Is nuchal translucency a useful aneuploidy marker in fetuses with crown-rump length of 28-44 mm?

To investigate whether increased nuchal translucency (NT) in fetuses with a crown-rump length (CRL) below 45 mm needs to be re-evaluated at a later stage, or whether the early NT measurement can be used effectively as an aneuploidy marker.

This was a prospective cohort study including all singleton fetuses with a CRL between 28 and 44 mm, scanned in our center during 2002-2012. The CRL, NT, fetal karyotype (when available) and pregnancy outcome were recorded. NT reference ranges were constructed using the Lambda-Mu-Sigma (LMS) method in non-referred pregnancies after exclusion of chromosomal anomalies. The 95(th) percentile was used to calculate detection rates for chromosomally abnormal fetuses.

NT was successfully measured in 643 of 672 fetuses with a CRL of 28-44 mm. Subsequent cytogenetic analysis revealed 11 cases of trisomy 21, 14 cases of trisomy 13 or 18, three cases of monosomy X, three sex trisomies, three triploidies and 12 balanced anomalies. NT was above the 95(th) percentile in 64% of the fetuses with trisomy 21, in 71% with trisomy 13 or 18 and in all three cases of monosomy X.

NT appears to be useful as a marker for the early detection of fetal trisomies at 9-10 weeks' gestation (28-44 mm CRL).