How prenatal genetic screening can identify more conditions during pregnancy
September 22, 2026
For more than a decade, noninvasive prenatal testing (NIPT) has helped expecting parents learn more about their baby’s health early in pregnancy with a simple blood draw from the pregnant person.
NIPT has traditionally screened for chromosomal conditions caused by an extra or missing chromosome, such as Down syndrome (trisomy 21) or Turner syndrome. A newer form of testing, called single-gene NIPT, builds on traditional NIPT by screening for certain conditions caused by changes in individual genes.
Chromosomes are only one level of genetic information. Within each of our 46 chromosomes are between about 50 and 3,000 individual genes, and changes within a single gene can also cause genetic conditions.
Think of the genome as a book with 46 chapters. A chromosomal condition might be like having an extra chapter or missing one. Single-gene testing looks much more closely – reading the individual letters within the words to spot a genetic “misspelling.”
Until recently, we could not screen a pregnancy for very many single-gene conditions through a pregnant person’s blood. Scientific advances are changing that. Today, single-gene NIPT allows us to screen for changes involving nearly 200 genes, and that number is growing quickly.
For some families, receiving single-gene data during pregnancy can provide reassurance. For others, it can help determine whether additional testing is appropriate or help the care team plan for pregnancy monitoring, delivery, and care after birth.
But single-gene NIPT has some limitations. It is not one universal test that checks every gene or genetic condition. And like traditional NIPT, it is a screening test and not a diagnostic one.
Think of the genome as a book with 46 chapters. A chromosomal condition might be like having an extra chapter or missing one. Single-gene noninvasive prenatal testing (NIPT) looks much more closely – reading the individual letters within the words to spot a genetic “misspelling.”
Heather Fisher, M.S.
What single-gene NIPT can and can’t tell us
NIPT analyzes small fragments of placental DNA that circulate in a pregnant person’s blood. The test can be done as early as 10 weeks of pregnancy. Because it requires only a blood draw, it is considered noninvasive.
Single-gene NIPT applies increasingly sophisticated technology to look for specific genetic changes associated with certain conditions. However, it will not provide a diagnosis. A high-risk or positive result does not mean that your baby definitely has a specific condition. False-positive and false-negative results are possible.
If the test shows low risk
A low-risk result can be reassuring, but it does not eliminate the possibility of a genetic condition. The information can still be very valuable.
If the test shows increased risk
If a screening result indicates an increased chance for a genetic condition, that might change how closely we monitor the pregnancy, what we prepare for at delivery, or what specialists should be available after birth. We will discuss whether you want to do diagnostic testing with chorionic villus sampling (CVS) or amniocentesis, which can provide a more definitive answer during pregnancy. CVS analyzes a sample from the placenta, and amniocentesis collects fetal cells from the amniotic fluid around the baby. Some families may instead choose additional testing after the baby is born.
In a small but growing number of conditions, prenatal diagnosis may create opportunities for treatment before birth. Cystic fibrosis (CF) is one example. Researchers are beginning to explore therapies that could potentially treat CF before birth, though this is still an emerging area of medicine.
Carrier screening is an important first step
Carrier screening helps estimate the chance that a child could inherit a genetic condition from you or your partner. Some of the conditions we can screen for include sickle cell disease, cystic fibrosis, or spinal muscular atrophy (SMA).
A carrier has a genetic change associated with an inherited condition but usually has no symptoms. Most carriers are healthy and have no known family history of the condition, which is why you can’t assume you aren’t a carrier simply because a condition doesn’t run in your family.
If carrier screening shows that one parent is a carrier for a recessive condition, such as cystic fibrosis or sickle cell disease, carrier screening is available for the other biological parent. If both parents are carriers for the same recessive condition, each pregnancy has a 25% chance of being affected.
Single-gene NIPT doesn't replace carrier screening. In some situations, carrier screening helps determine whether single-gene NIPT might be useful. Another common scenario is when a patient learns through carrier screening that they are a carrier, but the other biological parent cannot or does not complete testing. Single-gene NIPT may be able to provide additional information about the pregnancy rather than having to wait until the baby is born.
3 situations in which we might consider single-gene NIPT
The expanding number of genes that can be screened for generally falls into three categories.
1. Recessive genetic conditions
For recessive conditions, a child generally must inherit a disease-causing genetic variant from both parents to have the condition. Single-gene NIPT is now available for a growing number of these conditions, including cystic fibrosis, sickle cell disease, and alpha and beta thalassemia.
We most commonly consider this testing after carrier screening has identified one or both parents as carriers. It may be particularly useful if both biological parents are known carriers but want additional screening before deciding whether to pursue CVS or amniocentesis, or if the other biological parent cannot complete carrier screening.
2. Dominant genetic conditions
For a dominant condition, a change in just one copy of a gene can cause the condition. Sometimes that genetic change is inherited from a parent who has the condition themselves. Other times, it occurs for the first time in the baby, meaning neither parent has the condition.
One reason we might consider single-gene NIPT is if an ultrasound shows something that could be associated with a particular dominant genetic condition. For example, ultrasound findings might raise concerns about skeletal dysplasia or Noonan syndrome, which affects development in various parts of the body.
Single-gene NIPT may give us more information about the chance that your baby has one of these conditions. We also might consider this testing when the biological father has a known dominant genetic condition.
This brings up an important limitation: If the pregnant person has a dominant genetic condition, single-gene NIPT generally cannot distinguish the parent’s genetic variant from the baby's because both are present in the pregnant person’s blood sample.
3. Red blood cell and platelet antigen status
The third application is a little different. Single-gene NIPT can help us determine certain red blood cell and platelet antigens a fetus has inherited.
Antigens are proteins on the outside of blood cells. If a pregnant person and her baby have different red blood cell antigens, the pregnant person’s immune system can sometimes develop antibodies against the blood cells of the fetus. This can cause serious complications, including jaundice and hemolytic disease of the fetus and newborn (HDFN), a serious form of fetal anemia.
Many people are familiar with one version of this condition: Rh-positive and Rh-negative blood types. We routinely give Rh-negative pregnant patients a medication called RhoGAM to prevent the development of antibodies against the Rh(D) antigen. RhoGAM prevents any development of complications or HDFN during pregnancy in an Rh-negative pregnant person. But there are other, rarer blood cell antigens for which we do not have the equivalent of RhoGAM.
In these types of pregnancies, determining the baby’s antigen status through a maternal blood sample can help us decide how closely the pregnancy needs to be monitored and tailor care during the pregnancy.
Genetic tests are only part of the picture
One of the most important things I tell patients is to never interpret genetic screening results in isolation. We always look at the result alongside ultrasound findings, the parents’ medical histories, and the family's health history. Sometimes that additional information significantly changes how we understand a result.
For example, I once counseled a family whose single-gene NIPT result indicated an increased chance for osteogenesis imperfecta, a genetic condition associated with brittle bones. Understandably, the family was worried. Further evaluation showed that the baby’s father had the same genetic variant. He had never been diagnosed with osteogenesis imperfecta and had experienced only a few fractures throughout his life. That additional family history helped us better understand what the baby’s result might mean.
That’s why talking with a genetic counselor can be helpful. Genetic counselors help families understand what a test can detect, what it cannot, how reliable it is for a particular condition, and how the results fit with everything else we know about the pregnancy.
Single-gene NIPT is advancing quickly. We can screen for far more conditions today than we could just a few years ago, and the list continues to grow. But more information isn’t always helpful for every family, and single-gene NIPT isn’t necessary in every pregnancy.
Talk with your Ob/Gyn, maternal-fetal medicine specialist, or genetic counselor about the benefits and limitations of the screening available to you. Together, we can determine which information will be most useful for your pregnancy.
To talk with an expert about single-gene NIPT, make an appointment by calling 214-645-3838 or request an appointment online.
