Down’s syndrome screening at 11–14 weeks' gestation using prenasal thickness and nasal bone length
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To perform a multicenter prospective study of ultrasound prenasal thickness (PT), and nasal bone length (NBL) measurement at 11–14 weeks’ gestation.
Ultrasound PT and NBL determination was performed in 504 normal fetuses and 17 fetuses with Down's syndrome (DS). Measurements were made from mid-sagittal 2D images acquired using a standardized technique during nuchal translucency (NT) examination. PT and NBL values were expressed in multiples of the gestation-specific normal median (MoM) and as the PT/NBL ratio. Information on PT and NBL MoMs was also combined using logistic regression. Results were classified as positive according to whether they were greater than the normal 95th centile for PT, PT/NBL and the DS risk from logistic regression equation or below the 5th centile for NBL.
The median value in DS cases and unaffected controls were: PT 1.26 and 0.996 MoM; and NBL 0.596 and 0.993 MoM. The proportion of DS fetuses with positive results was 41% for PT, 65% for NBL, and 82% for both the PT/NBL ratio and DS risk from the logistic regression equation. PT/NBL levels did not vary according to gestational age.
The PT/NBL ratio is a valuable first trimester DS screening marker that can be easily determined concomitant with the NT measurement.
KeywordsFirst trimester Prenasal thickness Nasal bone length Down's syndrome Screening
GMB: project development, data collection, data analysis, and manuscript writing. RM: data collection and manuscript writing/editing. SS: data collection. HC: data analysis and manuscript writing/editing. UG: project development and manuscript editing. AG: project development, data collection, data analysis and manuscript writing/editing.
There was no funding for this study.
Compliance with ethical standards
Conflict of interest
The authors declare no conflicts of interest. The authors state that they had full control of all primary data and that they agree to allow the Journal to review their data if requested.
Ethical approval for the study was granted by the Ethics Committee of Central- and Northwest-Switzerland (EKNZ, Basel, Switzerland), No. 2016-01414. Approval was additionally obtained the two other participating centers (center 1: No. 053/17, center 2: No. 136/16). According to local regulations, informed consent was not obtained and not required for this anonymized data analysis. Patients were not included if they explicitly refused further use of their anonymized data.
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