still, ethicists argue that a woman must always have the freedom to choose against fetal surgery. They fear that as the procedures gain acceptance and it proves more successful, women will find it increasingly difficult to say no. They also worry that a judge might order a woman to have fetal surgery against her will. Legal precedent already exists for this kind of dispute between mother and fetus. Pregnant women have been ordered to have unwanted cesarean sections after medical authorities testified that the operation was in the best interest of the unborn baby.
Fetal reduction is the elimination of one or more fetuses of a multiple pregnancy in order to save those remaining, and the practice also raises ethical issues. To a certain extent, the issues duplicate those involved in the abortion debate: when is it ethical to kill a fetus? If a woman plans to abort the whole pregnancy unless a fetal reduction is done, is it wrong to kill some fetuses so that others may live? Though the practice is often recommended in cases where reproductive technologies
Amniocentesis— A method of detecting genetic abnormalities in a fetus; in this procedure, amniotic fluid is sampled through a needle placed in the uterus; fetal cells in the amniotic fluid are then analyzed for genetic defects.
Chorionic villi sampling— A procedure in which hair-like projections from the chorion, a fetal structure present early in pregnancy, are suctioned off with a catheter inserted into the uterus. These fetal cells are studied for the presence of certain genetic defects.
Closed surgery— Medical treatment performed on the fetus without opening the mother’s uterus.
Diaphragmatic hernia— A serious birth defect caused by a hole in the diaphragm, the muscle that divides the abdominal and chest cavities.
Fetal reduction— Surgery performed to abort one or more fetuses in a multiple pregnancy.
Open surgery— Surgery performed directly on the fetus by opening the mother’s abdomen and uterus.
Premature labor— Uterine contractions that occur before the fetus is 37 weeks old, the age it can be born safely.
Twin-twin transfusion syndrome— A condition in which abnormal blood vessels link one healthy fetus and one unhealthy fetus in a multiple pregnancy.
Ultrasound— Another term for ultrasonic waves; sometimes reserved for medical applications.
have proven more successful than intended, some fetal surgeons will not perform fetal reductions.
Fetal surgery is no longer limited to a few techniques. With advances in knowledge and improvements in equipment, new opportunities for the treatment of more birth defects will emerge. The unexpected discovery that fetuses heal without scarring suggests that cleft palate and other facial defects might be conducive to repair in the womb. Further research is needed, however, before surgery can be justified for conditions that are not life-threatening.
Advances in fetal surgery are expected to benefit other fields of medicine as well. New strategies to prevent early labor in fetal-surgery patients, for instance, can be applied to any pregnant woman who is at risk for early labor. In a similar fashion, new tools developed for fetal surgery may find other uses in medicine. Further understanding of scarless healing may also lead to innovations in the treatment of adult surgical patients.
See also Embryo and embryonic development.
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