One of the very first tests that your doctor may offer you is a First Trimester Screening. Screening and diagnostic tests were typically recommended for women over the age of 35, but more and more doctors are offering these tests to women of all ages. The First Trimester Screen is a fairly new screening test; it is used primarily to detect Trisomy 18 and Trisomy 21 (Down Syndrome).
If you express interest in this screening, let you doctor know, as the testing needs to be completed between 11 and 14 weeks of pregnancy. Your physician will typically send you to a facility with trained doctors, geneticists, and ultrasound technicians that have the capability of completing this test. The test is noninvasive; it is a combination of blood work and ultrasound (sonogram).
What are they looking for in the blood work?
- Pregnancy-associated plasma protein A (PAPP-A)
- Free beta subunit of human chorionic gonadotropin (bHCG)
PAPP-A and hCG Test
Your blood will typically be taken with a finger prick and sent off to a lab. The blood is tested for PAPP-A and hCG. Potential chromosomal abnormalities exist where the PAPP-A levels are to be found considerably low and with hCG levels that are significantly high. The blood levels will be combined with the results from the ultrasound to give you a risk factor for possible chromosomal abnormalities.
Nuchal Translucency: What are they looking for in the ultrasound?
During the nuchal translucency test, an ultrasound will be done to check the clear space in the tissue at the back of the baby’s neck. Babies with abnormalities have a tendency to collect more fluid at the back of their neck during the first trimester, making the space larger than expected. The ultrasound technician must be skilled using advanced equipment to ensure that they are gathering appropriate measurements.
Your screening results
You can expect your screening results within about a week after you initial testing. Many things will be factored in for your screening results such as blood test results, ultra sound results and maternal age. Most likely you will be given a number that correlates to a risk factor (for example 1/250.) Remember a screening test will not give you a diagnosis, but instead may indicate the want or need for further testing. About 85% of abnormalities will be able to be identified on a first trimester screening test. Keep in mind there is about a 5% false-positive rate with this screening test. If further testing is desired, you may choose more screening tests in the second trimester or diagnostic tests such as CVS or amniocentesis.
Screening tests can help assess the risk of a birth defect. It is more and more common to see testing offered to all pregnant women. Other tests may be suggested based on your history, age and/or risk factors. Discuss with your doctor about which screening test is right for you.