Fetal Nasal Bone Length Measurement

Why Is This Test Done?

Your healthcare provider may recommend this test if you are at higher risk for conditions like Down syndrome, trisomy 13, or other chromosomal abnormalities. It is sometimes included in first-trimester screening, especially if you have risk factors such as advanced maternal age, family history of genetic disorders, or other medical conditions. This test is typically performed between 11 and 14 weeks of gestation using an ultrasound to visualize the fetal nasal bone.

How Is the Test Performed?

During the ultrasound, a transducer is placed on your abdomen to create images of your fetus. The provider will measure the length of the nasal bone, which appears as a small bony structure near the nose. This measurement is compared to standard ranges to determine if it falls within expected limits or if further evaluation is needed.

What Does the Result Mean?

A fetal nasal bone length that is shorter than expected may be associated with an increased risk of certain chromosomal conditions. However, it is not a definitive test for these conditions. Your provider will discuss the results with you and may recommend additional testing, such as amniocentesis or chorionic villus sampling, if needed. Results alone do not diagnose a condition; they are used as part of a broader evaluation.

What Are Possible Outcomes?

If the nasal bone length is within normal limits, it suggests no increased risk for the conditions being screened. If it is outside the normal range, further genetic counseling and testing may be advised to assess risks more thoroughly. This test is not diagnostic but is part of a screening process to identify potential concerns early.