Your labor and delivery team have two priorities at the heart of their services –those are to ensure both you and your baby are safe and healthy. In order to facilitate those goals, we provide all kinds of prenatal tests designed to reduce the risk of pregnancy and delivery complications.
You can visit, Keeping Track of Baby’s Health: Prenatal Testing to read a general overview of prenatal tests and procedures, which include:
- Routine Tests
- Screening Tests
- Diagnostic Tests
- Monitoring Tests
What Are Screening Tests?
Screening tests are typically performed as your pregnancy progresses. From them, we can glean more specific and intimate details regarding your baby’s development, how your uterus and placenta are holding up, and other factors will determine whether or not we recommend further diagnostic testing or if we feel something requires a little more attention.
It is important to note that results of these screening tests are never 100% accurate. Some mothers who have completely normal tests may still have a baby with some type of abnormality, and some mothers who receive abnormal test results give birth to perfectly healthy babies. Prenatal screening tests are simply used as a guide, and to help mothers – and their birth teams – prepare for potentially abnormal scenarios.
7 Common Screening Tests
The 7 most common prenatal screening tests are:
Ultrasounds. Also called sonography, ultrasounds are the parents’ favorite type of screening test because they let you have an up close look at that sweet fetus as it grows, changes and begins to resemble the sweet baby that you will give birth to before you know it. Ultrasounds use gentle sound waves to provide digital feedback regarding the contours of your inner-abdomen. That feedback creates a visual representation that can be viewed on a monitor.
Unless you specify otherwise, ultrasounds are used throughout the pregnancy. In the beginning, we want to make sure the baby’s development is on track. It is used to determine whether you have one baby in there, or whether you’re carrying twins. If you start to bleed during your pregnancy, an ultrasound will often reveal the cause and determine whether action is required or not.
As your pregnancy progresses, an ultrasound will be used to get a more accurate idea of your due date. I can also reveal the baby’s sex, amniotic fluid levels, and certain birth defects.
Nuchal Translucency Screening (NTS). This is a non-invasive test performed using an ultrasound during your first trimester. It determines the measurement of fluid present in the skin fold along the back of your baby’s neck. Combined with a blood test from the mother, it can show whether there are any chromosomal abnormalities.
Multiple Marker Genetic Screening. In the past, women 35-years and older were advised to use genetic screening – via amniocentesis or chorionic villus sampling (CVS) – because they were at higher risk for having a baby with chromosomal abnormalities, the most common of which is Down’s Syndrome. Now, however, medical innovations have led to blood, ultrasound and NTS tests, which can identify Down’s Syndrome and other chromosomal abnormalities using a second-trimester blood draw.
These are called TriScreen or QuadScreen tests. Unfortunately, they are inaccurate 5% of the time, so further diagnostic testing is recommended if/when the results are abnormal.
Alpha-Fetoprotein Test (AFT). Currently, this is an optional blood test, typically offered between 16- and 18-weeks of pregnancy. It can be done alone or along with the TriScreen or QuadScreen tests. It is done to identify potential neural tube defects, indicating problems with brain or spinal cord development. The most common of these rare defects are anencephaly or spina bifida.
However, a “normal” reading of this test is no guarantee; as many as 20% of babies born with neural tube have normal alpha-fetoprotein levels. Similarly, 50 out of every 1000 women will be told the results were abnormal, but only one or two of those women will actually have a baby with a neural tube defect. Abnormal results will typically mean you need to have a second test performed to see if the results are the same.
Cell Free Fetal DNA. This is one of the newest screening tests available and it is lauded due to its non-invasive nature and reliable results. Unfortunately, because it is new, it is still very expensive and most insurance companies do not cover the costs. Therefore, it’s not recommended for younger mothers with low-risk pregnancies.
The test is done using a blood draw from the mother at 10-weeks. At this point in pregnancy, some of the baby’s DNA has spilled into the mother’s bloodstream via the placenta. It is used to test for chromosomal abnormalities, like trisomy 18, trisomy 21 and trisomy 13, and it can also identify certain other chromosomal issues dealing with a missing or additional chromosome.
If the test is negative, most women can skip more invasive screening tests – such as amniocentesis and CVS.
Cystic Fibrosis (CF) Carrier Testing. Cystic Fibrosis is a serious disease that results in abnormal mucous production in the lungs and digestive tract. While medications are available to treat the disease, it usually worsens with age and most individuals with CF do not live past their 40s. It requires one gene from each parent for an individual to have CF, and risk factors are higher in certain ethnicities and/or those with a family history of CF.
If a mother tests positive, it’s recommended the father be tested too. If the father tests positive for the gene, CVS or amniocentesis will be recommended for the fetus to see if it has both genes. Even in cases where both parents carry the gene for CF, only 1 in 4 babies will be born with CF.
Fetal Fibronectin Test (fFN). This test can be done between the 22 and 35-week stages, using a swab of the mother’s vaginal secretions. It can indicate whether a mother is likely to go into preterm labor. Fetal fibronectin tests are not routine, and is recommended in special circumstances where doctors suspect a woman is at risk for preterm labor.
Again, we want to emphasize that these test are:
- Have risks and benefits
- Are not 100% conclusive
Have a heart-to-heart conversation with your doctor to determine which of these tests, make the most sense for you and your baby.
Feel free to contact Overlake OB/GYN to schedule your first prenatal appointments and we’ll be happy to steer you in a safe and sensical direction when it comes to screening tests and your baby’s health.
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