Prenatal Genetic Tests Can Lead to Tough Choices
Thursday, February 22, 2007
All pregnant women in California who get regular prenatal care are offered a genetic screening test. This test indicates whether their baby is at risk of having Down syndrome or other genetic birth defects. What women do with the test results is a matter of personal choice. KPBS health reporter Kenny Goldberg has the story.
Last year, Kim Capello was pregnant with her third child. As part of her routine pre-natal care, she had a blood test that screens for certain genetic disorders.
Capello: And a week later, my midwife called me to say that I had a high risk of having a baby with Down syndrome.
Capello had another screening test. But it was inconclusive. So to find out for sure, she had an amniocentesis. That procedure involves inserting a needle into the abdomen, and extracting some amniotic fluid.
Capello was nervous about it, because an amnio carries a small risk of miscarriage. Nonetheless, Capello and her husband needed to know what was up with their baby.
They soon found out. The test said the baby definitely had Down syndrome.
Capello: Basically, I just was frozen, I mean I just was in shock and very sad, and we cried a lot, because we were so, just fearful of what to expect, and you know, it wasn't something you plan or really think about.
Kim Capello and her husband had an agonizing decision to make. Should they terminate the pregnancy? Or, should they have the baby anyway, knowing it would likely be mentally retarded?
About 120,000 babies are born in the U.S. each year with some sort of birth defect. All pregnant women in California who get prenatal care are offered what's called an AFP test. This blood test is usually given early in a woman's second trimester. It identifies whether a fetus has an increased risk of having Down syndrome, or a neural tube defect like spina bifida.
Dr. Andrew Hull is a specialist in perinatal medicine.
Hull: Many of the patients I see have an abnormal screening test, and they come seeking either evaluation and reassurance that the screening test is wrong, or looking for a definitive test to see if the screening test is correct.
Hull points out the AFP test has about a 5 percent false positive rate. So as a follow up upon request, he performs what's called a Level 2 ultrasound. Hull says this exam helps doctors look for other indicators.
Hull: And there are things that we see on ultrasound that aren't really structural abnormalities like a heart defect or a limb defect, but they're more soft signs of chromosomal abnormality and there are a lot of those we look for. And then, based on the ultrasound we can tell the patient whether the screening test is more or less likely to be correct.
But Hull says the definitive test is an amniocentesis.
Dr. Marilyn Jones is director of genetics at Rady Children's Hospital. She says pre-natal genetic screening isn't foolproof.
Jones: Chromosome problems account for only about ten to 15 percent of all birth defects. So you're not screening for everything when you look for chromosomes and you look for abdominal wall defects and neural tube defects. You're screening for some common ones, but certainly that leaves a huge number that we don't even test for.
And when the tests do indicate a genetic problem, there's really nothing doctors can do about it.
Jason Chibuk is a genetic counselor at UCSD. Couples often come to see him when they've had a troubling test result.
He says he tries to help people sort through all of the information. Chibuk tells couples about the baby's possible condition, and what could lie ahead. But Chibuk says he leaves the decisions up to them.
Chibuk: I can give you the math, and I can tell you what a test has said, or what the risks are, what the likelihoods are, what are the chances that we would cause a problem by looking for these answers. But they need to make a decision on how this would impact their life, and whether they think that they would be able to deal with the challenges that come with a given diagnosis.
Kim Capello and her husband knew their baby would have Down syndrome. They decided to have him anyway.
Jake was born in December. Capello says it's too soon to tell how Down syndrome will affect Jake. But so far, so good.
Capello: He's doing great, I mean, we're very happy and feel very blessed and lucky to have him.
California is on the verge of changing its prenatal genetic screening program. This summer, the state will introduce what's called a quadruple screen that has a better detection rate for Down syndrome.Kenny Goldberg, KPBS News.