Dr. Bob Underwood (Host): Welcome to Pediatrics in Practice, a CME podcast. I'm your host, Dr. Bob Underwood. Before we introduce our guests, I'd like to remind you to claim your CME credits after listening to today's episode. You can do so by visiting cmkc.link/cmepodcast and click the Claim CME button.

Now, today we have an expert in prenatal genetic testing from Children's Mercy, Lylach Haizler-Cohen. We're discussing prenatal genetic testing and how pediatricians can use genetic testing while caring for patients and families. Dr. Haizler-Cohen, welcome to Pediatrics in Practice.

Dr. Lylach Haizler-Cohen: Hi. Thank you for having me today. It's a pleasure to be here.

Host: Yeah. So, this is really advanced and exciting stuff that we're talking about. So, why don't you start us off with just telling us what are some of the most common types of prenatal genetic tests—like cell-free DNA, microarray and exome—and what should pediatricians understand about what these tests can and cannot tell us when we're caring for patients?

Dr. Lylach Haizler-Cohen: Sure. So, prenatal genetic testing can be divided into two main categories. The first one is genetic screening, and this tests for the baby's risk of having genetic condition, whether it is high-risk or low risk. The second category is diagnostic testing, and this evaluates whether the baby is actually affected with a genetic condition.

The most common type of prenatal genetic screening test that we use is NIPT or non-invasive prenatal testing. This looks for the cell-free DNA that is circulating in the maternal blood. We know that most of this circulating cell-free DNA is from maternal origin, but there is a small portion that is of fetal origin. So starting 10 weeks of pregnancy, there is enough fetal fraction for us to be able to evaluate the baby. The standard NIPT looks for a limited number of common genetic conditions like Down syndrome, which is trisomy 21, trisomy 18, trisomy 13, and the sex chromosome aneuploides like Turner syndrome or Klinefelter syndrome.

There are other NIPT platforms that can look for other genetic conditions like microdeletions. An example would be 22q11.2 deletion syndrome or DiGeorge. Others look for single gene disorders like cystic fibrosis or sickle cell disease. And then, other platforms look for larger deletions or duplications genome-wide that are more than seven megabases.

To understand what is the difference between the different types of genetic testing that we can do prenatally, I like to think of the DNA as a library of the instructions in our bodies. If you go to the library, you can see books around you. And in the books, there are chapters and those chapters have sentences. So for a archetype, we're looking around the library and we're looking to see if there's any extra books, missing books or something obvious like a book that is missing a cover. A microarray goes into more details, looking at the chapters of each book. So, this can find more subtle deletions or duplications in the DNA. And finally, exome sequencing looks at the spelling of the sentences in the book and can find any typo in the DNA. This makes it pretty clear why karyotype is going to miss many of the genetic differences that may be underlying congenital anomalies.

So, karyotype and microarray are looking at the amount of DNA and exome sequencing is looking at the spelling of DNA. For sequencing, there's also different types of tests that can be ordered. Gene panels look at the specific spelling of genes that are related for a specific fetal condition, like a skeletal dysplasia or Noonan syndrome or holoprosencephaly.

Exome and genome sequencing are more comprehensive genomic tests. Exome sequencing looks at 1-2% of DNA that is coding for protein. And genome sequencing looks at the entire DNA, also the non-coding regions. When we're ordering exome or genome sequencing, the ideal situation is to have a trio sample. So to have a sample from both the baby and the parents. If we know that the parents are healthy and we find a genetic change in the baby and in one of the parents, we wouldn't expect that genetic change to be the reason for the differences we're seeing in the baby. In prenatal diagnosis, we consider exome and genome sequencing, the most comprehensive testing that is available today.

Host: So, one of the things that I think we talked about earlier is just how advanced this has gotten and how fast it's getting advanced. So when a family comes in for their first newborn visit, with prenatal results in hand, what are the key questions that a pediatrician should ask to quickly assess what followup might be needed for this newborn?

Dr. Lylach Haizler-Cohen: So, there are a few important questions that a pediatrician can ask. First, it's important to clarify whether these results come from a screening or a diagnostic test. If the findings are from a screening test, like NIPT, the pediatrician should ask whether diagnostic confirmation was performed. And if it wasn't performed, postnatal confirmation is necessary.

Next, it's important to understand what is the prenatal testing that was done. For example, was it done for advanced maternal age, for abnormal ultrasound findings, or was it done for a family history of a genetic condition? The pediatrician should try to review the specific result and, if possible, the actual testing report. Specifically for microarray or exome sequencing, it's also helpful to determine whether the variant was pathogenic or likely pathogenic, or was it a variant of uncertain significance, because we look at those results very differently.

It's also important to assess what counseling the family has received so far. Have they been informed on the natural history, the prognosis, the treatment options, the surveillance recommendations, and the recurrence risk for future pregnancies. And, finally, based on the results and clinical context, the pediatrician should also help coordinate the referrals with specialist followup as needed to ensure that the family has a clear plan of care.

Host: Now, you just mentioned variants of uncertain significance, and those are increasingly common. So, should a primary care clinician explain a variant of uncertain significant or VUS to a family in any particular way? And what's the appropriate approach to followup on a referral?

Dr. Lylach Haizler-Cohen: So, variants of uncertain significance are very difficult to navigate, both for providers and for patients. A variant of uncertain significance or a VUS is a genetic change for where there isn't really enough evidence to classify it as either pathogenic or benign. In other words, we just don't know whether these genetic changes are just normal human variations from one person to another, or are they actually disease-causing.

Over time, interestingly, most of the VUSs are actually reclassified as benign. So, it's important to emphasize that the medical management and the surveillance for the baby should actually not be altered solely based on a variant of uncertain significance. And many laboratories don't even report VUSs prenatally, because of the difficulties with interpretation and the confusion it can cause for parents.

After birth, a VUS can be reported by the lab if it is requested by the provider. After the baby is born, there could be additional clinical information about the baby's phenotype that sometimes can help the lab clarify the significance of the variant. So, I would say important for pediatricians, when a vose is identified on prenatal testing, it's recommended to refer to the family to a medical geneticist for expert interpretation, and also to ensure that appropriate phenotyping has been completed for the baby.

The followup for VUS generally involves just periodic reanalysis by the laboratory because, as new research and clinical data become available, sometimes it does help the lab reclassify these variants of uncertain significance.

Host: It really is kind of amazing how much information we can get from genetics and we're still learning what is a VUS and what may not be in the long run. And so, you're right, a lot of that will just add uncertainty or confusion to parents if they don't know whether or not it's significant or not. And I think that that's really important, and even to pediatricians who may be unfamiliar with prenatal genetic testing for the kids that they're taking care of.

So with that being said, how should pediatricians prioritize which prenatal findings require immediate postnatal testing, like confirmatory labs, imaging, specialty referral, things like that versus results that can be monitored over time? How should a pediatrician prioritize that?

Dr. Lylach Haizler-Cohen: So, prioritizing really depends on whether the suspected genetic condition in question actually poses an immediate risk for the newborn. And many of these severe conditions are actually included in the newborn screening. So, a classic example is a newborn with atypical genitalia where we are suspecting congenital adrenal hyperplasia.

We all know that with the classic form there is impaired production of cortisol and aldosterone, and that could lead to life-threatening salt wasting crisis. So, these infants traditionally need very emergent evaluation of the electrolytes after birth. And if adrenal hyperplasia is suspected, they need replacement therapy with glucocorticoids to avoid that adrenal crisis.

Another example of a high priority category with genetic conditions are disorders of metabolism. We know that many of these conditions place newborns at-risk for rapid decompensation after birth, even with brief fasting or physiologic stress. And early signs can be immediately noticeable, infants showing up with hypoglycemia or acidosis or altered mental status. So when a prenatal diagnosis of an inherited disorder of metabolism is present, or a strong clinical suspicion exists, the infant should be evaluated immediately by a biochemical geneticist, and their input is helpful for many things—to guide laboratory testing, fetal feeding plans, and emergency management protocols.

In contrast to those situation, there are other findings that don't necessarily pose an immediate physiologic risk to the newborns. So, things like carrier status or variants of uncertain significance or mild structural differences without functional compromise, and those can usually be monitored over time with close followup and appropriate specialty referral as needed. Ultimately, the guiding principle is not how significant a diagnosis sounds, but rather whether an early intervention can prevent acute harm in the neonatal period.

Host: When we started our questions, you mentioned a couple of high-impact scenarios. For example, positive cell-free DNA screening for trisomy 21, or a microarray finding of a 22q11.2 deletion. Can you explain some of the first steps that a primary care provider should take after birth if these are the high-impact scenarios that they're running into?

Dr. Lylach Haizler-Cohen: Absolutely. And these are exactly the situations where a primary care pediatrician can actually make a huge difference in those first days of life. So, a cell-free DNA, that was high-risk for trisomy 21 in a pregnancy and did not have confirmatory testing during pregnancy needs to first of all be confirmed postnatally. And this is typically done with a FISH and a karyotype.

A FISH can actually give us a very quick preliminary result within 48 to 72 hours. The baby should also be thoroughly examined after birth for the common dysmorphology that we would expect with trisomy 21. The exam should also include evaluation for things like hypotonia, feeding difficulties. If a murmur is present, that could suggest a congenital heart disease, and then any respiratory concern. Specifically for trisomy 21, we should also order an echocardiogram because we know that 50% of those babies can have congenital heart disease. Also important to check is third screening, hearing evaluation, and feeding and tone assessment.

Then, for the baby that presents with 22q11.2 deletion syndrome or known as DiGeorge syndrome, there are other important clinical evaluations that should take place. Those include immune function, evaluation, checking calcium levels, because these babies can have hypocalcemia. It's important to take a look in the mouth and to evaluate whether there is a cleft palate, because those babies are at increased risk for these cleft palates, and that could lead to feeding difficulties. And then, also, these babies should have an echocardiogram because of the association with conal and truncal congenital heart disease.

Host: So, a lot of this is really new. And parents are likely to be worried, confused, or misunderstanding even the meaning of some of these genetic testing. So, what are some communication strategies that help pediatricians navigate conversations with parents when they come in not really understanding the full meaning of these results?

Dr. Lylach Haizler-Cohen: So, there are several communication strategies that I typically use, and I also see commonly used by genetic counselors. And I think those can be very helpful for pediatricians who are navigating these sensitive conversations.

So first of all, it's essential to assess the parents' understanding of what's going on. So using open-ended questions like, "Can you share with me what you were told about these results? Or what are you most worried about right now?" Questions like that can help uncover misunderstandings and parents, and also provide insight as to their emotional state. Families often arrive to us with partial information or assumptions that need gentle clarification. If applicable, it's also important to clearly distinguish between screening and diagnostic testing, as we said, because many parents don't realize the difference between the two types of tests. And clarifying this can immediately reduce confusion and anxiety.

It can also be helpful to organize the discussion and to kind of three simple categories: What do we know about the condition? What don't we know about the condition? And what are we going to do next? This structure provides clarity to parents, sets expectations, and reassures families that we actually have a plan in place for them. Parents frequently experience, guilt, fear, self-blame when hearing about a possible or confirmed genetic condition. And using statements like, "Nothing you did caused this" or "It's completely understandable to feel overwhelmed," this can significantly reduce the distress and built trust with parents. Delivering the information in small, manageable pieces while pausing to check understanding with phrases like "Does that make sense?" can also really improve retention and engagement. Repetition can be helpful, especially in high stress moments.

And finally, ending the conversation with the clear plan, and that includes the specific next steps, the timeline, and a schedule for followup. All of those can greatly reduce the anxiety and help families leave feeling supported.

Host: Yeah, I think that that's really, really, really important because This is going to be a stressful time for parents when they have these kind of results and they really don't understand them, and your mind for new parents is already at a position of worry. And so, I really think it's up to the clinician, to the pediatrician to help settle a lot of that concern that they may be having.

So as prenatal testing becomes more sophisticated, what are the emerging trends? We mentioned earlier it's advancing fast. So, what trends should pediatricians be aware of and how might this change what happens in the newborn or early infancy period as we see these things come to fruition?

Dr. Lylach Haizler-Cohen: So as the cost of exome and genome sequencing continue to decline, we are expecting to use these technologies more frequently, and not only in pregnancies with fetal anomalies, but also in pregnancies that are uncomplicated just by maternal request. And this broader use will inevitably lead us to more findings and more complex findings that would be difficult to interpret.

One of the major trends will be findings of variance in genes with variable expressivity and reduced penetrance. So, what I mean is that we can find genetic changes that may or may not cause symptoms for the baby. And when they do cause symptoms, the severity can also range from mild to severe. We are also likely to see more prenatal findings and genes that are associated with neurodevelopmental conditions without findings on ultrasound. And these diagnosis often don't have clear manifestations in the newborn period. So, this may place pediatricians in a spot where there are guiding families through uncertainty, and also focusing on developmental milestones and referral for early intervention.

And then, finally, with this expanded use of exome and genome sequencing, we will also find more variants of uncertain significance prenatally. And these findings, as we said, can heighten the parental stress levels and, particularly, when we don't have a clear answer about the clinical implications.

Host: This is really exciting stuff and just quite advanced over a short period of time. Anything you'd like to add as we kind of come to a conclusion on some of these thoughts?

Dr. Lylach Haizler-Cohen: So just last thing to say, I am very interested in the genetic etiologies of different congenital anomalies. And I feel that even when using very comprehensive genetic testing, we're often left in a situation where we don't find an answer for the family. And many of these conditions are thought to be multifactorial. So, there are genetic and environmental kind of factors that play together to cause the anomaly.

I am specifically interested in looking at even more advanced genomic technologies. One of the technologies we're using at Children's Mercy. It is called long-read genome sequencing, and we are using this under the Genomic Answers for Kids program. And we're now trying to enroll pregnant patients and sending that amniotic fluid for this more comprehensive genetic testing to help us cover these variants that we're just not picking up with traditional genetic testing methods. So, I think we're at a very exciting time. And I'm really hopeful that we will be able to find more answers for these families that are really struggling to go through these pregnancies.

Host: Absolutely. Yeah. Thank you, Dr. Haizler-Cohen, thank you for being with us today. Really exciting advances. We appreciate you being on.

Dr. Lylach Haizler-Cohen: Thank you.

Host: Yeah. And as a reminder, claim your CME credits after listening to this fascinating episode today. You can do so by visiting cmkc.link/cmepodcast and click the Claim CME button. And if you enjoyed this podcast, please share it on your social channels and check out the entire podcast library for topics of interest to you. I'm your host, Dr. Bob Underwood, and this is Pediatrics in Practice, a CME podcast.