Prenatal screening tests are a set of procedures that are performed during pregnancy on expectant mothers to determine whether a baby is likely to have specific birth defects. Most of these tests are noninvasive. They are usually performed during the first and second trimesters, although some are performed during the third. A screening test can only provide your risk, or probability, that a particular condition exists. When the results of a screening test are positive, diagnostic tests can provide a definitive answer. Below is a list of screening tests offered by our office.
First trimester ultra-screen/instant risk assessment (IRA)
First-Trimester screening is a normal, reliable test used for early pregnancy evaluation. It consists of two parts:
1. ) A blood test, drawn from either your arm or your finger.
2. ) A detailed ultrasound examination of your baby.
The IRA program allows the earliest possible risk assessment for Down syndrome (Trisomy 21), Trisomy 18, and Trisomy 13.
By having your blood drawn at 10 weeks gestation, you will be able to get immediate results on the day of your ultrasound examination, which is carried out between 11.5 & 12.5 weeks gestation.
First trimester nuchal translucency screening
This is a genetic screening test that combines a patient’s medical history with ultrasound findings and laboratory test results. It is performed at the end of the first trimester of the pregnancy – usually between 11 and 13 ½ weeks gestation. The ultrasound involves the crown-rump length measurement of the fetus (a measure of the length of the baby from the top of the head to the baby’s bottom) with a measurement called a nuchal translucency thickness (the thickness of fluid on the back of the baby’s neck). The laboratory testing is a simple blood test that measures the concentration of two substances in the mother’s bloodstream. All of this information is then analyzed and a risk value for chromosome abnormalities is generated. This test will not tell a person that for sure everything is normal or abnormal – it is a screening test that provides a risk assessment. The meaning of the results will be fully explained once they return. This test involves no risk for the fetus or pregnancy. Results are usually available within a few days up to a week.
Early second trimester quad or triple screening or expanded alpha-fetoprotein (X-AFP) screening
This is a genetic screening test that combines a patient’s medical history and information with laboratory test results. It is performed early in the second trimester of the pregnancy – usually between 15 and 20 ½ weeks gestation. The laboratory testing involves drawing blood and measuring the concentration of 3 to 4 substances in the mother’s bloodstream. All of this information is then analyzed and a risk value for chromosome abnormalities is generated. This test also measures a substance called alpha-fetoprotein that is a screening test for certain birth defects, such as spina bifida or problems with the abdominal wall of the fetus. This test will not tell a person that for sure everything is normal or abnormal – it is a screening test that provides a risk assessment. The meaning of the results will be fully explained once they return. This test involves no risk for the fetus or pregnancy. Results are usually available within a few days up to a week.
Fetal magnetic resonance imaging (MRI)
This procedure involves performing a magnetic resonance scan (MRI) over the mother’s abdomen in the area where the baby is located. The mother is usually lightly sedated, which results in a light sedation of the fetus. MRI involves images obtained through large magnets – it does NOT use any radiation. This test is most often ordered to better define complicated or difficult to see birth defects identified by ultrasound. Fetal MRI is usually performed after the first trimester when the baby is already completely formed, therefore, there is minimal to no risk for the pregnancy.