P64The newly calculated equations of nuchal skinfold thickness measurement in mid‐trimester

Abstract

BackgroundUse of nuchal skinfold thickness (NT) measurement as an ultrasound marker for Down syndrome has been limited due to a high false positive rate. We suggested that some variables, which influence on NT have been presented. The purpose of our study was to identify the variables that have effects on measured values of NT, and to make a regression equation based on those variables.MethodThe data on gestational age (GA), cephalic index (CI), presentation (Pr; vertex or breech) and the presence or absence of nuchal cord (NC) were collected prospectively on 548 normal singleton fetuses between 16 and 24 weeks' gestation. We calculated independent correlation of those variables with NT by multiple regression analysis and made a regression equation based on GA, CI, Pr, and NC.ResultsGA has positive correlation and CI has negative correlation with NT significantly. The nuchal skinfold was thicker among fetuses with breech presentation rather than those of vertex presentation and increased in the presence of nuchal cord. The all four variables (GA, CI, Pr, and NC) were independent factors to NT by multiple regression analysis.We calculated the expected NT through these observations; for fetuses presenting vertex, NT = 5.608 + 0.243GA − 0.066CI + NC* and for breech, NT = 2.803 + 0.392GA − 0.066CI + NC* (*if no NC, NC* equals −0.785 and zero for the other).ConclusionThis is the first report, which takes GA, CI, Pr and NC for correlation factors with NT as a whole. These equations may be considered as a screening method for the detection of aneuploidies.