Different tests can screen for different conditions at different stages in your pregnancy. The earliest test is available at 10 weeks and others at about 16 and 20 weeks.
At 10 weeks or after
There’s a non-invasive screening test to look for genetic abnormalities such as Trisomy 13, 18, and 21 as well as conditions including Turner syndrome and Klinefelter syndrome.
These involve the baby having an extra or missing chromosome. Trisomy 21 is the most common – what we typically think of as Down syndrome. The others happen less frequently, and babies born with these conditions sometimes don’t live longer than a year.
Not all clinics offer this test, and if you’re at a low risk level, your insurance usually doesn’t cover it. The biggest risk factor for having a baby with Down syndrome is just maternal age. It’s not about family history or anything. So this is not necessarily a test that most women will get.
Here’s how it works: We take some blood from you. Because the baby’s cells float with the mother’s cells in the blood, we’re able to analyze the DNA and see if your baby might have one of those conditions.
If any are detected, we set you up with a genetic counselor to discuss your options for further tests to confirm the results, because none of these early screenings are 100 percent accurate. You could get a false positive when your baby doesn’t have the condition, or a false negative when your baby actually has the condition.
At 16 weeks
A less accurate but slightly broader prenatal screening test is the “multiple marker” – either a “triple screen” or “quad screen,” depending on what’s measured in your blood. Combined with an ultrasound, this blood test is used to look for the possibility that your baby has Down syndrome or a neural tube defect.
A neural tube defect is when something’s not quite right with the spine. The most common one is spina bifida, when the skin around the baby’s spine doesn’t close completely and there’s a hole going into the spine.
The risk factor for having something like this would be family history or not having an adequate diet, but your risk level is still pretty low.
This test can be done between 15 and 20 weeks, but 16 to 18 weeks is considered the best window. Not all women choose to get this test, but some want it for peace of mind. Most prenatal-care packages in insurance plans cover it.
You could skip this test and wait for the 20-week anatomy ultrasound that most women get. If a baby’s genetic problems are severe enough, we may see it in the ultrasound – but not always.
At 20 weeks
The goal of the anatomy ultrasound is to take a look at the kidneys, the heart, the brain, and everything else to make sure the baby is healthy.
We call it the 20-week ultrasound because it’s usually done between 18 and 22 weeks. It’s the time when the anatomy is developed enough to see things, but the baby isn’t so big that things are hidden.
Most clinics will require it, but there are some that don’t. This is another test that is standard for insurance to cover.
Many women want it, because it’s also when you can find out the sex of the baby. (Unless you’d like to wait and let nature surprise you!)
Fairview Center for Women – Edina
To learn more:
Make an appointment with a midwife or OB doctor
or book a tour at The Birthplace.