April 17, 2018
Did you know ... that DNA sequencing now allows us to test for specific genomic variants in an unborn baby using a small sample of a pregnant mother's blood?
Pregnancy can be a stressful time, and for many years prenatal genetic testing has required invasive procedures with associated risk. New DNA sequencing technologies have now truly revolutionized the field.
Less than a decade ago, women seeking prenatal genetic testing, such as for a condition like Down syndrome, had to undergo invasive procedures to get a fetal DNA sample. These procedures (such as amniocentesis and chorionic villus sampling) also posed a low risk to the pregnancy itself.
The advent of highly sensitive and efficient methods for DNA sequencing has allowed a totally new approach for prenatal genetic testing, at least for the initial screening test for a new pregnancy. Specifically, these new methods allow the detection of the very small amounts of fetal DNA that naturally circulates in the mother's blood during pregnancy. Pregnant women now have the option of getting a new type of prenatal genetic test, one that doesn't pose a risk for miscarriage. It involves a simple blood draw from the pregnant women. This is called cell-free fetal DNA testing, or more commonly, non-invasive prenatal testing (NIPT), and it can be performed very early in the pregnancy. The uptake of NIPT around the world has been remarkable, with literally several million pregnant woman getting this test each year. However, it is important to know that the American College of Obstetrics and Gynecology strongly urges that that other tests should be used beyond the initial NIPT before any decisions about a pregnancy are made.
After their second pregnancy ended in miscarriage, Dan and Talia grew concerned that they might have serious genetic risk factors that would affect future pregnancies. They chose to have NIPT during their third pregnancy, and were relieved that the test performed with Talia's blood sample did not reveal any chromosomal abnormalities in the growing baby. They went on to have a healthy baby boy. Stories like theirs are becoming more common thanks to advances both in genomic technologies and in improving access to care. Dr. Diana Bianchi, the director of the NIH's Eunice Kennedy Shriver National Institute for Child Health and Human Development, said in 2017 that "just like Google or Airbnb changed how research and booking a room works, noninvasive prenatal genomics is altering the obstetrician profession around the world."
Mothers who have noninvasive prenatal genetic testing may not realize that it can also reveal things about their own health. That's what happened to Marin Mejia, who had NIPT while pregnant with her daughter Owen. She and her doctors discovered from NIPT that Owen did not have any chromosomal abnormalities. But the test also showed that Marin had cancer, which had spread to several organs. The NIPT detected cell-free DNA from Marin's tumor cells, just like circulating tumor DNA tests developed in recent years (see Cancer Genomics). Marin's medical team monitored her condition carefully, and delivered Owen two months early so that Marin could have cancer surgery and begin chemotherapy. In hers and other cases, the availability of NIPT allowed the medical team to prepare for treating both the mother and the baby.
Like many new technologies, NIPT is generating significant discussion about its ethical implications. Such prenatal testing is mainly used to detect an abnormal number of chromosomes, such as a trisomy. Down syndrome is a trisomy of chromosome 21, and NIPT for detecting Down syndrome and other chromosomal abnormalities is being widely implemented in some health systems (for example, the National Health Service in the United Kingdom). Since about 50 percent of Down syndrome children have heart defects, NIPT can be helpful by giving notice to the pediatric team, who may need to plan for surgery soon after birth. Parents can also begin to prepare for raising a child with Down syndrome or any genetic condition detected by prenatal testing.
However, because NIPT can be performed early in pregnancy, some parents might choose to terminate a pregnancy based on the results. This has led some advocates to question whether conditions like Down syndrome might eventually be eliminated from the population or whether parents who choose to have children with trisomies will face future discrimination. The Nuffield Council for Bioethics, based in the United Kingdom, has also raised concerns that NIPT might be used for selective termination solely based on the sex of the baby. With future advances in genomics technologies, it is likely that we will be able to detect other genetic conditions very early as well. With this will come the need to continue thoroughly considering the ethical implications of such new prenatal testing opportunities.
A quick internet search and conversation with your healthcare professionals can provide options for those seeking further information about NIPT. The National Institutes of Health has also started a new project called PregSource that aims to learn about the pregnancy experience. Share your experiences during pregnancy and after giving birth to help improve care. They also have a resource library to learn more.
Posted: April 17, 2018