1st Trimester Down Syndrome Screening
Early Screen First Trimester; Prenatal Screening and Ultrasound Exam (aka Nuchal Fold Test, Ultrascreen)
What is Early Screen®?
Early Screen is a blood test combined with an 11-13 week ultrasound exam that tells you if you have an increased chance of having a baby with Down syndrome, Trisomy-18 or ?13. These disorders result from an extra chromosome in each cell. The extra chromosome causes birth defects and mental retardation. The risk of having a baby with an extra chromosome disorder increases with the mother’s age, but can occur at any age.
What are Down syndrome, Trisomy 18 and Trisomy 13?
Down syndrome occurs when the baby has an extra copy of chromosome 21. Babies with Down syndrome have mental retardation and usually have physical anomalies, like heart defects.
Trisomy 18 is caused by an extra chromosome 18 and trisomy 13 by an extra chromosome 13. Both these disorders cause profound mental retardation and multiple birth defects. While trisomy 18 and trisomy 13 are more severe than Down syndrome, they are less common.
How is Early Screen Performed?
Blood is taken from your arm or through a finger stick to measure the levels of two proteins (freeBeta and PAPP-A) in your blood. These two proteins are normally found in your blood. Your ultrasound exam will measure your baby?s nuchal translucency (NT), a fluid filled space at the back of the baby?s neck and may examine the nasal bone.
What If My Screening Test Shows My Risk Is Increased?
It does not mean a chromosomal abnormality has been diagnosed. It means your chance of having a baby with a chromosome abnormality is high enough to offer further testing. You will be offered genetic counseling, and a safe diagnostic amniocentesis or CVS test. CVS is a test in which a small amount of placental tissue is collected. Amniocentesis is a test in which a small amount of fluid from around the baby is collected for chromosome analysis.
What If My Early Screen Test Does Not Show An increased Risk?
This reduces your risk but does not rule out Down syndrome, trisomy-18 or ?13. They makeup only about half of all chromosomal abnormalities. Early Screen will detect some but not all of the other half of chromosomal abnormalities.
Who Should Be Offered Early Screen?
Early Screen should be offered to all women who will be less than 35 at delivery and have no family history of chromosomal abnormalities.
All women who will be 35 or older at delivery or have a positive family history are routinely offered Amniocentesis or Chorionic Villus Sampling (CVS) for prenatal chromosomal testing to diagnose 99.9% of all chromosomal abnormalities.
Early Screen is a screening test which does not diagnose or rule out any specific condition.
Women who decline amniocentesis may have Early Screen, but need to know Early Screen is not a substitute for Amniocentesis, because:
- It does not give a diagnosis.
- It estimates a risk for only 3 chromosomal abnormalities.
- It will miss some chromosomal abnormalities which would be diagnosed by amniocentesis or CVS.
- It may falsely reassure some patients who after screening still have an increased chromosomal abnormality risk due to age or family history.
What Other Tests Should I Have?
An Alpha-Fetoprotein (AFP) blood test or an ultrasound exam to screen for 98% of open spine.
Should I Have An Additional Second Trimester Screening for Down Syndrome and Trisomy 18?
NO. Repeating a second chromosomal screen is not recommended as standard of care. Why?
Because Early Screen is more accurate and less likely to give a false risk result than a repeat test. Any follow-up chromosomal screen test is more likely to give a false risk result and is unlikely to improve detection.
Should I Have Screening If I Plan To Continue The Pregnancy Under Any Circumstance?
You are being offered Early Screen because your physician feels it may provide information which will be helpful to you and your husband. It is entirely up to the patient if they want to pursue testing, it is not mandatory, as is any medical test, the patient has ultimate authority if they want to get a test or decline one.