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Nuchal translucency measurement in normal fetuses
E Pajkrt1, C M Bilardo, J M Van Lith
1Department of Obstetrics and Gynecology, Academic Medical Center, Amsterdam, The Netherlands.
Obstetrics and Gynecology
|December 1, 1995
Summary
Nuchal translucency measurements vary normally in fetuses between 9 and 14 weeks gestation. Accounting for this physiologic variation can improve the accuracy of trisomy risk assessment.
Area of Science:
- Prenatal diagnosis
- Fetal medicine
- Genetics
Background:
- Nuchal translucency (NT) is a key marker in first-trimester screening for fetal aneuploidies.
- Accurate NT measurement interpretation requires understanding normal gestational age-related ranges.
Purpose of the Study:
- To establish a normal range for nuchal translucency measurements.
- To define reference percentiles for NT in chromosomally and phenotypically normal fetuses from 9 to 14 weeks' gestation.
Main Methods:
- Prospective measurement of nuchal translucency in 771 chromosomally normal fetuses.
- NT measurements were analyzed to determine median, 5th, 25th, 75th, and 95th percentiles by completed weeks of gestation.
Main Results:
- The median NT increased from 0.7 mm at 10 weeks to 1.5 mm at 13 weeks' gestation.
- The incidence of NT > 2.5 mm increased from 4.6% at 10 weeks to 8.7% at 14 weeks.
Conclusions:
- Significant physiologic variation exists in NT measurements in normal fetuses between 9 and 14 weeks' gestation.
- Gestational age-dependent NT cutoffs, based on deviation from the median, can enhance trisomy risk assessment.
- Utilizing individualized NT thresholds may decrease false-positive results and reduce unnecessary invasive procedures.