Now that you know you are pregnant, you and your baby’s health will be carefully monitored throughout your pregnancy. Monitoring includes tests and screenings of both you and your baby to ensure optimal health and screen for potential risk of fetal abnormalities. One such test is a Nuchal Translucency (NT) Ultrasound.
What is Nuchal Translucency (NT) Ultrasound?
Nuchal Translucency (NT) ultrasound is a diagnostic prenatal screening assessment prescribed to detect chromosomal abnormalities associated with Down syndrome (trisomy 21), one of the most common genetic conditions affecting 1 in 700 U.S. babies each year. The screening also determines risk of Patau (trisomy 13) and Edwards (trisomy 18) syndromes, rare and often fatal chromosomal abnormalities.
The NT ultrasound is done between 11 and 13 weeks, when baby’s nuchal translucency, the clear tissue located at the back of a developing baby’s neck, can be measured. An average NT measurement is around 2.18 millimeters. Indications of a higher NT measurement during assessment increase the potential risk of fetal abnormalities being present.
It is worth noting that it’s not unusual for developing babies to have fluid or a clear space at the back of the neck. Additionally, studies have determined up to 13-percent of fetuses with normal chromosomal presentation reflect greater-than-average NT measurement of 2.5 millimeters. This test does not diagnose any of these chromosomal abnormalities. It will help your practitioner determine your risk and whether or not further testing is required.
What Can I Expect During Nuchal Translucency (NT) Ultrasound?
The screening, which requires a doctor’s referral, is noninvasive and uses an ultrasound wand on mother’s abdomen. A water-based gel is used on mother’s abdominal skin to transmit sound waves and facilitate probe movement. An alternative is a trans-vaginal test where the ultrasound probe is inserted into the vagina.
The accuracy rate of Nuchal Translucency (NT) ultrasound screening in identifying babies’ risk factors for chromosomal abnormalities is 70- to 75- percent when used as a standalone risk assessment with a five-percent false-positive rate.
Many doctors recommend pairing Nuchal Translucency (NT) ultrasound screening with two other types of blood screenings – the quad screen (known as integrated screening) or non-invasive prenatal testing (NIPT.) This improves identification of potential chromosomal abnormalities risk factors to 83- to 92-percent accuracy rate.
What Happens If I Have Abnormal NT Ultrasound Results?
The first thing to do is remain calm. An abnormal test result is a statistical likelihood, not a concrete diagnosis.
Talk to your doctor about additional testing options if chromosomal abnormalities are present. Two additional tests your doctor may recommend are amniocentesis or chorionic villus sampling.
Amniocentesis analyzes fluid drawn from the amniotic sac cradling the baby in the womb. The fluid, which contains cells providing baby’s genetic information, is taken via needle from the mother’s abdomen.
Chorionic villus sampling is when a placental tissue sample is taken and tested for potential chromosomal abnormalities and genetic issues.
Both amniocentesis and chorionic villus sampling do present small risks of miscarriage.
It’s important to note Nuchal Translucency (NT) ultrasound is a screening test and not a diagnosis and it is a recommendation, not a mandated test. . Some expectant moms skip testing to avoid knowing risk factors, especially if the outcome will have no bearing on their decision to continue on with the pregnancy. Talk to your doctor if you feel worried or anxious about how NT ultrasound results may affect you.
Discuss your family health history with your Capital Women’s Care team to determine if Nuchal Translucency (NT) ultrasound screening should be part of you and your baby’s prenatal health plan.