First Trimester Screening
First trimester screening is a prenatal test that allows us to get information on the baby’s risk of having some congenital anomalies causing Down’s Syndrome also known as trisomy 21 or Edwards syndrome also known as trisomy 18.
First trimester screening involves combined Laboratory tests such as:
- Blood test: This lab test is taken to measure the levels of two pregnancy-specific substances present in the mother’s blood – Pregnancy-Associated Plasma Protein A and HCG (Human chorionic gonadotropin).
- Ultra Sound: The ultrasound is done to analyze the amount of the clear space in the tissue at the back of the neck also known as nuchal translucency.
The first trimester screening is done between 11 to 14 weeks. According to your age, the results of the blood test, and the ultrasound, your doctor will let you know, if there is a risk of carrying a baby with Down syndrome or trisomy 18. If the results show that the risk level is either moderate or high, then your doctor will recommend you to get some other tests to be more definitive and sure.
The doctor may also suggest a Quadruple screen which is done between 15- 20 weeks of pregnancy as it evaluates the risk of carrying a baby with Down syndrome, trisomy 18 as well as neural tube defects or Spinal Bifida. The doctor may suggest Quadruple screen along with first trimester screening which is also known as Integrated Screening which improves the detection rate of the Down syndrome.
First trimester screening is optional as the results indicate whether you have the risk of carrying a baby with Down syndrome or trisomy18. First trimester screening does not involve any risk to the pregnancy and does not increase the risk of miscarriage.
In case you receive a positive test result, your doctor can discuss further options with you and
that may include additional tests such as:
- Prenatal cell-free DNA screening: This lab test analysis’s fetal DNA in the bloodstream to find out whether your baby is at the risk of Down Syndrome. This screening is also done to check for other chromosome problems. The normal result of this test eliminates the need for more-invasive prenatal diagnostic.
- CVS (Chorionic villus sampling): This lab test is done to diagnose chromosomal conditions such as Down syndrome. It is done in the first trimester. During this lab test, a sample of tissue is removed for testing from a placenta. This Lab test carries a small risk of having a miscarriage.
- Amniocentesis: This laboratory test is done to diagnose both chromosomal conditions as well as neural tube defects such as spinal Bifida. This lab test is usually done during the second trimester and during this test, a sample of amniotic fluid is taken from the uterus. Like CVS, this test also carries a small risk of having a miscarriage.
Your doctor will help you understand your test results and what the results may mean for your pregnancy. It is advisable to take first trimester screening to be sure whether your baby has any risk of serious health condition. Chromosomal abnormalities are associated with pregnancy in women that are aged 35 or older, but they can happen at any age. Babies with Down syndrome may be born to women under the age of 35 as well.