Looking for the Telltale Gene

A new genetic test allows parents to peer into their unborn children's medical future. Are we ready for this knowledge? A Columbia study looks for answers.

by Claudia Kalb Published Spring 2013
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Trishia Bermudez and her son, Matthew / Photograph Jörg Meyer

Watch video of Columbia researchers discuss prenatal genetic tests here.

Trishia Bermudez was thrilled to find out that she was pregnant last spring. She loved her baby bump and her expectant glow. And she was delighted by the sense of awe and possibility that her growing baby inspired in family and friends. “Everyone is excited for you about the new life you’re bringing into the world,” she says.

During a routine ultrasound at about twenty weeks, Bermudez’s doctor noticed a potential problem. The baby’s kidneys appeared to be enlarged, which is sometimes a sign of a kidney disorder. In the worst case, it could mean death in the womb or within the first year of life.

Bermudez’s doctor sent her immediately to the Center for Prenatal Pediatrics at Columbia University Medical Center (CUMC), one of the nation’s premier institutions for treating high-risk pregnancies.

There, another ultrasound suggested that her baby’s kidneys were fine, having swelled only temporarily. But it revealed a missing nasal bone, an enlarged placenta, and a shortage of amniotic fluid around the fetus. These were likely signs of a chromosomal abnormality in the baby. Bermudez sat down with Ashley Mills, a genetic counselor who specializes in translating complex information about a fetuses’ DNA to parents. Mills offered Bermudez a routine procedure known as amniocentesis, which requires inserting a long needle into the abdomen to collect amniotic fluid. It is unpleasant and somewhat risky — about one in three hundred amniocenteses results in miscarriage — but it would allow doctors to examine her baby’s DNA.

Bermudez agreed, despite her fear of needles. A physician extracted amniotic fluid, created a cell culture, and examined the stained cells under a microscope. The results were encouraging: no genetic mistakes could be seen. This ruled out the possibility that her baby would have Down syndrome, Turner syndrome, or any of the dozens of other conditions that are caused by the sorts of genetic mistakes that are easy to spot on a slide.

But Mills also offered to analyze Bermudez’s baby’s DNA using a computer-based technique that probes even deeper into the genome. Microarray analysis, as it is called, can detect mistakes in genetic code that are one hundred times smaller than those seen under a microscope. These tiny deletions and duplications are the sort that have been linked to autism, developmental delays, schizophrenia, and many other complex conditions. The test therefore provides parents a more detailed picture of their baby’s health than has ever been available before.

“I thought if we went ahead with the test, maybe we’d get some concrete answers about what was going on with my body and my baby,” says Bermudez.

Bermudez agreed to the test. This time, scientists did find something alarming: a missing piece of DNA on chromosome 3. This was a bad sign, but precisely what it meant for the baby was unclear.

“I sat with her for a very long time delivering the news,” says Mills. “I explained that I would have to do lots of research to give her some reliable information.”

Over the next several weeks, Mills studied the area of the genome where Bermudez’s baby had a deletion. There were nine genes in the region that were particularly worrisome, having been implicated in autism, diabetes, cataracts, abnormal blood clotting, epilepsy, leukemia, lymphoma, Parkinson’s disease, and obesity. To narrow down the prognosis, Mills pored over medical literature in hopes of finding references to other people with a DNA deletion that resembled this one. She found none. So she telephoned genetics labs around the country, asking if any other researcher had come across a similar case. Again, no luck.

“This meant that I couldn’t give her percentages or statistics on the likelihood that anything in particular would happen,” says Mills. “All I could say was that, based on the location and size of this deletion, the child would almost certainly have health problems. But what kind of problems? And when? What will he be like when he’s two? When he’s five? It was impossible to say. That’s very difficult news to deliver.”

Mills and Bermudez discussed the baby’s prognosis over a series of visits. They became close, and spent some of their time just chatting and laughing. But the heart of the meetings consisted of Mills preparing Bermudez for the likelihood that her baby would have special needs.

“Every time I went back for a visit, it was something sad,” Bermudez says. “I was coming home and crying and telling my fiancé about it. He felt like we couldn’t enjoy what the pregnancy was really about, which was bringing a new life into the world.”

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