Week 9: Prenatal Testing For Baby

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This is your Pea in the Podcast for week nine of your pregnancy. I'm Bonnie Petrie joined again by Dr. Laurie Swaim, an obstetrician with Houston Women's Care Associates in Houston, Texas.

At nine weeks along it's time to start thinking about what kind of prenatal testing you're interested in because over the next several weeks you'll be offered several different batteries of tests. Prenatal tests include: blood tests, ultrasounds and sometimes invasive testing that will take a bit of tissue or amniotic fluid and it can help identify and sometimes treat health problems that could endanger both you and your baby. But Dr. Swaim says not everyone wants testing, "There are some people who feel very strongly they want testing and some who don't and some who would accept testing as long as there's 'no risk' and some who will want every test even though they don't necessarily fall into a risk category."

So what do prenatal tests look for and why wouldn't everyone want them? Well they look for several things, first you're tested for treatable health problems you may have that could affect your baby's health and tests like ultrasounds look at the baby's characteristics including size, sex, gestational age, and placement in the uterus. Other prenatal tests measure, as well as any test can, the chance that a baby has certain congenital, genetic or chromosomal problems and they look for certain types of fetal abnormalities too including heart problems. All this information about the little person growing inside of you can help you prepare for their birth particularly if they may have special needs and sometimes, sadly, if a baby has a problem that is incompatible with life meaning they will likely die at some point during the pregnancy or soon after birth or maybe a problem that will greatly impact the child's quality of life. Some women will use the information gained through prenatal testing to decide whether they want to continue their pregnancies. So why wouldn't you want this information if it helps you to know and prepare for the baby that's on the way? Well, two of the tests offered come with some chance of miscarriage and some moms to be don't want to risk it; we'll talk more about that in a minute. Other moms-to-be shun any information saying it will have no influence on their decision-making process with regard to the coming baby. That is completely up to you.

Okay, let's talk about your options as far as prenatal testing goes. First there are the tests that have no risk of miscarriage, "The traditional screening tests used to be called the quad screen years ago it was the triple screen and that's a blood test that can be done between 16 and 26-7 weeks it's most accurate between 16 and 18 weeks. That test will detect somewhere in the order of 75% to 80% of babies with Down syndrome and a higher percentage of babies with spin bifida. The newer test is called a nuchal translucency which is combined with blood tests on the same day, so it's a first trimester screen. It's done between 10 and 13 weeks so there's that window of opportunity and there's only really a handful of people at least in this city and probably every major city who are trained to do it and people should not be doing it unless they've had adequate training. Part of that, although it doesn't seem like it would be hard to measure the distance of the babies thickness of its neck, it's somewhat technically challenging, the baby's head has to be in a certain position and what have you." Now you may be offered the nuchal translucency over the next couple of weeks. Some women will rely on this test to help them decide if they want another test that's only available only over the next couple of weeks as well. It's called the CVS. The CVS is invasive and it does carry some risk of miscarriage. First let's talk just a bit more about the nuchal translucency, "The advantages of having the earlier screening are first of all it's more sensitive, it will detect about 90% of babies with down syndrome or other chromosomal rare problems like trisomy 18 and so it's a little bit better. Also, if abnormal, the results are back earlier therefore it will enable a woman to have a CVS if she chooses to do so. The CVS does have a higher risk to the amino so in general we don't offer just anyone a CVS who is of young age, although certainly if someone really, really wanted one and she understood the risks that would be her business. So some women are using it to help them decide if they want an earlier evasive test. Some women are using it just as the only test they have and you know if they're happy with 90% then that's fine, that's up to them, that's their business." Now about one woman in 360 who have the CVS will have a miscarriage and though that's smaller than previously thought the number is too high for some moms-to-be to take. The benefits of this first evasive prenatal test available to you are that you will get some definitive information about your baby's health including if they have any of hundreds of inherited diseases such as Tay Sachs disease, hemophilia or cystic fibrosis. The CVS will also find chromosomal defects such as Down syndrome and it will tell you if your baby is a girl or a boy.

Now you can find out about all of this information as well with the second evasive test available to you, the amniocentesis. Who's offered this test? "We used to categorically offer all women who were going to be 35 or 34 at delivery some form of evasive testing usually in the form of amniocentesis to determine if the baby has Down syndrome or another chromosomal rearrangement problem. The reason that we did that is because the risk of the amniocentesis is off quoted as about somewhere between 1 and 200 and 1 and 280 and the risk of a mother at that age having a baby with down syndrome is greater than the risk of the amnio. Things are changing now because we now know amniocentesis carries much less risk than we used to quote, much less, it's probably more in the order of 1 or 500 or even lower. So now amnio really could be offered to any woman. And the majority of babies with Down syndrome were born to women who were less than 35 and that's just because the majority of women less than 35 are having babies. So we see women day-in and day-out and they say 'well I have no risk', well you might not have any risk but guess what, it can happen to you."

In addition to older moms-to-be, who else might consider evasive prenatal testing? A woman who's had a premature baby or has had a baby with a birth defect, especially a heart or genetic problem. A woman with high blood pressure, diabetes, lupus, asthma or a seizure disorder might consider invasive prenatal testing or a mom-to-be who has, or has a partner who has, an ethnic background in which genetic disorders are common. Also parents who have family history of mental retardation may consider invasive prenatal testing. Now for a woman who's not interested in invasive prenatal testing, Dr. Swaim says there are a couple of different ways to handle your blood testing to get more sensitive results, "Besides the first trimester screen, there's something called the Integrated screen where you get the first trimester information and then draw the blood at 16 or 17 weeks for a quad screen and all that information is integrated together and you have an even more sensitive test. The advantages of that is it's a few points more sensitive, a lot of specialists and obstetricians do not feel that it's sensitive enough to warrant waiting for the results for another three to four weeks but some do. You can also sequentially screen whereby you have the first trimester test and then you get the results and then you have the second trimester test and you get the result. So you see the difference is that you only get one result with the integrated screen and you have to wait for it. And some women don't want to wait because it makes them nervous."

Now if you decided the nuchal translucency, with it's first trimester screen, is the only prenatal testing you want, your doctor will probably ask you to consider one more blood draw a little later in your pregnancy, "It's still recommended that she have a portion of this quad screen called the MSAFP, it stands for Maternal Serum Alpha-Fetoprotein, between 16 and 18 weeks, because that's the test for spin bifida and none of that can be tested in the first trimester blood or ultrasound."

Are you confused yet? Your doctor should be able to help you more. Dr. Swaim says they'll talk you through it, "The other thing that we do in our office is we have a great print out of information about those because it is confusing and so we give it to all our patients so that way they know. Some know, some say 'yes I want the test', okay fine so we'll go ahead and you get the ball rolling to schedule it and other people want to think about it." Now some women will feel pressured not to have prenatal testing even though they might want to because there is a misconception that someone who consents to testing is doing so only because they will terminate their pregnancy if they find out something's wrong. While this is certainly true occasionally, many moms-to-be get the testing because they want to know their baby better and they want to be prepared. Some parents find having time to prepare for a coming special needs baby makes them better parents to that special child from the beginning. Let this be your decision, either way.

So what is your baby like in there this week? "It probably looks on an ultrasound like a big gummy bear at eight weeks and by nine weeks its limbs are a little bit longer. It looks like a human but just really small with a big, big head." And in fact its head is nearly half the size of its entire body and it's started dancing in there too. While you will be able to note that movement on an ultrasound if you had one this week, you won't feel it for another 10 more weeks give or take, particularly if this is your first pregnancy. Now the nerve connections from the retna to the brain are being established now for the baby. Also your baby's neck is beginning to appear. Your baby's skeleton has started to form cartilage and bones are taking shape and guess what? You have a boy or a girl in there now, while you still won't be able to determine gender on an ultrasound quite yet the internal reproductive organs are well in place and perfecting themselves.

Well how about you? How are you doing this week? "She's probably not feeling much different if she had nausea, she probably still has nausea, she's probably still tired, she probably still has breast tenderness, she may still have constipation, and she's not going to look any different other than tired and nauseous and remember once again the majority of women aren't really nauseous when they're pregnant. Lots of women may think that their stomach is starting to pouch out but their uterus is still so small that it's in the bony pelvis and so there's no way that she's showing at this time." But you still may be a little bloated at the waistline and your jeans may remain a bit snug, you're not ready though for your new pregnancy wardrobe just yet. Don't worry it's coming soon enough. You're nine weeks pregnant; you have 31 weeks to go until week 40.

That's your Pea in the Podcast for week nine of your pregnancy. Dr. Swaim and I look forward to talking with you again next week. Enjoy this week, we'll see you then. I'm Bonnie Petrie, thanks for listening.