Genetic diagnosis goes in utero

Children today seem to do things at younger ages: they read, ride bikes, and learn to use computers sooner than did their forebears. They’re also being diagnosed with genetic disorders earlier than ever – in utero, in fact.

“Genetics has traditionally been a pediatrics subspecialty, because it was devoted to identifying genetic syndromes in children and making sure those children got special care,” says Katharine Wenstrom, M.D., professor of Obstetrics and Gynecology. “Now that we know the etiology of many genetic diseases, diagnosis for a wide variety of problems – not just the traditional things – has moved into the prenatal period.”

Wenstrom directs the Reproductive Genetics Program in the Division of Maternal-Fetal Medicine. A major goal of the program is to identify fetuses with genetic problems in order to offer prenatal treatments, when available, and improved pregnancy care.

“There are many birth defects that can benefit from prenatal treatment,” she says, “and in some cases simply planning the location of the delivery and having certain specialists available can really improve outcome for babies with birth defects and other problems.

“I think in the community prenatal diagnosis is perceived as a search and destroy mission – that we’re looking for abnormal pregnancies and the only option is termination. That’s not true.”

Bladder outlet obstruction, for example, is a rare but usually lethal birth defect. The fetal urine that exits from the bladder is the amniotic fluid that the baby must “breathe” in and out during lung development. Without it, lung development fails. Now, when prenatal ultrasound reveals bladder outlet obstruction, additional tests are performed to determine whether the kidneys are functional. If they are, Wenstrom and colleagues can insert a fetal bladder shunt to divert the urine out of the bladder and into the amniotic cavity, restoring the amniotic fluid volume and thus supporting lung development, as well as protecting the still developing kidneys. A variety of prenatal therapies are available for other kinds of fetal abnormalities.

The Reproductive Genetics Program also offers screening programs for low-risk patients as well as prenatal diagnosis services to patients who are suspected of having a problem.

Wenstrom brings a unique perspective to the program. She is one of fewer than 50 physicians in the country who are board certified in both Maternal-Fetal Medicine (high risk pregnancy) and in Clinical Genetics. The program also draws on the skills of Martha Dudek, M.S., CGC, a genetic counselor with expertise in prenatal diagnosis. Together, the team interprets screening tests for patients and offers counsel on next steps.

Fetal screening tests of various sorts have been around for decades, Wenstrom notes, but there are now many more general screening tests for low-risk patients and also many specific tests for certain genetic syndromes. Ultrasound technology also has improved dramatically, she points out.

“We’re identifying fetal defects prenatally much more often than we used to, and we’re able to put all the problems together and make a specific fetal diagnosis much more accurately than we were able to do in the past,” she says.

For women whose fetuses have abnormalities, the Center for Advanced Maternal-Fetal Care offers “one stop” care for both the pregnant mother and her baby.

John Pietsch, M.D., professor of Pediatric Surgery, Bill Walsh, M.D., professor of Pediatrics, and Wenstrom are the co-directors of the center at the Monroe Carell Jr. Children’s Hospital at Vanderbilt. The multidisciplinary group includes specialists in Maternal-Fetal Medicine, Neonatology, Pediatric Cardiology and a variety of pediatric surgical specialties including Neurosurgery, General Surgery, Urology and Plastic Surgery. The Center also includes geneticists, social workers and ethicists.

“The patient is evaluated by all the specialists who will impact on her child’s care and development, all in a single visit,” Wenstrom says. “Then we sit down as a group and discuss optimal management, so the patient gets the benefit of all of us talking to each other to come up with the best plan.

“That is really unusual in my experience.”

Wenstrom adds that having an ethicist in the group is particularly important.

“Some of our cases are so unusual that there’s no precedent to guide management, and it’s not clear what the most ethical and humane course of action is. We decide as a group what we can offer, and what we should offer.” VM
- LEIGH MACMILLAN