Testing for the Future
Prenatal tests can pinpoint genetic abnormalities

By Heather Morse

When she discovered she was expecting her third child, Pitman’s Amy Winters* was ecstatic. With two easy pregnancies already under her belt, Winters felt confident this pregnancy would be just as simple and worry-free as the others.

But things soon changed when she went to her first doctor’s visit. “It had been five years since I had my youngest daughter, and my obstetrician informed me that since I was going on 35 I was right on the verge of being considered high-risk,” says Winters. “She recommended that once I was a little further along I undergo some genetic tests to rule out any potential problems. Instead of leaving the appointment thinking about decorating the nursery or baby names, my husband and I were stressed and worried.”

In recent years, genetic testing has become a common aspect of prenatal care. Usually, the screening is offered to couples considered at risk for a genetic problem. “Risk factors include advanced maternal age and a family history of genetic disorders,” says Terry Freedman, a nurse practitioner at Cherry Hill OB/GYN. Most medical professionals – who consider women 35 or older to be of “advanced maternal age” – also recommend genetic testing for mothers who have already delivered a child with genetic birth defects, those who have had multiple miscarriages or couples in which one partner has a congenital defect, such as congenital heart disease.

However, notes Freedman, some practices offer genetic testing to all patients – regardless of their risk. Whether a woman is at risk or not, the process “may seem overwhelming and daunting,” says Stephen Sawin, MD, of South Jersey Fertility Center. “Pregnancy alone can be daunting, and there are a number of different tests and abnormalities they screen for, so it can be scary for parents.”

What Tests Can Reveal

The American College of Obstetricians and Gynecologists says that roughly 3 percent of babies born in the United States have a birth defect. There are thousands of different birth defects; many are minor, while some are more serious.

Birth defects that come from an abnormal number of chromosomes, such as Down syndrome, can be identified through certain prenatal tests. “Other abnormalities that can be detected include spina bifida, cystic fibrosis, Tay-Sachs disease and sickle-cell anemia,” explains Sue Spinner, a nurse coordinator at The Children’s Hospital of Philadelphia’s Center for Fetal Diagnosis and Treatment.
While many genetic abnormalities can’t be detected through prenatal testing, Dr. Sawin says, “The field is quickly progressing, and we can do now what we couldn’t do even a year ago.”

Understanding the Tests

Prenatal diagnostic tests can be divided into two types, invasive and non-invasive. Non-invasive tests simply involve a blood test or an ultrasound. Both are routinely performed on all pregnant women.
The most common non-invasive test is the SequentialScreen, which is a blood test conducted in the first and second trimester. The combined screening, which Freedman says poses “no risk to the patient or baby,” is 75 to 87 percent accurate in detecting abnormalities.

Some moms may need additional, invasive testing – amniocentesis or chorionic villus sampling (CVS).

During an amniocentesis, a sample of amniotic fluid (containing fetal cells and therefore the baby’s DNA) is removed from the amniotic sac through a long needle inserted into the uterus via the abdomen. When the needle is inserted, some women feel a prick and a little pressure or cramping while the fluid is being withdrawn. The test can be conducted anytime after 15 weeks of pregnancy, which is precisely when Winters underwent the procedure at the recommendation of her doctor. “It took two weeks for the results to come back, which were the longest two weeks of my life,” she says.
The procedure detects defects with almost 100 percent accuracy. Though the test is extremely accurate, the American Pregnancy Association estimates that the risk of miscarriage following amniocentesis ranges from 1 in 400 to 1 in 200 pregnancies. In Winters’ case, “Everything came back just fine, which was a huge relief.”

During CVS, a doctor, using ultrasound as a guide, inserts a thin tube through the cervix and uses gentle suction to remove a small amount of tissue inside the uterus. Some women feel pain during the procedure. Sometimes the doctor may choose to insert the needle through the abdominal wall.
CVS is more than 99 percent accurate, though 1 in 100 tests produces an unclear result. When this happens, an amniocentesis is ordered. Miscarriage is the primary risk related to CVS, occurring in 1 out of every 100 procedures, according the American Pregnancy Association.

New advances in prenatal testing have also extended to couples undergoing in-vitro fertilization, says Dr. Sawin. The testing identifies genetic defects in fertilized embryos before they are implanted. “The technology has revolutionized things,” he says. “We send the embryos out to a lab and typically have results in as little as 24-48 hours. By and large, the testing is 97 percent accurate. This is a huge advancement for couples who are battling infertility caused by a genetic abnormality.”

Understanding the Unthinkable

While more than 95 percent of prenatal tests come back just fine, those expectant parents who receive news of a likely birth defect in their unborn child suddenly find they have a huge amount of information to process. “We receive calls from parents who are incredibly stressed,” says Spinner. “Their whole idea of reality has just changed, and their world has been turned upside down.”

For these patients, doctors, genetic counselors and medical professionals specializing in fetal abnormalities can be trusted sources of information – and support. “The biggest part of our job is helping these parents with their anxiety,” says Spinner. To prevent additional anxiety, she warns that parents “shouldn’t go Googling everything – that can really be a bad idea.”

Another vital part of coming to terms with a diagnosis, Spinner says, is to “talk to doctors who have experience with the specific birth defect affecting your child and find a medical team that will help you through the remainder of the pregnancy and delivery. The right team can help provide as normal of an experience as possible.”

*Name has been changed