(ThySistas.com) Prenatal screening provides information about your health and the health of your baby. The results of these tests allow doctors to analyze the likelihood that your child will be born with a birth defect or with a chromosomal abnormality.
Why Consider Prenatal Screening?
Although all women are offered prenatal screening, there are certain women who may benefit more from the results. You may want to consider prenatal screening if:
● You are of advanced maternal age of 35 years or older
● You have previously given birth to a child with a birth defect or a chromosomal abnormality
● You have a family history of chromosomal abnormalities
● You have a chronic medical condition such as diabetes or high blood pressure
When Can Prenatal Screening Be Performed?
Prenatal screening can be performed either during the first trimester or during the second trimester. There are restrictions for differing types of tests as to when they can be performed. Speak 
with your doctor to understand which test is appropriate depending on how far along you are in your pregnancy.
First Trimester
Prenatal screening during the first trimester can begin as early as week 10 in your pregnancy and is typically performed during weeks 11-14. During this time, screening typically involves ultrasound imaging and tests performed using a blood draw. These test options monitor the development of the fetus as well as the risk that may exist for chromosomal abnormalities. Additionally, physical defects and developmental progress are observed during this time.
Second Trimester
Prenatal screening during the second trimester can begin as early as week 14 in your pregnancy and is typically performed between weeks 14-18. These tests may include ultrasound imaging and blood tests using a sample from the mother. Doctors perform these screenings during the second trimester to monitor the risk of Down syndrome or a neural tube defect in the fetus.
Types of Prenatal Screening
Prenatal DNA testing – Prenatal DNA testing is a non-invasive test used to determine if there is a risk that the fetus has trisomy 21 (Down syndrome), trisomy 18 (Edwards’ syndrome), or trisomy 13 (Patau syndrome). This test can be performed as early as week 10 in your pregnancy using a simple blood draw from the mother. Prenatal DNA testing offers more information about your pregnancy without the risks associated with invasive prenatal procedures.
Nuchal translucency ultrasound – A nuchal translucency ultrasound uses ultrasound imaging to measure the thickness of the nuchal translucency in the fetus. Nuchal translucency is fluid located underneath the skin at the back of the fetus’ neck. If the amount of fluid measured is more than typical, this may indicate a genetic disorder or a heart defect. Nuchal translucency ultrasound can be performed between gestational weeks 10 and 14.
Maternal serum screening – Maternal serum screening is often referred to as the triple or quad screen test. The triple screen and quad screen tests are performed during the second trimester, typically between weeks 16 and 18 in the pregnancy. The triple screen test analyzes three specific proteins and hormones found in the mother’s blood, while the quad screen test analyzes four. The levels of these specific substances are examined in order to determine if there is a risk that the fetus has Down syndrome or trisomy 21.
Where Can I Find More Information?
Genetic counselors are trained healthcare professionals that analyze your health, along with your family medical history, in order to determine the risk of giving birth to a baby with a genetic condition. They can also present prenatal screening options as well as help you understand prenatal test results. Prenatal screening is your choice. Speak with a genetic counselor to learn more about your options.
Resources:
http://www.healthline.com/health/pregnancy/prenatal-testing#Overview1
http://sogc.org/publications/prenatal-screening/
http://www.health.wa.gov.au/docreg/Education/Prevention/Genetics/HP3131_prenatal.pdf
http://www.advancedwomensimaging.com.au/nuchal-translucency-ultrasound
http://www.babycenter.com/0_quad-screen-second-trimester-prenatal-screening_1487.bc?showAll=true
http://americanpregnancy.org/prenatal-testing/quad-screen/
http://www.mayoclinic.org/tests-procedures/first-trimester-screening/basics/definition/prc-20014597
http://www.babycenter.com/0_prenatal-genetic-counseling_1607.bc
Staff Writer; Krissy Lewis