Chapter Two opens with two scenes from a couple’s first prenatal visits, shares how we received an unconsented-to false negative screen, and, then discusses some of the common reasons couples seek prenatal genetic testing. (You can catch up with all of Chapter 1, here). Feel free to leave a comment about your own initial experience with prenatal genetic testing and whether I’ve fairly summarized the common reasons parents agree to prenatal genetic testing.
Scene I: An obstetrics practice examination room. Cramped, bathed in bright fluorescent light. The mother is on the examination table. The father sits in a chair by her side. A nurse enters carrying a basket with the supplies for taking a blood draw along with a manila folder with forms in it.
Nurse: Good morning. I see that this is your first appointment and you are estimated at nine weeks pregnant. How are we feeling?
Mom: Fine, actually. Surprisingly, no morning sickness aside from a little queasiness.
Nurse: Well, that’s good to hear. Now, with this being your first appointment, we need to take a blood draw and you and your husband should review these forms.
Dad: What are the forms for?
Nurse: These are consent forms for screening your wife’s blood for certain conditions.
Mom: Like what?
Nurse: For now, certain conditions that she or you could be a carrier for?
Dad: What kind of conditions and what do you mean by “carrier”?
Nurse: There are certain conditions that a parent can be a carrier for, not having the condition itself, but could be passed onto the child. In your all’s case, seeing from your pale complexion, Dad, you could be a carrier for cystic fibrosis, a condition more common among people of Scandinavian origin.
Dad: I’m familiar with Boomer Esiason’s son having CF, and a high school friend’s sister has that, but what is it?
Nurse: It’s a condition that effects the child’s lungs, causing the child to be unable to break down the mucous, and results in a shortened lifespan.
Mom: What will the carrier test tell us?
Nurse: If it comes back positive, then we’ll test Dad to see if he’s a carrier, since the odds of having a child with CF increase if both parents are carriers. Also, it would be good to know if one or both of you are carriers if you decide to get pregnant again.
Dad: I see that this consent form is also for genetic conditions?
Nurse: Right. If you all want, you can have your pregnancy screened at a later visit for certain genetic conditions like Down syndrome.
Mom: And, what would we do with that information?
Nurse: If it came back positive, it would allow you time to decide if you wanted to continue the pregnancy.
Dad: There isn’t any treatment available for Down syndrome is there?
Nurse: No.
Mom: So, with a positive test, we could decide to abort or not?
Nurse: That’s right.
Mom: Well, we planned on having this pregnancy and we’re not planning on terminating it.
Dad: Where do we sign if we want the carrier testing, but not the genetic testing?
Nurse: Right here. [The parents sign accordingly]. Okay, ma’am, please stick out your arm.
End of scene.
Scene II: Same couple are at a later prenatal visit when the pregnancy is at 11 weeks. This time they are in the ultrasound examination room. The ultrasound tech has applied the jelly to the mother’s abdomen and is starting to run the wand over her stomach to begin the examination.
Dad: This is different than the exam at 9 weeks, where we just saw a little bean of our baby.
Tech: Yes. This time, your baby will look more like a baby. You’ll get to see the baby’s head, hands, arms and legs, provided the baby is in the right position for viewing.
[The “wub, wub, wub” of the sonar fills the silence in the room as the parents wait with baited breath].
Mom: Oh, there’s our baby!
Tech: Your baby is in a good position. See, here’s the head … now those are the fingers … you can even make out the foot.
[Mom openly tears up; Dad quickly wipes away any welling up of his eyes].
Tech: Your baby is looking good.
[wub, wub, wub]
Tech: The neck is measuring fine.
Dad: What does that mean?
Tech: Oh, there’s some research that shows there’s an association between the thickness of the neck and Down syndrome.
Dad: What does “the neck is measuring fine mean”?
Tech: It means it’s not measuring in the range associated with Down syndrome.
End of scene.
If you hadn’t guessed it already, those were our first two prenatal visits. The first scene reflects the extent to which we were counseled about prenatal genetic testing. The second scene reflects the ignoring of our declining of prenatal testing for Down syndrome, with the ultrasound tech giving us an unconsented-to false negative, since we would learn postnatally that Juliet most definitely had Down syndrome.
The first scene also reflects the common decision protocol that many parents go through when considering prenatal testing. As you’ll read later, for our first pregnancy, which we had read a book about to maximize chances of conception, this was a wanted and planned pregnancy. Therefore, when the offered testing did not provide any prenatal treatment, we did not see the use of it.
While our decision matrix is one many other parents use, it obviously isn’t the only one. Increasingly, for reasons explained towards the end of this chapter when discussing NIPT (a term defined (and debunked) later), more and more women are accepting prenatal testing for the purpose of receiving reassurance. It is estimated that only three percent of all pregnancies have what the March of Dimes refers to as a “birth defect.” But, that figure encompasses the full range of conditions a child may be born with, from cleft lip and palate (a condition my twin brother was born with) to genetic conditions like Down syndrome. The latter, genetic conditions, make up an even smaller percentage. Therefore, statistically, most pregnancies are unaffected and a negative prenatal test result offers some reassurance to expectant parents.
Further, at an increasing rate, mothers and couples are accepting prenatal genetic testing in order to prepare for the birth of their child. After all, we have been living in the “information age” for decades, and “information” has become a sought after commodity. With the opportunity to find out earlier than ever whether your child is affected by a condition, more parents are opting into prenatal testing so that they can decide whether to continue their pregnancy and, if so, plan for and prepare their loved ones and medical team for the delivery of a child with a condition.
Still more, there are those families who know there may be an increased chance for having a child with a condition. From the prenatal care scenes described above, those of Scandinavian origin either already know or will likely be counseled by their providers of the increased chance for being carriers of CF. (Not that it matters, but as near as my mother’s genealogical sleuthing can tell, we are of Irish and French stock; but I am closer to Jim Gaffigan on the pigment scale, so the nurse can be forgiven for presuming I’m a descendant of Vikings). For these families, knowing they already have an increased chance for a condition, prenatal testing offers them even greater reassurance with a negative result and time for deciding, planning, and preparing should they receive a positive result.
This is not an exhaustive list of all the reasons why parents choose or decline prenatal testing. But, these are some of the most common reasons and are shared to keep in the background throughout this book for considering whether prenatal genetic testing is providing what families are seeking. What follows now is an overview of the most common methods for prenatal genetic testing, told in the chronological order of when they were introduced into clinical practice.
Tune in next week for the first part of Chapter 2’s description of diagnostic testing.
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