Distribution of Normal Nuchal Translucency Thickness: A Multicenter Study in Thailand

Abstract

Aims: To establish the normative data distribution of nuchal translucency (NT) thickness in Thai fetuses. Methods: A cross-sectional multicenter study was conducted among 6,455 women with singleton pregnancies and gestational age between 10 and 14 weeks. For each case, the fetal crown-rump length (CRL) and NT were measured by transabdominal ultrasound. Transvaginal ultrasounds were used in poorly visualized cases. The distribution values of the NT thicknesses and their corresponding 10-mm CRL intervals between 45 and 84 mm were examined to obtain the median and 95th percentiles. Quantile regression modeling across the CRLs was performed to obtain the reference values. Results: Transabdominal ultrasound measurements were successfully done on 6,347 fetuses with 39 cases by the transvaginal route. Fetuses with CRL between 45 and 84 mm and normal outcomes made up a total of 4,352 cases. The mean (SD) gestational age, CRL and NT thickness were 12.5 (0.7) weeks, 60.2 (9.7) mm, and 1.15 (0.38) mm, respectively. The mean normal NT increased linearly with CRL. The quantile regression equation to predict the 95th percentile of the NT thickness (mm) was 0.727 + [0.017 × CRL (mm)]. Conclusions: The NT thickness in normal Thai fetuses was found to be thinner than in both Caucasian and other Asian populations.

Reference values of nuchal translucency thickness in a Brazilian population sample: experience from a single center

“…An increase in NT thickness was observed in our study, tending to stabilize at CRL of 70 mm or greater. Comparing with studies carried out with other populations, both visual analyses of dispersion graphs and of means was very similar in European [8,15] and Asian individuals [7,8].…”

“…Several studies have determined reference values for NT thickness in different populations; however these investigations addressed European [10,15] and Asian populations [4,7], which are predominantly homogeneous, hindering checking the ethnic factor in NT thickness. An increase in NT thickness was observed in our study, tending to stabilize at CRL of 70 mm or greater.…”

“…Reference curves were described for NT thickness at 11-14 weeks of gestation in different world groups [4,7], but the great majority are homogeneous populations, which hinders evaluating the real effect in measuring NT thickness. In the census conducted in the year 2000, for a total of 168,200,000 inhabitants, the Brazilian population comprised 53.7% white; 7.7% black and 38.6% of miscegenated individuals (white, black and indigenous).…”

Normative weight-adjusted models for the median levels of first trimester serum biomarkers for trisomy 21 screening in a specific ethnicity

“…In addition, the combination of serum biomarkers and the use of NT is recommended in risk estimation to give better specificity. As our center have defined normative data for NT thickness in each gestational week and the 95th percentile value for a given gestational age in the Thai population [13]. This study may add more sensitivity for first-trimester combined screening for trisomy 21 in our population.…”

‘Normal’ nuchal translucency: a justification to refrain from detailed scan? Analysis of 6858 cases with special reference to ethical aspects

“…9 The list of anomalies that can be found in fetuses with 'increased' NT has become long. [8][9][10] From a medical and an ethical point of view, an important question is: what is the number of major anomalies we miss if we restrict detailed scan to fetuses with 'increased' NT defined as NT exceeding the 95th centile [11][12][13][14][15][16][17][18][19][20][21] and neglect anomalies present in the subgroup of fetuses with 'normal' NT, which includes 95% of all fetuses? Common sense, supported by objective studies, tells us that parents want to know about any fetal problems as early in pregnancy as possible.…”