First trimester screen is a noninvasive test  that combines maternal screening with ultrasound evaluation. This new optional procedure identifies the risk of the fetus for chromosomal abnormalities such as Down syndrome . A portion of this test known as nuchal translucency may be able to identify significant fetal abnormalities such as cardiac disorders. The first trimester screen does not however detect neural tube defects.

first trimester screen

You should note  that getting positive results  does not mean your baby has the condition. It only means further investigation and testing is needed to be able to make a diagnosis. The first trimester screening should not be confused with second trimester screening test such sa Quad screen and Triple screen. These screening tests  are performed around pregnancy week 15 to 20 and are less accurate.


The blood screen part of the first trimester screen measures 2 pregnancy hormones hCG and PAPP-A. The ultrasound measures the fluid beneath the skin behind the baby’s neck.


This screening test  combines the blood tests, ultrasound and mother’s age to determine the risk factors.


How is the first trimester test performed ?


Blood is drawn from the mother. This takes about 5 to 10 minutes. The blood is then sent to the lab   for testing. The ultrasound part take about 20 to 40 minutes. The results are back in about  a week of testing.


When is the first trimester screen performed ?


It is performed between 11 to 13 weeks of gestation. This test is performed early thereby helping doctor determine whether the mother needs to go for a second trimester diagnostic test such as amniocentesis or chorionic villus sampling.


Are there any risks ?


There are no risks associated with this screening test. You may have a discomfort at the site where the blood was drawn.


What does the first trimester screen test look for ?


Abnormally high or low hCG and PAPP-A levels are  usually found in children with chromosomal abnormalities. There is also an increased fluid found in the nuchal translucency. These results in combination with maternal age are used to determine the mothers risk for chromosomal abnormalities in her unborn child.


What do the result of the first trimester screen mean ?


This test is a screening test not a diagnostic test. It only identifies a mother’s risk of having a baby with chromosomal abnormalities. A normal result means there is no potential risk for chromosomal abnormalities in your bay. An abnormal result means there is a chance that your baby could have some chromosomal abnormalities. This means further testing is required to make a diagnosis.


The decision to have further testing is based on the individual. However having further investigation done gives you the chance to prepare physical and emotionally to care for a child with special needs.


Some people may opt out of further testing due to personal, moral, or religious reasons. It is better to discuss with your doctor the benefits and risks of this test.

Content Sources
First semester screening. American Pregnancy Association. Accessed January 5, 2015

First semester screening for birth defects. WebMD. Accessed January 5, 2015

Screening tests for birth defects. The American College of Obstetricians and Gynecologists. Accessed January 5, 2015


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