You’re doing great, mama! You’ve made it to the second trimester, and this is where the fun starts. Many of us wave goodbye to the nausea and fatigue around this time — even though we thought they’d never leave. And as that cute baby bump gets larger, you can finally parade the maternity clothing you’ve stashed in the closet!
This is also a time when you’ll hear about the quad screen prenatal test at your healthcare provider’s office. So what is it, and should you get it done? Let’s demystify it a bit.
The quad screen — also called the maternal serum screen — is a prenatal screening test that analyzes four substances in your blood. (Thank Latin for that — quad means four.) It’s usually carried out between your 15th and 22nd week of pregnancy.
The quad screen can tell you if your baby has an increased chance of:
- Down syndrome
- trisomy 18 (Edwards Syndrome)
- neural tube defects
- abdominal wall defects
It does so in part by measuring these four substances:
- alpha-fetoprotein (AFP), a protein produced by your baby’s liver
- human chorionic gonadotropin (hCG), a hormone produced by your placenta
- estriol, a hormone made by your placenta and the baby’s liver
- inhibin A, a third hormone produced by your placenta
Yup, pregnancy is a heavy hormone-production 9 months. Now you can stop wondering why you’ve been feeling so tired!
The quad screen is a simple blood test — you’ve probably had a needle inserted into a vein in your arm before, and it’s no different. Since it’s your blood that’s being tested, there’s no risk to your baby. The blood is sent to a lab for analysis, and within a few days you’ll get the results. Easy peasy.
This is an optional test, which means you don’t have to do it. But many doctors recommend it for all pregnant women. Here’s what might make you opt in:
- You’re 35 or older. Since the test is noninvasive, if you’re worried about your baby’s health only because of your age, this test is a good option.
- Your family has a history of developmental irregularities at birth (e.g., spina bifida, cleft palate).
- You’ve already had a child with developmental irregularities at birth.
- You have type 1 diabetes.
Keep in mind that the quad screen doesn’t just look at the results of your blood test. It adds in different factors — such as your age, ethnicity, and weight — and then estimates the chances that your baby may have an abnormality.
The screen doesn’t tell you that there’s definitely a problem; if abnormal, it tells you that you should have further testing.
By now, you’ve realized that each week of pregnancy is different than the week before. (The 10 jars of pickles you asked for last week are now probably being used as door stoppers.) That means that the levels of AFP, hCG, estriol, and inhibin A in your blood are also changing week by week.
That’s why it’s important to make sure you’ve told your OB how far along you are in your pregnancy. By using
What the results mean
Want to take a deep breath before we look at what the results could mean? You’re right, thinking about these conditions can be downright scary. However, even if your quad screen is positive (meaning that there are higher chances that your baby could have one of these conditions), it doesn’t necessarily mean that your baby will be affected. It just means that the chances are higher.
If you’re thinking, “Huh?” here’s an example: About 4 percent of quad screens will return positive for an increased risk of Down syndrome, but only about .1 to .2 percent of those babies will have Down syndrome. Breathe out now.
Let’s skirt round the exact numbers and get to the nitty gritty according to the Cleveland Clinic:
- Higher than normal AFP levels could mean that your baby has an open neural tube defect such as spina bifida or anencephaly. On the other hand, they could also mean that he’s older than you thought or that — guess what — you’re expecting twins.
- Lower than normal AFP, hCG, and inhibin A levels could mean that you have higher chances of having a baby with Down syndrome or trisomy 18.
- Lower than normal levels of estriol may also mean that you have higher chances of having a baby with Down syndrome or trisomy 18.
More on the conditions
- Down syndrome is a genetic condition that comes from extra genetic material (the 21st chromosome). Approximately
1 in 700babies is born with Down syndrome.
- Trisomy 18 is a genetic condition that comes from extra chromosome number 18. Most trisomy 18 pregnancies result in miscarriages or stillbirth; babies who are born, live for only a few years. About 1 in 5,000 babies is born with this condition.
- Neural tube defects include conditions like spina bifida or anencephaly. Spina bifida is when the brain, spinal cord, or the spinal cord’s protective covering doesn’t develop properly. Anencephaly means that the baby’s brain doesn’t form completely. Neural tube defects occur in 1 or 2 out of every 1,000 births.
- The test can detect approximately 75 percent of Down syndrome cases in women under age 35 and 85 to 90 percent of Down syndrome cases in women age 35 years and older. Remember, though, that most people who are told they have an increased risk of having a Down syndrome baby don’t end up having a baby with Down syndrome.
- It can also detect approximately 75 percent of open neural tube defects.
- If the quad screen test is negative, there’s still a possibility that your baby could be born with one of these conditions.
What happens if you have a positive quad screen test? First, remember that many women who show positive test results go on to have babies that are just fine.
The next step is a consultation with a genetic counselor, and together you’ll decide whether further testing is right for you. Sometimes this means another quad screen test and a high definition (targeted) ultrasound. And then, if the results are still positive, you may want to do the following tests:
- Prenatal cell-free DNA screening. This blood test examines cell-free DNA coming from your placenta and your baby and found in your bloodstream.
- Chorionic villus sampling (CVS). A sample of tissue from the placenta is removed for testing.
- Amniocentesis. A sample of amniotic fluid is drawn for testing.
The downside here is that both CVS and amniocentesis pose a slight threat for miscarriage.
If you don’t want to know before birth that your baby may have a chance of having Down syndrome, trisomy 18, a neural tube defect, or an abdominal wall defect, the quad screen test isn’t for you.
On the other hand, you may want to know what the chances are so that you can begin to plan for a baby with special needs, find out about support groups and resources, and start to think about how your life is going to be affected.
And your healthcare provider is there to help. If you’re wondering about the quad screen and how to interpret results, ask your doctor or midwife — they can give you the most accurate picture of what to expect.