Changes of Nuchal Translucency in Early Normal Fetuses

Park, Jin Wan; Lee, Won Ki

Abstract

OBJECTIVE
To examine a normal range for nuchal translucency thickness between 9 and 14 weeks' gestation in normal fetuses.
METHODS
Nuchal translucency was measured prospectively in 124 fetuses between 9 and 14 weeks' gestation resulted in normal pregnancy outcome. The nuchal translucency measurement was expressed as the median and the 5th, 25th, 75th, and 95th percentiles according to complete weeks of gestation based on ultrasound measurement.
RESULTS
The median nuchal translucency thickness was 1.8 mm at 9 weeks' gestation and it declined to 1.6 mm at 10 weeks. But the median thickness increased from 1.95 mm at 11 weeks to 2.3 mm at 12 weeks, after which it slightly declined to 2.25 mm at 13 weeks. And then it increased to 2.5 mm at 14 weeks. A nuchal translucency thickness greater than 2.5 mm was not found at 9 and 10 weeks' gestation, but found in 21.8% of fetuses from 11 weeks to 14 weeks.
CONCLUSION
In normal fetuses, there is a physiologic variation in the thickness of nuchal translucency between 9 and 14 weeks' gestation. The calculation of risk for trisomies based on this thickness should take this variation into account. The adoption of a gestational age-dependent cutoff point, based on the deviation of a given measurement from the median, may reduce the invasive procedure for karyotyping. And this study suggest that if the nuchal translucency measurement is greater than 2.5 mm before 10 weeks, it may advise the karyotyping.