Patient FAQs
Frequently Asked Questions About
First Trimester Screening (FTS):
What is the first trimester screen?
What is Down syndrome and Trisomy 18?
How accurate is the first trimester screening?
When can the first trimester screening be performed?
What is involved in the first trimester screen?
Will the screening test tell me for certain if my baby has Down syndrome or Trisomy 18?
What if my screening test shows an increased risk?
What if my screening test does not show an increased risk?
Other than the first trimester screening, what other test should I have?
Who is a good candidate for the first trimester screening?
What if I will be 35 years or over at the time of delivery?
Can I still have the first trimester screen if I am carrying twins?
Frequently Asked Questions About
AFP/freeBeta Second Trimester Screening:
What is the second trimester AFP/freeBeta screen?
What are ONTD, Down syndrome and Trisomy 18?
How accurate is the second trimester AFP/freeBeta screen?
When can the second trimester AFP/free beta hCG screen be performed?
What is involved in the second trimester AFP/freeBeta screen?
Will the screening test tell me for certain if my baby has a birth defect?
What if my screening test shows an increased risk?
What if my screening test does not show an increased risk?
Who is a good candidate for the second trimester AFP/freeBeta screening?
What if I will be 35 years or over at the time of delivery?
What is the first trimester screen?
The first trimester screening is a combination of a maternal blood test and a special ultrasound which identifies fetuses at increased risk for certain conditions like Down syndrome and Trisomy 18. The blood test measures 2 proteins- free beta hCG and PAPP-A. The ultrasound measures fluid accumulation on the baby's neck, called nuchal translucency (NT). This test is safe for you and your baby.
What is Down syndrome and Trisomy 18?
Down syndrome and Trisomy 18 are both chromosomal disorders that result from having an extra chromosome in each cell. The extra chromosome causes birth defects and mental retardation.
How accurate is the first trimester screening?
The blood test alone (without the ultrasound NT measurement) identifies 68% of Down syndrome and 90% of Trisomy 18 fetuses. The blood test and ultrasound when used in combination has a 91% detection rate for Down syndrome and 97% detection rate for Trisomy 18. The test can also pick up 40% of fetuses with heart defects and some other birth defects.
When can the first trimester screening be performed?
The blood test alone (without the ultrasound) can be performed between 9 weeks to 13 weeks 6 days. First trimester screening using maternal blood and ultrasound NT measurement is performed between 11-13 weeks 6 days (45-84mm CRL)..
What is involved in the first trimester screen?
The first trimester screen is a combination of a blood and an ultrasound test. A small amount of maternal blood is drawn either in a tube or by finger stick. A few drops of blood are then dried on special paper. The ultrasound is performed to measure the nuchal translucency (fluid accumulation at the back of the fetal neck). The nuchal translucency should be measured by certified health care providers. The values obtained are analyzed by GeneCare to provide risk estimates for Down syndrome and Trisomy 18.
Will the screening test tell me for certain if my baby has Down syndrome or Trisomy 18?
A screening test will only provide a risk estimate i.e. it will tell you your risk for Down syndrome or Trisomy 18 is increased or within normal range. A screening test cannot diagnose or rule out any specific condition.
What if my screening test shows an increased risk?
An increased risk for Down syndrome or Trisomy 18 does not mean a chromosome abnormality has been diagnosed. It only means your risk to have a baby with Down syndrome or Trisomy 18 is increased. Your health care provider and/or genetic counselor will discuss additional testing options like a CVS or an amniocentesis which have 99.9% detection rates for chromosome abnormalities.
What if my screening test does not show an increased risk?
This means that your risk for Down syndrome and Trisomy 18 has been reduced. Screening tests cannot rule out Down syndrome or Trisomy 18. Down syndrome and Trisomy 18 make up only about half of all chromosome abnormalities. First trimester screening cannot estimate a risk for the other half of chromosome abnormalities and will not detect many of them.
Other than the first trimester screening, what other test should I have?
The first trimester screening cannot screen for open skull or open spine defects. These birth defects usually occur without a family history. A maternal blood test at 13-22 weeks to measure the alpha-fetoprotein (AFP) level is recommended. This blood test screens for 98% of open spine and skull defects at 13 weeks 4 days to 22 weeks 3 days. Your health care provider may also discuss another ultrasound in the second trimester.
Who is a good candidate for the first trimester screening?
Because 80% of Down syndrome and Trisomy 18 babies are born to women less than 35 years at the time of delivery, the first trimester screening is offered to women who will be less than 35 years at delivery and have no family history of a chromosome abnormality and neural tube defects like spina bifida.
What if I will be 35 years or over at the time of delivery?
The American College of Obstetricians and Gynecologists (1994) and the American College of Medical Genetics (1993) recommend all women who will be 35 or older at delivery or have a positive family history routinely be offered amniocentesis or CVS for prenatal chromosomal testing to diagnose 99.9% of all chromosomal abnormalities. Screening is not a substitute for amniocentesis, because:
- It does not give a diagnosis
- It only estimates a risk for only 2 chromosomal abnormalities
- It will miss many of the hundreds of other types of chromosomal abnormalities
- It may falsely reassure patients who after screening still have an increased chromosomal abnormality risk due to age. If you have decided to have an amniocentesis, this test is not necessary.
If you are over 34 and decline an amniocentesis or CVS, EarlyScreen can assess your risks for Down syndrome and Trisomy 18, but not other chromosomal abnormailities.
Can I still have the first trimester screen if I am carrying twins?
First trimester screening can be performed on women carrying twins with a Down syndrome detection rate of 80%. Twin screening using only the nuchal translucency measurement is equally sensitive in both singleton and multiple pregnancies. Twin screening with freeBeta/PAPP-A reduces the SPR from 12.4% to 7.2%.
What is the second trimester AFP/freeBeta screen?
The second trimester AFP/free beta hCG screen is a maternal blood test performed between 13 weeks 4 days and 22 weeks 3 days which identifies fetuses at increased risk for conditions like open neural tube defects (ONTD), Down syndrome and Trisomy 18. The blood test measures the level of 2 proteins- free beta hCG and AFP in maternal blood. This test is safe for you and your baby.
What are ONTD, Down syndrome and Trisomy 18?
ONTD or open neural tube defects are the most common group of birth defects. They are also referred to as open spine or open skull. This group of birth defects usually occur without a family history and is not associated with maternal age. Down syndrome and Trisomy 18 are both chromosomal disorders that result from having an extra chromosome in each cell. The extra chromosome causes birth defects and mental retardation.
How accurate is the second trimester AFP/freeBeta screen?
The second trimester AFP/free beta hCG screen has an 80% detection rate for Down syndrome, a 70% detection rate for Trisomy 18 and a 98%detection rate for ONTD.
When can the second trimester AFP/free beta hCG screen be performed?
The blood test can be performed as early as 13 weeks 4 days and up to 22 weeks 3 days.
What is involved in the second trimester AFP/freeBeta screen?
A small amount of maternal blood is drawn either in a tube or via a finger stick. A few drops of blood are then dried on a special paper. The blood is then analyzed by GeneCare to provide risk estimates for Down syndrome and Trisomy 18.
Will the screening test tell me for certain if my baby has a birth defect?
NO. A screening test will only provide a risk estimate i.e. it will tell you your risk for Down syndrome, Trisomy 18 or ONTD is increased or within the normal range. A screening test cannot diagnose or rule out any specific condition.
What if my screening test shows an increased risk?
An increased risk for ONTD, Down syndrome or Trisomy 18 does not mean an abnormality has been diagnosed. It only means your risk to have a baby with the condition is increased. Your health care provider and/or genetic counselor will discuss additional testing options like a CVS or an amniocentesis which have 99.9% detection rates for chromosome abnormalities.
What if my screening test does not show an increased risk?
This means that your risk for ONTD, Down syndrome and Trisomy 18 has been reduced. Screening tests cannot rule out an abnormality. Down syndrome and Trisomy 18 make up only about half of all chromosome abnormalities. Second trimester screening cannot estimate a risk for the other half of chromosome abnormalities and will not detect many of them.
Who is a good candidate for the second trimester AFP/freeBeta screening?
Because 80% of Down syndrome and Trisomy 18 babies are born to women less than 35 years at the time of delivery, the first trimester screening is offered to women who will be less than 35 years at delivery and have no family history of a chromosome abnormality and neural tube defects like spina bifida.
What if I will be 35 years or over at the time of delivery?
Women 35 years or over at the time of delivery are at a higher risk for chromosome abnormalities one of them being Down syndrome. Down syndrome only accounts for 40% of the total screening risk, first trimester screening cannot estimate a risk for the other half of chromosome abnormalities and will not detect many of them. The American College of Obstetricians and Gynecologists (1994) and the American College of Medical Genetics (1993) recommend all women who will be 35 years or older at the time of delivery or have a positive family history routinely be offered CVS or amniocentesis for prenatal chromosome testing. The CVS and amniocentesis can diagnose 99.9% of all chromosomal abnormalities. For women 35 yrs or over at the time of delivery, screening is not a substitute for a diagnostic test like CVS and amniocentesis because:
- Second trimester AFP/freeBeta screening only provides a risk estimate (a probability) for Down syndrome and Trisomy 18, it does not give a diagnosis.
- Second trimester AFP/freeBeta screening estimates a risk for only 2 chromosome disorders, Down syndrome and Trisomy 18, and will miss many of the hundreds of other types of chromosome abnormalities.
- A screen result that is within the normal range suggests a lower risk. Only a CVS or amniocentesis can determine with 99.9% accuracy if a fetus has a chromosome abnormality
- Screening may falsely reassure some patients who after screening have an increased chromosome abnormality risk due to age.
For all women 35 years or older at the time or delivery or those with a family history of chromosome abnormality, genetic counseling is recommended to discuss the availability, benefits and limitations of different testing options. GeneCare recognizes that some women 35years or older will elect to have blood screening and decline a diagnostic procedure. Keep in mind that the second trimester screen can only assess your risk for ONTD, Down syndrome and Trisomy 18, but not your risk for other chromosome abnormalities.