First trimester testing provides early-stage information about the health of your pregnancy by combining comprehensive ultrasound and blood testing.
First trimester screening ultrasounds are performed between the 11th and 13th week of pregnancy depending on the size of your baby. Blood testing can be done during either your first ultrasound visit or two weeks prior.
Having the tests done two weeks prior to the ultrasound means that results will be on hand in case of an abnormal ultrasound. However, most women find it more convenient to have their first trimester screening completed in one visit.
What Can the Blood Test Tell Me?
First trimester blood tests measure concentrations of pregnancy-associated plasma protein A (PAPP-A), and free-beta human chorionic gonadotropin protein (free ß-hCG). During pregnancy, these two proteins enter the bloodstream as serums necessary for normal fetal growth.
Reduced levels of PAPP-A and free ß-hCG may suggest the baby is suffering from chromosomal abnormalities indicative of Down’s or Edward’s syndromes. Your age is also taken into consideration when assessing results from your first trimester testing.
Women over the age of 35 experience an increased risk for giving birth to a child with Down syndrome, Edwards syndrome, or Patau syndrome. Discuss your risks with your gynecologist if you are over the age of 35 and planning to become pregnant.
What Can the Ultrasound Tell Me?
Ultrasound examinations can reveal the presence of fetal bones and measure their development. Underdeveloped fetal nasal bones can be indicators of possible Down syndrome because children with Down’s have poorly developed sinus cavities and narrow nasal passages.
Your ultrasound also shows nuchal translucency, which is a collection of fluid under the skin at the back of your baby’s neck. Nuchal translucency scans measure how much “translucent,” or clear space exists at the back of the fetal neck. If excess fluid accumulates in this area during the first trimester, it may indicate that the baby has one or more chromosomal abnormalities.
Who Should Have a First Trimester Screening?
First trimester screening is a safe and noninvasive procedure. It is highly recommended—though not mandatory—for all pregnant women. However, women with a higher risk of birthing a child with chromosomal disorders should be screened. If you meet any of the following risk factors, you are strongly urged to undergo first trimester testing:
- You are 35+ years old. Older eggs are at risk for experiencing improper division of chromosomes at conception. About one in 350 women between the ages of 35 and 40 give birth to a Down syndrome baby. At age 40, the risk climbs to one in 100.
- You already have a child with Down syndrome.
- You carry the Down syndrome “gene.” Both women and men can pass on the genetic translocation needed to produce Down syndrome in their children, so get tested if you or your partner carry the gene.
What If the Tests Are Abnormal?
Remember that first trimester testing is not a diagnostic test, but a screening test. It only indicates your risk—not certainty—of carrying a child with a genetic disorder. In fact, many abnormal fetal screenings prove false with additional testing.
If your results are abnormal, or if you are at high risk for the chromosome mutation that causes Down syndrome, your obstetrician may suggest testing with cell free fetal DNA. This chromosome selective sequencing technology identifies approximately 98% of cases of Down syndrome with a false-positive rate of less than 0.5%.
Cell free fetal DNA testing is not recommended unless you are high-risk and pregnant with your first child, or if the results of the previous tests are abnormal.
Your obstetrician will talk to you about your test results, answer any questions you have, and address your concerns about the risk factors of your pregnancy. If your test results are concerning, you may be referred to a genetic counselor who can help you make the best decision for your health and family.
If you have recently become pregnant, contact The Woman’s Clinic to set up first trimester testing. Call (501) 664-4131 to make an appointment today.
*The Woman’s Clinic does not perform nuchal translucency testing and may refer you to a partnering hospital if further testing is required