Prenatal Testing
There have been amazing advances in the accuracy and safety of testing available, but important to remember there are still false positives, false negatives, and no way to test for all possible conditions (e.g. no way to test for Autism).
Non-Invasive Prenatal Testing (NIPT)
Why?
This test looks at the 3 biggest “trisomies” - disorders caused by having an extra, third chromosome, the most common being Down’s Syndrome - along with some other disorders affecting the sex chromosomes
It does not test for neural tube defects like spina bifida; this can be done in a second trimester blood test called a quad screen or “alpha-fetoprotein” (AFP) test
It can also tell you the sex of your baby way earlier than you would learn by ultrasound (if you don’t want to know, you can just not check that box in the order form)
The test uses your blood, which contains free-floating DNA cells both from you and from your fetal cells from the placenta and counts the number of chromones of different types to determine if there are any extras or missing ones
It is considered a screening test, rather than a diagnostic test - it can only tell you if there is higher risk, rather than whether your baby actually has one of these disorders. If you were to receive a result of higher risk, next step would likely be CVS or Amniocentesis
When?
10 weeks or later
How?
Ask your OB if they have a kit or can order you one; you’ll then take it to wherever you get lab work done to have your blood drawn
Natera - Panorama is the most accurate and comprehensive, and is in-network for most of the big insurance plans (though you may still have to pay some amount out-of-pocket). I’d recommend calling your insurance beforehand to determine the cost - it shouldn’t be more than $200.
Results come back within 1-2 weeks
Nuchal Translucency Scan
Why?
This is a special ultrasound, not a genetic test, but combined with the NIPT or other blood test results it can give you further information about risk of a trisomy disorder, the most common being Down’s Syndrome.
Looks at fluid levels behind baby’s neck; all babies have some, but babies with these conditions tend to have excess amounts
Like the NIPT test, this is a screening test, not a diagnostic test, meaning it can indicate whether your baby might be at higher risk but can’t say for certain if they have the disorder - CVS or Amniocentesis would be required for that. There is a fairly high false positive rate.
When?
Between 11 and 13 weeks
How?
Your OB will either perform or give you the order form for the ultrasound; as a bonus, you’ll get a nice peek at your baby!
Unlike your earlier “dating” ultrasound that was likely vaginal, this one can be done over your abdomen so isn’t invasive at all (if you didn’t get a separate “viability and dating” ultrasound, they will estimate your due date with this one)
This is covered by insurance
Chorionic villus sampling (CVS)
Why?
This isn’t a routine test, but is given if you or your partner have a family history of a genetic disorder, are carriers of a disorder, came up as high risk on NIPT or other tests, or are of “advanced maternal age” (over 35) and want to be extra safe
This is a diagnostic test that takes a sample of cells from the placenta, which have the same genes as the fetus, so the accuracy is pretty much 100%
It can test for Down’s Syndrome, Cystic Fibrosis, Sickle Cell and Tay-Sachs, plus other rarer conditions
Unlike Amniocentesis or AFP blood testing, it cannot test for spina bifida
It also can’t tell you about defects like cleft palate or heart defects, which the anatomy scan later in pregnancy can look for
When?
Between 10 and 14 weeks, so meaningfully earlier than Amniocentesis which can’t be done until 16 weeks; this could allow you greater decision making time if you were to receive a diagnosis
How?
There are two methods, which are equally safe
“Transabdominal”: a needle is inserted into your abdomen after local anesthesia; Doctor is guided by an ultrasound to the placenta and collects cells (very similar to amniocentesis)
“Transcervical”: Just like a pap smear, a device is used to widen your vaginal walls and then a tube is inserted into your cervix. Again, doctor is guided by a ultrasound to move the tube towards the placenta and collect some cells.
Recent research suggests risk of miscarriage for both CVS and amniocentesis is actually much lower than has traditionally been cited; basically negligible increased risk compared to controls (especially if you are having the procedure done by an experienced doctor)
Amniocentesis
Why?
Like CVS, this isn’t a routine test, but is given if you or your partner have a family history of a genetic disorder, are carriers of a disorder, came up as high risk on NIPT or other tests, or are of “advanced maternal age” (over 35) and want to be extra safe
This is a diagnostic test that looks at amniotic fluid, which contains fetal DNA, so the accuracy is pretty much 100%
Can test for Down’s Syndrome, Cystic Fibrosis, Sickle Cell, Tay-Sachs, and spina bifida (which CVS doesn’t), plus other rarer conditions
When?
After 16 weeks
Even if you know you will carry through with the pregnancy regardless of the results, it can still be helpful to be equipped with diagnosis in order to plan and prepare for supporting your child’s needs
How?
Using an abdominal ultrasound as a guide, a long thin needle is inserted into your abdomen and into the amniotic sac to draw out some amniotic fluid
Recent research suggests that the risk of miscarriage for both CVS and amniocentesis is actually much lower than has traditionally been cited; basically negligible increased risk compared to controls (especially if you are having the procedure done by an experienced doctor)
Quad Screen/Alpha-fetoprotein (AFP)
Why?
The Quad screen is a blood test that looks at levels of four substances in your blood that can indicate higher risk of the three big trisomies (Down’s Syndrome being the most common) and also neural tube defects (like Spina Bifida)
This can be done as a cheaper alternative to the NIPT, but it isn’t as accurate; if you can afford NIPT, I’d opt for that
However, NIPT doesn’t test for neural tube defects, so in addition to NIPT, ask your OB about doing the AFP component of the screen to test for these issues
This is sometimes part of a “integrated” or “sequential” screening, that combines the Nuchal scan and a first trimester blood test (for people who aren’t doing the NIPT)
In CA, all women are offered this “integrated screening”
Again, this is a screening test, not a diagnostic test, meaning it can indicate whether your baby might be at higher risk but can’t say for certain if they have the disorder - CVS or Amniocentesis would be required for that
When?
Between 15 and 20 weeks
How?
Simple blood draw, results in 1-2 weeks
