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Reference values of nuchal translucency thickness in a Brazilian population sample: experience from a single center
Objective:
To determine the reference values of nuchal translucency (NT) thickness at 11-14 weeks of gestation in a sample of the Brazilian population.
Methods:
A retrospective cross-sectional study was carried out with singleton gestations and fetuses with a crown-rump length (CRL) of 45-84 mm. NT thickness was performed according to the guidelines of the Fetal Medicine Foundation (FMF), London, UK. To evaluate the correlation between NT thickness and gestational age (GA), polynomial equations were calculated, with determination coefficient (R2) adjustments, as proposed by Altman-Chitty.
Results:
A total of 1420 pregnancies were assessed. The mean of the gestational age was 12.69±0.78 weeks. The mean maternal age was 28.78±6.81 years. The mean NT thickness (mm) for the CRL intervals of 45├50; 50├55; 55├60; 60├65; 65├70; 70├75; 75├80; 80├85 was 1.30±0.74; 1.34±0.60; 1.48±0.48; 1.56±0.68; 1.71±0.67; 1.78±0.69; 1.67±0.43; 1.67±0.58; respectively. The following second-order equation best represented the correlation between NT thickness and GA: NT=-1.2570+0.0765×GA-0.0005×GA2 (R2=0.05).
Conclusion:
The reference values for NT thickness were determined for a sample of the Brazilian population. Further studies are required to evaluate the real need for including these values in first-trimester screening for chromosomal defects in Brazil.
