Prenasal thickness‐to‐nasal bone length ratio: a strong and simple second‐ and third‐trimester marker for trisomy 21

Abstract

Objectives To study the ratio of prenasal thickness (PT) to nasal bone length (NBL) in normal and trisomy-21 fetuses in the second and third trimesters of pregnancy.Methods The PT and NBL were measured retrospectively in 106 normal fetuses (in three-dimensional (3D)

Trends in Serial Measurements of Ultrasound Markers in Second and Third Trimester Down Syndrome Fetuses

“…Longitudinal trends in individual markers measured in DS fetuses are presented in figure 1, along with the mean measurement in normal fetuses [8,14,19,23]. …”

“…Data were compared with the reference values derived from our previous reports on euploid fetuses [14,19] or compared with reference values derived from the literature [8,9,22,23]; the NBL and PT increased with gestation from 3.3 mm at 15 weeks' gestation to 9.6 mm at 33 weeks (NBL = -6.927+(0.83*GA)-(0.01*GA 2 )) and from 2.3 mm at 15 weeks to 6.1 mm at 33 weeks (PT = 0.212 × GA − 0.873), respectively. The PT-NBL ratio and PFSR were stable throughout gestation, with a mean of 0.61 (95th centile = 0.80) and 0.97 (5th centile = 0.55), respectively.…”

“…Short nasal bone length (NBL), increased prenasal thickness (PT), and increased nuchal fold thickness (NF) are the most frequently investigated [1,2,3,4,5,6,7,8,9,10,11,12]. Recent studies have indicated that the use of ratios, such as the prenasal thickness to nasal bone length ratio (PT-NBL ratio) and the prefrontal space ratio (PFSR), are strong and easy-to-use second-trimester markers [13,14,15]. …”

“…In a recent study, we have demonstrated that the NBL, PT, PT-NBL ratio, and PFSR are valuable and reproducible DS markers [13,14,19] and assessed the detection rates, which appear to be evenly distributed throughout the second and third trimester. However, these studies were based on cross-sectional measurements in both normal and DS fetuses.…”

New aspects and the integration of the first and early second trimester screening to the feto-maternal medicine

“…The latest screening strategy for first and second trimester was introduced by Nicolaides et al ( 51,53,60,65,69,70,[74][75][76][77][78][79][80][81][82][83] CRL, BPD, FHR and FL were measured from the beginning of the obstetric ultrasound era.…”