[Distribution and normal reference range of fetal nuchal translucency thickness in Kunming pregnant women in the first trimester].

Objective: To establish the normal reference range of fetal nuchal translucency (NT) thickness in Kunming Chinese pregnant women in the first trimester.

Methods: The study samples comprised of 1790 Kunming pregnant women who attended antenatal visit in the first trimester in the First Affiliated Hospital of Kunming Medical University. The general information including maternal date of birth, past pregnant history and other related conditions were recorded. The crown rump length (CRL) and NT thickness at 11 - 13(+6) gestational weeks were measured according to guidelines from Fetal Medicine Foundation (FMF).

Results: The total 1790 of normal fetuses was recruited for final analysis. The mean and median values of CRL were (59.6 ± 9.2) mm and 58.3 mm, respectively. The mean and median values of NT thickness were (1.7 ± 0.5) mm and 1.7 mm, respectively. While the CRL were at between 45.0 - 54.9 mm, 55.0 - 64.9 mm, 65.0 - 74.9 mm and 75.0 - 84.0 mm, the corresponding values of NT thickness were 1.0 mm, 1.3 mm, 1.5 mm, 1.5 mm at the 5(th) percentile and 2.0 mm, 2.5 mm, 2.7 mm, 2.9 mm at the 95(th) percentile, respectively, and the corresponding medial values of NT thickness were 1.4 mm, 1.7 mm, 2.0 mm, 2.0 mm, respectively. The NT thickness had no relationship with maternal age (P > 0.05). The mean value of NT thickness was (1.8 ± 1.1) mm in male fetuses. The mean value of NT thickness was (1.7 ± 0.6) mm in female fetuses. The NT thickness in male fetuses was significantly thicker than that of females (P = 0.001).

Conclusion: The present study established a reference range of normal fetal NT thickness corresponding with CRL in early pregnancy with reliable FMF quality control.