What is Sequential Screening?
Sequential Screening is a way of estimating the chance that a baby will be born with Down syndrome (T21), Trisomy 18, Trisomy 13, or a neural tube defect such as spina or anencephaly.
The test combines measurements from an ultrasound at 11-13 weeks, two blood tests, along with other details about you (such as age), to tell you more about your risk for a baby with the above conditions. Screening tests cannot diagnose – so if you have a high risk result you would need a follow up test (CVS, amnio) to do so, if that’s what you choose to do.
This test is elective.
How the test works:
Sequential Screening is a two-step process, but if you are at higher risk for Down syndrome or Trisomy 18, you will be usually be notified after the ultrasound and first blood test.
- Two blood tests measure proteins that are made by the developing baby and placenta. The first blood test is taken between the 11th and 13th week of your pregnancy. The second blood test is taken ideally between 16 and 18 weeks, although it can be done slightly later. Either blood test can show a high risk of a problem.
- An ultrasound is performed between the 10th and 13th week of pregnancy. First the baby’s length is measured to confirm that you are in the right time frame for the screening. They then measure the fluid-filled space at the back of the baby’s neck, which is called the nuchal translucency.
What if the test is positive?
If your test comes back positive, you are considered to be at high risk for the above disorders. A positive result does not mean that your baby has one of these problems – just that further workup is warranted, if you choose to do so.
Why did I choose to do this test?
- For me, it provided peace of mind. It was another chance to get a look at my developing little one and see that he/she is doing ok in there – what can I say, I’m ultrasound dependent…
- Another reason – if something was found on the test, it would give me the option to prepare for life with a special needs child. I would want to look into resources before the birth, so everything would be in place when the time came.
- More importantly – some problems can be prevented or even fixed if known early. For example, some neural tube defects can be fixed prenatally with surgery and some complications could be prevented if it was a C-section instead of a vaginal birth.
- Another reason – not for me, but every family needs to do what’s right for them – if the diagnostic tests with follow the sequential screen DO diagnose a problem, some may choose to abort. (Totally separate debate and not getting into that now.)
*Please note: I am not a medical doctor – this is what I know from my research and understanding and may not be 100% accurate or up to date.*