Overview
Prenatal screening in the first trimester is a test that provides early information about a baby’s risk for certain chromosomal disorders, including Down syndrome (trisomy 21, and different sequences on chromosome 18 (trisomy 18).
The first-trimester screening (also known as the first trimester combined testing) has two steps.
- Two pregnancy-specific substances are measured in blood: pregnancy-associated plasma protein A (PAPPA) and human Chorionic Gonadotropin (HCG).
- An ultrasound examination determines the amount of tissue in the back of the baby’s neck (nuchal Translucency).
The first-trimester screening usually takes place between weeks 11-14 of pregnancy.
Your age, the ultrasound results and blood tests will help your doctor determine your chances of having a Down or Trisomy 18-year-old baby.
You might opt to continue first-trimester screening with a more definitive test if your risk level is high or moderate.
It’s possible because it is.
Screening is performed in the first trimester to assess your risk of having a Down syndrome baby. This test provides information on the risk of Trisomy 18.
Lifelong impairments in mental, social and physical development can be caused by Down syndrome. Trisomy 18 is more serious and can lead to death by the time you turn 1.
Screening for neural tube defects in the first trimester is not done during screening.
First-trimester screening is possible earlier than other prenatal screening tests. This means you will have your results sooner in your pregnancy. This will allow you to make informed decisions about the course of your pregnancy, medical treatment, and management after and during delivery. You’ll have more time to plan for special needs children if your baby is at higher risk for Down syndrome.
You can also have other screening tests done later in pregnancy. The quad screen is an example. It’s a blood test usually done between weeks 15-20 of pregnancy. The quad screen assesses your risk of having a baby with Down syndrome, trisomy 18, or other neural tube defects such as spinal bifurca. Some health care professionals combine the results from the first-trimester screening and the quad screen. This is known as integrated screening. This can increase the detection rate for Down syndrome.
Screening in the first trimester is not mandatory. The test results do not indicate if you are at greater risk of having a baby with Down syndrome, trisomy 18, or whether your baby has one.
Consider the implications of the results before you go to the screening. It would be best if you considered whether or not the screening is worth the anxiety and how you will manage your pregnancy differently depending upon the results. Consider whether the risk level is high enough to allow you to opt for a more invasive test.
There are risks
Routine prenatal screening for the first trimester is possible. There is no risk of miscarriage or other complications during pregnancy screening.
How to prepare
Preparing for the first-trimester screening is not difficult. Before the ultrasound exam and blood test, you can eat and drink normally.
What to expect
Screening for the first trimester includes a blood draw and an ultrasound exam.
A healthcare team member will take a blood sample from you by inserting a needle in a vein on your arm. The lab will analyze the blood sample. The lab will analyze the blood, and you can immediately return to normal activities.
You will lie on your stomach on an examination table for the ultrasound exam. A transducer, a small plastic device that transmits and receives sound waves, will be placed over your abdomen by either your health care provider or an ultrasound technician. Digitally, the reflected sound waves are converted into images using a monitor. Your health care provider or technician will use these images to measure the amount of tissue at the back and neck of your baby.
You can return to your normal activities immediately, as the ultrasound isn’t painful.
