Medical geneticist talks prenatal testing for Down syndrome

by Randy Paulson, Senior Staff Reporter

INDIANOLA, Iowa — Women have more prenatal testing options than ever before to see if their babies will have Down syndrome thanks to advances in the so-called genetic revolution, a medical geneticist said Wednesday night at the annual McBride Lecture in Hubbell Hall.

Dr. Brian Skotko, co-director of the Down Syndrome Program at Massachusetts General Hospital, delivered the annual McBride Lecture to an audience of roughly 170 people consisting of students, faculty and community members.

“Down syndrome is the most common chromosomal condition,” Skotko began, adding that roughly 5,000 people are born with it every year.

“If you are pregnant and you go to an OB’s office right now, and you say, ‘I want a prenatal test’ or ‘I want a test for genetic conditions,’ you don’t just have one option, you have a whole menu of options,” he explained.

On that menu would be what he called appetizers, which are tests that would give the statistical chance of the fetus having Down syndrome. “Not a yes or no response, but a one in something,” Skotko said.

Alternatively, if a woman wants to know for sure whether or not the fetus has Down syndrome, Skotko said she would need something from the main entrée menu, such as a chorionic villus sampling or amniocentesis. Both of these procedures are invasive tests in which a needle is inserted into the pregnant abdomen to obtain samples.

Although the latter tests have a 99.9 percent accuracy rate, Skotko said they also have a 1 percent chance in causing a miscarriage.

In 2011, however, a new item was added to the menu thanks to the genetic revolution.

According to Skotko, this new method involves taking decoding a DNA sample taken from a blood draw to determine whether or not a child will have Down syndrome.

“The hypothesis is: If you are pregnant with a fetus with Down syndrome where there is an overabundance of extra material from chromosome 21, do you have an overabundance of itsy-bitsy fragments of chromosome 21 floating throughout mom’s circulation?”

Extra fragments of chromosome 21 would indicate Down syndrome.

Skotko then shifted gears to explain how the mother’s age impacts the likelihood of a baby having Down syndrome.

“The same test could give a different response and mean something different based on what age you are,” he said, referring to a mathematical chart on his PowerPoint.

A 20-year-old mother, for example, would have a lower chance of having a baby with Down syndrome compared to a mother in her 40s. Therefore, in telling their patients the test results, he said doctors must adjust the results to the mother’s age in order to get a more accurate reading.

In Skotko’s words, “Doctors need to know their math.”

He later explained how more fetuses today are being diagnosed with Down syndrome since more women are waiting until later in life to have children compared to women in the past.

While he explained a fraction of women who received positive diagnoses have chosen to terminate their pregnancies, he said families that carry to term have been found to overwhelmingly love and be proud of their child with Down syndrome.

Toward the end of his lecture, Skotko presented recommendations for how medical professionals can improve the way they communicate prenatal results to patients. According to his research, “81 percent of medical students say they had no training whatsoever on Down syndrome.”

His recommendations included developing standardized guidelines for telling families their child has Down syndrome, providing training to healthcare professionals and ensuring information given to families about Down syndrome is accurate.

Specifically, he said when healthcare professionals present Down syndrome results to families, they should not be presented as positive or negative but as an objective risk assessment.

Results should also be provided by those most knowledgeable about Down syndrome, such as an OB-GYN or a genetic professional. If the results can’t be given in person, a scheduled phone call would be the next best option.

Skotko said as a medical geneticist, he is dedicated to making sure his patients can make an informed decision on how to proceed in their pregnancies upon receiving a diagnosis.

After the lecture, Derek Lyons, professor of chemistry, said Skotko’s presentation opened his eyes to what physicians see and do on a daily basis that he does not. He was also impressed with Skotko’s unbiased approach to his presentation.

“It’s hard to be unbiased, and I think Brian (Skotko) did a great job of showing that, but with data, not with just opinions,” Lyons said. “We all know that’s a challenge. It’s just nice to know that the physicians are thinking of ways to solve the problems and ways to think about moving forward so everyone has better information.”