At what gestational age is a nuchal translucency scan usually performed?

A nuchal translucency scan is typically performed between 11 to 13 weeks of gestation. This specific timing is critical because during this period, the nuchal translucency measurement, which refers to the accumulation of fluid behind the neck of the developing fetus, provides valuable information for assessing the risk of chromosomal abnormalities, particularly Down syndrome.

The scan is part of first-trimester screening and is often combined with maternal blood tests to improve accuracy. The anatomical structures required for this measurement are most discernible during this period, making it the ideal time for the scan. After this window, the nuchal translucency becomes less relevant for early assessment as fetal growth and development continue, increasing the difficulty in obtaining accurate measurements.

Performing the scan too early, such as at 6-8 weeks, does not provide enough anatomical detail, while performing it later than 13 weeks, like in the 15-20 weeks or 24-28 weeks windows, falls outside the standard protocol for nuchal translucency assessment, which aims to identify risks early in pregnancy.