First-trimester Screenings
“I’m having a baby!”
These words will be echoed by about four million expectant women in the United States this year. These words embody the dreams of many women. Pregnancy is a miraculous, beautiful, and exciting event in a woman’s life. As soon as women realize they are pregnant, however, they ask themselves another question:
“Will my baby be healthy?”
With advances in technology, the University of Kentucky Department of Obstetrics and Gynecology now offers first-trimester screening, a new test that provides earlier and more accurate information about the health of a fetus than previously available.
Screening options
First-trimester screening allows a woman to make informed decisions about more invasive tests, like amniocentesis (a test involving a needle placed into the woman’s uterus, using ultrasound guidance to obtain a sample of amniotic fluid), or chorionic villus sampling, CVS (an analysis of the genetic makeup of cells taken from the chorionic villi, which are tiny finger-like projections on the placenta).
Modern ultrasound allows the measurement of a very small area—only millimeters across—of fluid behind the neck of a fetus called the nuchal translucency, or NT. This measurement allows the physician to give the mother an assessment of the baby’s risk for Down syndrome and other chromosomal abnormalities.
Laboratories can also measure two proteins in the mother’s blood during the first trimester, Pregnancy Associated Protein (PAPP-A) and free beta human chorionic gonadotropin (hCG). These proteins are made by the fetal/placental unit.
By combining the ultrasound measurement with the blood test and other information about the mother, including her age, weight, and how far into the pregnancy she is, risk can be calculated for the most common chromosomal abnormalities.
It is important to remember these tests are not definitive, and other tests will be needed if preliminary results indicate your baby is at a high risk.
“The NT test allows a better detection rate about the health of your fetus without any risk to the pregnancy,” says Dr. Wendy F. Hansen, associate professor, UK College of Medicine, Department of Obstetrics & Gynecology.
What to expect with NT
The sonographer positions an ultrasound probe over the woman’s abdomen and measures the length of the fetus, confirming the gestational age. The sonographer then measures the thickness of the nuchal fold (area behind the neck) with calipers.
It may take up to 30 minutes to obtain an accurate measurement. The mother and her family can watch the entire ultrasound on a TV.
Next, a nurse draws the blood of the mother and asks a few pertinent questions. The results are generally back in one week. Most insurance policies cover the ultrasound and blood tests.
An expectant mother should be sure to discuss testing options with her partner, a clinician, and potentially a genetic counselor.
“First-trimester screening allows mothers more flexibility,” says Hansen. “Many mothers want as much information as possible with very little risk. Conversely, many mothers want to be prepared if the risk is thought to be high.”
If high-risk results?
If the test comes back with a high risk for a chromosomal abnormality, your physician will talk with you about CVS or amniocentesis.
“Both tests provide accurate information about the fetus but carry a very small risk of pregnancy loss,” says Hansen.
According to the Centers for Disease Control and Prevention, the risk of miscarriage due to amniocentesis is between one in 200 and one in 400, depending on the skill and experience of the doctor performing it. The risk of pregnancy loss due to CVS is about one in 100.
For more information about the benefits of NT, visit the UK Department of Obstetrics and Gynecology Web site at www.mc.uky.edu/obg.
