Development of Prenatal Diagnostic and Surgical Techniques
Development of Prenatal Diagnostic and Surgical Techniques
Since 1950, the development of prenatal diagnostic and surgical techniques has transformed the field of obstetrics. Parents are now able to access detailed information about their children before birth. Birth defects are now not only discernable, but sometimes correctable before birth, resulting in a lower infant mortality rate and a healthier population of children. There is some concern, however, that this technology could be misused.
Since the early 1970s, prenatal screening has become a routine part of a pregnant woman's medical care. Certain tests, including ultrasound and amniocentesis, not only diagnose a disorder in the unborn baby, but also give the mother the opportunity to have an abortion if she learns, for example, that her baby has Down syndrome and will thus be mentally impaired. Medical researchers, however, were not content merely to detect birth defects in the fetus; they then looked for ways to help the unborn baby. This search led to the first successful prenatal surgery at the University of California at San Francisco. Today, there are several centers in the United States and other countries that specialize in fetal surgery to correct birth defects that were discovered in prenatal testing.
Prenatal screening and testing are done at different stages in a woman's pregnancy. During the first trimester, the pregnant woman has a blood test to measure certain substances in her blood. Specific amounts of these substances could indicate if the fetus has Down syndrome. Between the 14th and 22nd week, during the second trimester, another blood test can tell if the fetus has neural tube defects.
Even if the results from the blood tests are positive, the fetus may not necessarily have a problem. Additional testing is done to ascertain whether or not the unborn baby has Down syndrome, spina bifida (a neural tube defect), or another problems. Although tests such as ultrasound and amniocentesis cannot diagnose every problem, they are nevertheless an important part of prenatal care.
The original concept of ultrasound dates back to the time when the Titanic sunk, and a British scientist developed a method to search for icebergs. His technique was then used during World War I to detect submarines. Also called sonar (for sound navigation and ranging), ultrasound is still used as a navigational tool by ships all around the world. Adapted for medical use after World War II, ultrasound became an important part of prenatal care by 1970. Ultrasound uses high frequency sound waves that are above the range of human hearing; tissues absorb some of the waves, and other waves are reflected back to form an image on a special type of television screen.
Because doctors learn so much from the reflected image of the fetus, ultrasound is now the most common prenatal test. More than 80 percent of pregnant women in the United States receive an ultrasound test between the 10th to 13th week of pregnancy. Doctors use ultrasound not only to diagnose a pregnancy, but also to determine the fetus's age and sex, observe a multiple pregnancy, or to detect certain abnormalities, such as an ectopic pregnancy. (Also called tubal pregnancies, ectopic pregnancies are serious conditions that can result in severe cramping and internal bleeding; they occur when the fertilized egg develops outside the uterus, often in a fallopian tube.) Ultrasound is also an invaluable tool during fetal surgery to guide the physician as he or she operates on the tiny fetus.
Another important prenatal test is amniocentesis, available to women whose baby may be at a high risk of a chromosomal abnormality. The early pioneer of amniocentesis was Douglas Bevis, whose work was done in the early 1950s. Unlike ultrasound, amniocentesis can determine if the fetus has either spina bifida or Down syndrome. To perform amniocentesis, the doctor uses ultrasound to guide a needle into the abdomen of the pregnant woman between the 16th and 18th week of her pregnancy. A sample of the fluid that surrounds the fetus (the amniotic fluid) is taken. Tests are then performed on the cells within the fluid to determine if the fetus has a chromosomal disorder.
Two other prenatal tests are cordocentesis and CVS. Cordocentesis is performed after 20 weeks of pregnancy; blood is taken from the fetus by way of the umbilical cord. CVS, or chorionic villus sampling, was developed by Dr. Evans at Wayne State University and is performed between the 10th and 12th weeks; this procedure uses a catheter to remove only a small sample of the chorionic villi from the placenta. Both cordocentesis and CVS help determine if the unborn baby has a genetic disorder.
Prenatal testing is not risk-free, however. Amniocentesis, cordocentesis, and CVS carry a miscarriage rate between 1 and 3 percent. Additionally, CVS can even cause certain birth defects. Therefore, the mother must be informed of the inherent risks and sign a consent form allowing the doctor to proceed with these prenatal tests.
With the advances in prenatal testing, doctors and their patients could literally see if the unborn fetus had any problems. But until about 1990, the mother and her doctor had few options if a test, for example, revealed that the unborn baby had a debilitating condition, such as spina bifida, or a life-threatening defect as a certain type of hernia or urinary obstruction. Today, the field of fetal surgery has advanced, and treatment centers around the world offer new hope to parents and their unborn child.
Prenatal or fetal surgery had its beginnings in the 1960s in New Zealand. There, Dr. A. William Liley (1929-1983) developed a technique for prenatal blood transfusions for a fetus with a blood disease. In 1963 Liley performed his first successful transfusion on a 32-week-old fetus. The parents were so grateful that they named their son after Liley. Although this type of transfusion is no longer necessary, Liley is still considered the "Father of Fetal Surgery."
There was little progress in the field of fetal surgery for the next 20 years. By 1980, at the University of California at San Francisco and at Wayne State University in Michigan, medical researchers were working first on the fetuses of lambs and monkeys. The doctors at both universities shared their ideas and data, and were soon ready to apply their findings to human fetuses. The first open fetal surgery was performed at UCSF in April 1981, when doctors placed a catheter in a fetus with a urinary obstruction. In 1987 Dr. Mark Evans of WSU was also successful in treating a 14-week-old fetus for obstructive uropathy. In June 1989 the UCSF team performed the first successful open fetal surgery for a diaphragmatic hernia.
There are two basic approaches to fetal surgery: open or in utero. In open fetal surgery, the doctor opens the mother's uterus and operates directly on the fetus, replacing it back in the uterus when the operation is completed; the pregnancy then continues normally. In utero surgery means that the doctor operates through the uterine wall with fiber-optic instruments. Physicians choose the open approach for some conditions; however, most now prefer in utero or endoscopic surgery. The term "fetoscopy" is used now to describe fetal surgery that uses fiber-optic instruments and is thought to be a safer and easier approach than open fetal surgery. Dr. Ruben Quintero, Director of Fetal Endoscopy at Wayne State University, has vigorously pursued the use of endoscopes—light scopes and viewers—not only to diagnose, but also to treat birth defects.
At Vanderbilt University Medical Center in Tennessee, open fetal surgery is the method of choice for treating fetuses with spina bifida. An opening in the spinal cord, spina bifida leads to severe mental and physical disabilities; some babies also develop hydrocephalus or water on the brain. At Vanderbilt, doctors have successfully treated several unborn babies diagnosed with spina bifida. In 1997 Dr. Noel Tulipan and Dr. Joseph Bruner perfected the open fetal surgical approach to close the lesion on a fetus's spinal cord. They now believe that the open surgery method offers a better outcome than endoscopic surgery for the baby with spina bifida. Tulipan and Bruner performed the first fetal surgery for hydrocephalus in 1999. They placed a shunt in utero, and a healthy baby was later born.
Fetal surgery does, however, have some drawbacks. There are risks for both mother and baby. For the mother, fetal surgery could lead to infections, diabetes, or blood loss. The most common fear is the possibility of the mother's going into early labor and delivery. A premature infant is then at risk for blood transfusions, brain and lung damage, and even death.
Fetal surgery is also expensive, costing tens of thousands of dollars and requiring a cesarean operation later to deliver the baby. Also, there are fewer than 20 centers in only five or six countries that perform fetal surgery.
Doctors and researchers have made wondrous strides in recent decades in the field of fetal medicine, but their progress has also raised troubling moral and ethical questions. After an ultrasound in China and India, where male children are so highly valued, parents often choose to abort a female fetus. In the United States, there are physicians who support abortion and those who are pro-life. Will these doctors offer the same prenatal testing to their patients, even if such a test means a parent may opt for an abortion of a defective fetus? One wonders if the future of mankind will be a "master race" of physically perfect human beings. Will genetic testing mean that we will no longer tolerate a newborn who has a disease or deformity? Will the expense of fetal surgery mean that only the wealthy will have perfect babies? Doctors and parents alike must struggle with these issues as the world enters the twenty-first century.
M. E. ELGHOBASHI
Casper, Monica J. The Making of the Unborn Patient: A Social Anatomy of Fetal Surgery. New Brunswick, NJ: Rutgers University Press, 1998.
Harrison, Michael R. Atlas of Fetal Surgery. New York: Chapman & Hall, 1996.
Manning, Frank A. Fetal Medicine: Principles and Practice. Norwalk, CT: Appleton & Lange, 1995.
Nightingale, Elena O. Before Birth: Prenatal Testing for Genetic Disease. Cambridge: Harvard University Press, 1990.
Oakley, Ann. The Captured Womb: A History of the Medical Care of Pregnant Women. New York: Blackwell, 1984.