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Updated: Apr 28, 2026
Murine Fetal Echocardiography
Published on: February 15, 2013
Increased Nuchal Translucency in Fetuses With a Crown-Rump Length of < 45 mm: Clinical Outcomes and Diagnostic
Philipp Kreiselmaier1, Makis Papadopolous2, Jochen Ritgen2
1Centre of Prenatal Medicine, Amedes Experts, Hamburg, DEU.
Background/Objectives:
Nuchal translucency (NT) measurement is an established first-trimester screening tool for chromosomal abnormalities. However, standardized risk assessment models are only validated for fetuses with a crown-rump length (CRL) between 45 and 84 mm. This study investigates the clinical significance of increased NT in fetuses with a CRL between 35 and 45 mm.
Methods:
This retrospective study analyzed 208 singleton pregnancies with a CRL < 45 mm and an NT ≥ 2.5 mm, examined at two tertiary prenatal centers between 2008 and 2024. Data on chromosomal findings, structural anomalies, and pregnancy outcomes were collected through follow-up. Statistical analyses included univariate, bivariate, and receiver operating characteristic curve analysis to determine optimal NT cut-off values for predicting adverse outcomes.
Results:
Chromosomal abnormalities were present in 67/208 cases (32.2%), with trisomy 18 being the most frequent. Malformations were detected in 46.7% of cases with available follow-up. The optimal NT cut-off for predicting an abnormal karyotype was 3.89 mm (sensitivity 79.1%, specificity 55.3%). Among fetuses with NT ≥ 5.5 mm, the rate of adverse outcomes reached 83.7%. Notably, 29.9% of chromosomal abnormalities would not have been detected by cell-free DNA screening for aneuploidy alone. Overall, the presence of increased NT, even below the standard CRL threshold, was associated with a significantly elevated risk of genetic and structural abnormalities as well as adverse pregnancy outcomes.
Conclusions:
NT measurement in fetuses with CRL < 45 mm provides clinically relevant prognostic information. Elevated NT in this early gestational window is significantly associated with chromosomal anomalies, structural defects, and poor pregnancy outcomes. Reliance on cell-free DNA screening for aneuploidy alone in this cohort may miss a substantial proportion of abnormal cases. Early NT assessment should prompt comprehensive diagnostic evaluation and genetic counseling, even when the CRL is below 45 mm.
