More than half of the 3.9 million pregnant women in the United States will nevertheless take this blood test, and 125,000 will undergo an amnio. But the popularity of the tests belies their shortcomings. First and foremost: neither the blood-screening test nor amniocentesis can be done before the second trimester. Amnios performed earlier than 15 weeks into pregnancy put women at higher risk of miscarrying, leaking amniotic fluid and delivering a baby with a severe clubfoot. Even chorionic villus sampling, in which a highly trained doctor extracts tiny parts of the placenta for chromosomal testing, cannot be done earlier than 10 weeks into pregnancy–and results take at least seven days to come back. “If you’re going to end pregnancies, earlier is better,” says Arthur Caplan, director of the Center of Biomedical Ethics at the University of Pennsylvania. That’s why the push is on for more accurate, earlier prenatal tests. They are just one of the high-tech tools that are giving women a better chance than ever of having a safe pregnancy and a healthy newborn.
Parents in the new millennium will trade their current blurry ultrasound pictures for clearer, three-dimensional photos of their fetuses. But the goal isn’t to start the baby album with a better picture. Rather, the new 3-D machines should provide more precise images of the fetal brain and heart, and detect hard-to-spot abnormalities such as cleft lip and palate (one in 930 births) and clubfeet (one in 735).
Ultrasound can also be combined with a blood test for an even clearer crystal ball. Scientists are studying whether the combination can tell if a 10- to 14-week fetus is likely to have either Down syndrome or a form of severe mental retardation called trisomy 18. The ultrasound looks for loose skin in the neck of the fetus, which indicates the presence of three chromosome 21s, and hence Down syndrome. It detects more cases, and can be done earlier, than existing tests for these conditions. “The vast majority of women are going to leave [after the test] feeling good about their pregnancy,” says Eugene Pergament, director of reproductive genetics at Northwestern University.
Another test that will be done early in pregnancy analyzes maternal blood. Fetal cells, it turns out, leak into the mother’s circulatory system. Although the cells are few and far between, “for the past several years [we have] been trying to find these needles in the haystack,” says Mark I. Evans, acting chairman of OB-GYN at Wayne State University in Detroit. Now researchers are getting better at it. Within a decade, fetal DNA analysis “could replace everything” from blood-screening tests to amnios, says Dr. Ronald Wapner, director of maternal fetal medicine at Jefferson Medical College in Philadelphia. Parents would learn about chromosomal abnormalities weeks earlier than now.
And that’s not all they would learn. Fetal DNA holds the child’s genetic blueprint, and with a new invention physicians will be able to read it. The device is called a DNA chip, or “biochip.” It consists of thousands of strands of DNA. When a sample of blood is dropped onto the chip, DNA in the blood matches up with DNA on the chip. A laser reads the chip, and thus can tell whether the fetus carries virtually any gene that scientists have identified. That means physicians will be able to tell if a fetus is at risk for disorders such as Down syndrome, as well as hundreds of genetic diseases that strike only in adulthood, such as Alzheimer’s and cancer. Eventually embryos conceived through in vitro fertilization could be tested before being implanted in the mother-to-be. Couples could opt not to implant ones at high risk for, say, juvenile diabetes or breast cancer. Yet this “advance” raises troublesome ethical issues. “I could see society saying, ‘We don’t want to pay [to treat] any babies with genetic diseases. You could have prevented them’,” says Caplan.
Even more important than detecting problems is treating them. Highly trained surgeons now operate on fetuses about a dozen times a year, repairing hernias, lung malformations, urinary-tract obstructions and spina bifida, a condition that leaves an opening near the spinal cord and causes paralysis. Working with cameralike “endoscopes” and instruments that pass through the uterine wall without making an incision, doctors hope to correct cleft lip and palate, too. Some surgeons even foresee performing open-heart surgery on fetuses. Still, fetal surgery remains controversial largely because it can cause preterm birth. “It really hasn’t revolutionized obstetrics in terms of changing overall outcome for any great number of people,” cautions OB-GYN Fredric Frigoletto, chief of obstetrics at Massachusetts General Hospital. But advocates say it’s far cheaper to correct birth defects before delivery than to provide a lifetime of care.
When all the tests point to a healthy fetus, just about the only worry left is preterm labor, the No. 1 problem in obstetrics. Some 10 percent of U.S. babies are born less than 37 weeks into pregnancy, which increases the risk of everything from blindness and deafness to cerebral palsy. “The damage that preterm birth causes can last for life,” says James McGregor, professor of OB-GYN at the University of Colorado at Denver. “If you can get close to 37 weeks, you’re kind of in the clear. You don’t get brain damage. You don’t get lung damage. You don’t have increased risk of cerebral palsy.” To avoid all that, a $90 test measures the amount of a form of estrogen called estriol in a pregnant woman’s saliva. Estriol levels usually start climbing three weeks before labor. Women at risk for early delivery (because of cramping, illness, a fetal abnormality or a previous early delivery) can now simply provide about a tablespoon of saliva and learn their estriol level within two days. If the level indicates they are about to go into labor, and if it’s not time for that, the obstetrician can try to figure out why and treat the cause. To help detect other conditions that can trigger early delivery, some doctors are also performing a $100 test for high levels of a molecule called fibronectin. (They collect it from the cervix with a Q-Tip.) A high level of fibronectin means the uterus is separating from the (probably inflamed) amniotic sac. Moms are vigorously treated for the infection, which can otherwise precipitate early labor.
And who would have guessed that the space program would help prevent preterm deliveries? Scientists at NASA have created a 1i-inch pill-shaped transmitter– implanted into the uterus about 27 weeks into pregnancy–that measures contractions. They’re also working on transmitters to measure fetal acidity, temperature and heart rate, all of which reflect the fetus’s health. If the transmitter costs $1,000 and saves $300,000 in medical costs from problems caused by a preterm birth, it’s well worth it, argues John Hines of NASA’s Ames Research Center.
Expect changes even in electronic fetal monitoring, used to detect babies’ heart rate during labor. Now the monitors are used on 98 percent of pregnant women. The heart rate supposedly shows whether the baby is getting enough oxygen. If he is not, most obstetricians order an emergency Caesarean section. But a device under development would directly measure how much oxygen the fetus is receiving, rather than making an educated guess based on the heart rate, which can raise false alarms. If the fetus is getting plenty of oxygen after all, despite a high heart rate, the mom could continue natural labor instead of undergoing a C-section. For that’s the goal of all these tests anyway: making sure that the fetus is developing normally and setting the mother-to-be’s mind at ease.
