Nuchal translucency is the ultrasound appearance of a normal fluid-filled space between the back of the neck and the overlying skin of a fetus. It can be measured between 11 weeks + 5 days and 13weeks+6 days of gestation. A thick nuchal translucency, above the threshold of normal, may indicate a genetic difference in the fetus, including trisomy 21 (Down syndrome), trisomy 13, trisomy 18, or the presence of a body abnormality (for example in the heart). The thicker the nuchal, the higher the risk of any of these anomalies. However, it is important to know that the vast majority of fetuses with an increased nuchal translucency will be healthy babies.
Nuchal translucency ultrasound is safe and recommended for all pregnant patients in Ontario. At the time of the nuchal translucency, an early evaluation of fetal anatomy (skull, position of the heart, stomach, bladder, cord vessels, limbs) can be performed.
If the patient is interested in the risk assessment of chromosomal anomalies, the nuchal translucency is part of the parameters used for the enhanced first-trimester screening tests (eFTS). This means that the thickness of the nuchal translucency and blood test results are combined to provide a risk for the baby to have trisomy 21 or trisomy 18. Most people feel this test is helpful to reassure expectant parents that the baby is in good health.