Making sense of the menu of prenatal testing options
Your baby may not be ready for the SAT, but their first tests happen before they exit the womb. And they aren’t the only one under the microscope. You’ll be treated to what feels like a never-ending battery of pricks, pokes, prods, and blood draws during pregnancy, too.
It’s easy to jump down a rabbit hole of things that could possibly go wrong, so here’s a reminder that most babies are born without any problems. Unless medically indicated, many of the testing options below are just that—options. You have full control over which tests are performed, and what information you receive. That said, unless you really hate needles (or peeing), there isn’t much downside to your tests, as most are noninvasive. Most practitioners will insist you keep up with blood panels each trimester, and require gestational diabetes and group B strep (GBS) screenings at a minimum.
The bigger decision is how much information you want about your growing baby. Prenatal testing looks for abnormalities that indicate developmental or physical problems. It starts with screenings that calculate the likelihood that the baby might have a condition, and progresses as needed to diagnostic tests that provide a definitive answer. If you have no family history, are low risk, and everything looks fine, you probably won’t be offered prenatal testing, though you can still opt in. If testing isn’t called for and you still want to do it, insurance seldom covers it.
Some couples choose to forgo testing entirely. Others want to know every detail. Most will at least do ultrasounds, if only to get their first peeks at the baby and to learn its gender. But prenatal testing isn’t perfect and can cause a lot of stress. There can be false negatives and positives, and diagnostic testing carries risks.
If you’re weighing what’s right for you, ask what you would do with the information you receive. Good news gives peace of mind. Bad news is more complicated. Knowing in advance that your baby will require special help or surgery at birth gives you time to plan, and in some cases the opportunity to manage conditions before the child is born. But you may be faced with decisions you never expect to make, like dealing with a result that reveals a severe or even fatal condition. If you know you would do nothing differently regardless of the results, testing may not be for you.
Don’t worry—you and your partner won’t navigate this process alone. Genetic counselors work with your provider to explain what’s happening, and help you interpret the results should you need it.
For many parents, the first ultrasound is when pregnancy starts to feel real, especially after showing friends and family your keepsake sonogram. But wait, isn’t a sonogram the same thing as an ultrasound? Though the words are sometimes used interchangeably, an ultrasound is the procedure itself, and the resulting photo is the sonogram.
Inspired by such disparate phenomena as echolocation in bats and the sound waves used to detect undersea obstacles after the sinking of the Titanic, ultrasound first entered prenatal care in 1956. Dr. Ian Donald of Glasgow was the first to use it in obstetric practice, but it didn’t catch on in the US for another twenty years.1 It’s now a standard of prenatal care around the world.
Ultrasound uses high-frequency sound waves to make images of the inside of the body. During pregnancy, the probe directs these sound waves through the cold gel on your stomach into your uterus. When the waves make contact with the fetus, they bounce back and create a picture. Ultrasound is used to make sure a baby is growing properly, to estimate gestational age, to check organ development and blood flow, and, of course, to discover the gender. Only two ultrasounds happen during a routine pregnancy—one in the first trimester and another in the second, known as the anatomy scan. If you are carrying multiples, have bleeding, or are considered high risk, more will be scheduled.
Before you get sad about the dearth of ultrasounds, remember that it is a diagnostic procedure, not a baby peep show. Skip the at-home Doppler to listen to your baby’s heartbeat. It can be easy to miss fetal movement and hard to find the heartbeat. Same goes for predicting whose nose she has with 3-D and 4-D ultrasounds. The risks of too much ultrasound exposure haven’t been studied, so minimizing the number you receive is best.
So what exactly are the risks of ultrasounds? At very high power, ultrasound waves can damage human tissue. We aren’t sure exactly how high, because it isn’t ethical to subject anyone to those levels for testing. What about radiation? X-rays and other medical imaging use ionizing radiation, which removes electrons from atoms and molecules. The nonionizing radiation used in ultrasound does not. When administered infrequently and performed in a medical context by a trained professional, ultrasounds are considered safe.2
Your first ultrasound usually happens between eight and ten weeks. It confirms the fetal heartbeat, checks dating, ensures the pregnancy is happening in the uterus (as opposed to the fallopian tubes, a dangerous condition known as ectopic pregnancy), and reveals if you are (surprise!) growing more than one human. This is the only time in your pregnancy that your due date may shift slightly, as measurements of fetal age are more reliable in the first trimester than at any other time.
A second ultrasound can take place between eleven and fourteen weeks, as part of the first-trimester combined screening. Also known as the nuchal translucency screening, it combines measurements of the fluid at the base of the fetus’s neck with results from a blood test to estimate the likelihood of genetic conditions like Down syndrome. The fluid in the nuchal fold is visible only during this period, while the tissue is still translucent.
The anatomy scan in the second trimester happens between eighteen and twenty weeks, and is your first real peek at your baby. During the thirty-to-forty-five-minute session, your baby’s head and trunk will be measured, and the weight will be estimated. The scan also checks amniotic fluid levels and the state and location of the placenta, and the baby’s kidneys, bladder, stomach, brain, spine, and sex organs. If you don’t want to know the gender, tell your sonographer before they start. It’s easy to see the presence (or absence) of a penis at this point.
Ultrasounds are usually only used later in pregnancy to monitor higher-risk women, so if yours is progressing without any issues, expect the anatomy scan to be your last. If you were hoping to get a preview of your baby’s size and weight, measurements taken in the third trimester are not very accurate, and can be off by as many as one or two pounds. For that reason, it is not used to refine your due date late in the game.
Your baby’s presence isn’t confined to your uterus. Just as the later explosion of toys in your house will register your child’s existence, their residency in your body is evident everywhere, by way of your bloodstream. Fetal placental fragments are detectable in your blood as early as ten weeks, and are the basis for noninvasive prenatal screening (NIPS, or NIPT). It is the most recent noninvasive testing option, and is often done in combination with the first-trimester combined test.3
Fetal placental fragments, which match the baby’s DNA, are sampled and analyzed to screen for chromosomal abnormalities. The test looks for a high number of certain DNA, as increased amounts may mean there are extra copies of those chromosomes.
How is it done?
Blood draw
When is it done?
Ten weeks, with results in seven to fourteen days
What does it test?
The majority of tests screen only for three main chromosomal conditions—trisomy 13, trisomy 18, and trisomy 21 (Down syndrome)—and sex chromosome abnormalities. NIPT also reveals the baby’s gender. Other genetic markers are still being evaluated for accuracy, so you probably will not see them in your results.
Who should get it?
Anyone can get this test, and it is increasingly offered regardless of your risk factors. It is encouraged for women who have a high-risk pregnancy, are over thirty-five, or have had a previous pregnancy with a chromosomal abnormality.
Advantages
It’s a noninvasive blood test, so there is no risk of miscarriage or complication. If the results come back clean, you likely will not need to move on to diagnostic testing. You can also elect to find out the gender months before the twenty-week anatomy scan.
Disadvantages
Screening tests are not diagnostic, meaning they cannot tell you with 100 percent certainty if your baby is going to be affected by any of these conditions. It assigns odds based on the presence or absence of extra chromosomal matter. If the screening is positive, your doctor will suggest a CVS or amnio to confirm. There can be false positives, especially in low-risk pregnancies. If you are looking for the most data possible, CVS and amnio can diagnose hundreds of conditions; NIPT screens for only four.
The quad screen provides your baby’s risk profile for certain genetic disorders and birth defects like Down syndrome and spina bifida (failure of the neural tube along the spine to close fully). If you’ve already cleared a first-trimester screening, it may not be offered. But in some pregnancies, findings from multiple screens are combined to improve the detection rate of some conditions.
How is it done?
Blood draw
When is it done?
Fifteen to twenty-two weeks
What does it test?
Four different markers in the pregnant woman’s blood: alpha-fetoprotein (AFP), estriol, inhibin A, and HCG
Who should get it?
Women with positive first-trimester screening, or NIPT results, or anyone who started prenatal care late
Advantages
The quad screen is noninvasive, and a negative result decreases the likelihood you will need diagnostic tests like amnio or CVS.
Disadvantages
The quad screen does have false positives and negatives and, like all screenings, gives you the chance of a condition, not a guarantee. If you have a positive screen, you’ll speak to a genetic counselor who will advise which diagnostic test is appropriate to provide a definite answer.
Chorionic villi are tiny hairlike projections found in the placenta that route nutrients, oxygen, and antibodies from you to your baby. They also hold fetal cells that contain your baby’s chromosomes and DNA.
The procedure removes these fetal cells from the placenta, where it attaches to the uterine wall. CVS is a conclusive diagnostic test, and can be done as early as ten weeks. It can confirm positive NIPT or NT screening results and check for inherited disorders, and serves as an earlier alternative to amniocentesis.4
How is it done?
CVS can be performed two ways—transabdominally with a needle inserted through the abdomen, or transcervically, using a small tube inserted through the cervix. Using ultrasound guidance, a sample of chorionic villi are suctioned or drawn from the placenta. The procedure can be uncomfortable, and some women experience cramping for several days afterward.
When is it done?
It’s the earliest available diagnostic test, done between ten and thirteen weeks. Results can come back in a few days, or weeks, depending on how many tests are run.
What does it test?
Hundreds of different genetic and chromosomal conditions. It also reveals the gender.
Who should get it?
CVS is offered only if there is an increased risk of genetic or chromosomal conditions, mostly due to a positive NIPT screening or a family or medical history.
Advantages
CVS is done earlier in pregnancy than amniocentesis and results come back quickly.
Disadvantages
CVS carries a less than 1 percent chance of miscarriage, and transcervical CVS can cause vaginal bleeding. Rates of miscarriage between transcervical and transabdominal procedures are the same. Sometimes the sample cells are not suitable for testing, so the procedure may need to be repeated. Unlike amniocentesis, CVS cannot detect any neural tube or anatomical defects.
German doctors first pioneered the technique behind amniocentesis in the 1880s to relieve excess amniotic pressure on a growing fetus.5 The amnio hit the medical mainstream in the 1950s, and is the most well known of the prenatal diagnostic tests. It can diagnose everything from genetic abnormalities and fetal lung maturity to infection through a sample of amniotic fluid. Amniotic fluid’s main job is to cushion and protect the baby in the womb, and to help regulate temperature. But it also contains fetal cells and proteins, which is the basis for the amniocentesis. It was used more frequently when there were fewer testing options, and due to the risks involved, should be used only if there are medical indications.
How is it done?
Using ultrasound guidance, your doctor will insert a thin needle into the amniotic sac away from the baby. A small sample of amniotic fluid is withdrawn, then sent to a lab and examined for genetic abnormalities. There can be stinging and cramping during the procedure, and it can cause discomfort afterward, so you’ll need to relax for the rest of the day.
When is it done?
Typically fifteen to twenty weeks into a pregnancy with results back in two weeks.
What does it test?
Many different birth defects and genetic conditions, from cystic fibrosis and Tay-Sachs to neural tube defects like anencephaly, which CVS cannot detect.6
Who should get it?
Women with abnormal ultrasounds, genetic screenings, or lab results, previous pregnancies or children with birth defects, a high-risk pregnancy, an infection like toxoplasmosis, or a family history of genetic or birth defects. It is also done for paternity testing.
Advantages
Amniocentesis is over 99 percent accurate in detecting genetic disorders and 90 percent accurate for neural tube defects.
Disadvantages
Similar to CVS, there is a less than 1 percent chance of miscarriage, and rare complications like preterm labor, leaking amniotic fluid, needle injury, and infection. Sometimes the test has to be repeated if the sample cannot be accurately tested. And though it is highly accurate, amnio cannot detect every single possible condition, or the severity, so there is still a chance that even with a normal result your baby will be born with a defect the test didn’t find.
These tests don’t come until later in your pregnancy, but in the spirit of getting the less fun stuff out of the way, and giving you an easy way to reference them later, we’ll cover them all in one spot.
Named for the rhesus monkey, which also carries the gene, Rh factor is a type of protein found on the surface of red blood cells. If you have the protein, you are Rh positive. Don’t have it? You are Rh negative. Eighty-five percent of people are Rh positive, and the only way your baby can be negative is for each parent to have at least one negative factor.
An incompatibility isn’t a problem for you. But it is for your baby, as your immune system will perceive the baby to be a foreign object and attack. Left unaddressed, the incompatibility can cause hemolytic anemia, which causes your baby’s red blood cells to be destroyed faster than they can be replaced. It can also lead to jaundice and to liver and heart failure.7
This screen is usually part of the blood draw at your first prenatal visit, so the incompatibility is easy to detect and treat. If you are found to be Rh negative, you’ll be given Rh immunoglobulin at twenty-eight weeks, and within seventy-two hours of birth.
File this one under gross unless you love really sweet beverages. The second-trimester glucose screening happens between twenty-four and twenty-eight weeks and checks to see if you have developed gestational diabetes. It can be done in the first trimester if you have a history of diabetes or other risk factors. The format: a blood test before and after you chug a small container of poorly flavored, very sugary water. Your blood glucose will be measured before and after the sugar bomb hits, and if the level is high, you’ll move on to a three-hour glucose tolerance test. This test is similar, but requires an overnight fast. Your blood sugar is measured before you drink the same unsavory drink, and then again once an hour for three hours. If your readings are still high, you will be diagnosed with gestational diabetes.
Between 2 and 10 percent of pregnancies are affected by gestational diabetes.8 With this diagnosis, you will be prescribed insulin or metformin, a blood sugar monitor to check your levels every few hours, a healthy diet, and regular exercise. Keeping gestational diabetes under control is important, since the condition increases your odds of having a larger-than-average baby, C-section, stillbirth, or preterm birth. And hey, learning things like the difference between good carbs and bad carbs is useful long after pregnancy is over.
Gestational diabetes typically goes away after birth, but 50 percent of those affected develop type 2 diabetes later. For that reason, your levels will be checked postdelivery, then monitored every three years.
Yes, we’re really jumping ahead a bit with this one, but hang tight. Also, get excited, as it’s the last mention of tests for a while.
Done during the third trimester, between thirty-six and thirty-eight weeks, the group B strep test is a simple swab test of the vagina and perineum. GBS is a normal bacteria in the vagina (about one in four women carry it), but it can be passed to your baby on its way out during birth.9 If that happens, it can cause severe lung, brain, and blood infections. Left untreated, there’s a one in two hundred chance of infection, and a 5 percent chance of infant death. If you are GBS positive and have a vaginal delivery, you’ll be given IV antibiotics. C-section moms do not need antibiotics unless the amniotic sac has ruptured.
Prenatal testing was my least favorite part of pregnancy. It is nearly impossible not to imagine all the things that can go wrong, even if there is no reason to suspect anything actually is. And if something goes wrong once, it’s even harder.
Two weeks after my miscarriage, the nausea and fatigue returned with a vengeance. Inexplicably, I was pregnant again. We weren’t trying, but we weren’t careful either. File under “things we wish we’d known”: You are especially fertile right after a miscarriage.
This pregnancy felt the same as the first, but with one big difference. I tried but just couldn’t feel excited about it. Every trip to the bathroom was stressful—I kept looking for signs it was going to go wrong again. I also couldn’t shake the feeling that something wasn’t right.
The first hint that my sinking feeling had merit came during our first prenatal appointment. The fetal measurements were already over a week behind. The doctor cautioned that we shouldn’t read too much into it, as it’s tough to get accurate dating so early. I still spent most of the day afterward googling what it could mean.
We planned to do the NIPT at ten weeks, both because of my dreaded advanced maternal age status, and since a clear screen reduces the need for invasive diagnostic tests.
When the genetic counselor called to say the NIPT was positive for trisomy 18, we had no idea what it was. A quick search revealed that it was not news we wanted. Also known as Edwards syndrome, trisomy 18 is a fatal developmental condition that often ends in stillbirth.10
We were devastated.
Our next step was to confirm the screening result through a CVS test. Test day was one of the worst days of our lives, especially because we were surrounded by happy pregnant bumps and new babies in the waiting room. The CVS was unpleasant (felt like being pinched from the inside), but the silent, joyless ultrasound was worse. I couldn’t stop sobbing.
Our fears were confirmed a very long week later when the CVS results came back. It was indeed trisomy 18, and combined with the ultrasound findings our best-case scenario was stillbirth within just weeks or months. I talked to our genetic counselor several times just to make sure I understood every possible outcome, called a genetics expert friend to vet the efficacy of the tests, and contacted a neonatologist so that we could fully understand the condition. They all confirmed that we should take the results seriously, and that there was no possibility of a happy ending. It was over.
Terminating a wanted pregnancy, even under those circumstances, was the hardest choice I’ve ever had to make.
The day of the procedure, it took a full morning of waiting for my cervix to ripen; the actual dilation and curettage (D&C) procedure took only thirty minutes. The dilation was uncomfortable, but other than feeling groggy and emotionally drained, I otherwise experienced very little pain.
A few close friends stopped by that evening with dinner, hugs, and distraction. If there was a silver lining, it was that when we did eventually have a baby, he or she would come into a world full of so much love and support.
The morning after the D&C, every pregnancy symptom was gone. And after just a day of light spotting, it was as if the whole thing had never happened.
The wait time to conceive again is at least two months so hormones can disappear and the cervix can heal. As we learned before, the cycle right after a pregnancy ends can be very fertile, so this time we took precautions.
After our two-month hiatus, I was pregnant. Again. The first cycle we tried. Nick and I agreed not to obsess about what could go wrong and just let it be. We knew we were lucky to get pregnant so easily; now we just had to wait.
We cleared the NIPT screening and, since everything was normal, did not opt into any diagnostic testing. While I definitely had (many) moments of anxiety, we decided to follow the process and not seek out more information than we needed.
It wasn’t easy getting through the first trimester. But, fortunately, this pregnancy was much easier from the start. Maybe because I had more perspective. Perhaps because I was full of so much love for the people who surrounded us while we struggled. Certainly because I had no morning sickness. Definitely because I stopped white-knuckling and trying to assert control over the process.
Even with many of my friends in the health community, I could find no one else who had actually been through anything similar. It was this experience more than any other that inspired me to write this book.