OP34.04: Fetuses with single umbilical artery: a seven year study

Abstract

Short oral presentation abstracts for Down-syndrome. We prospectively measured and compared prenasal soft tissue thickness (PT) and nasal bone length (NBL) in second trimester euploid and trisomy-21 fetuses. Methods: Using 2D abdominal ultrasound the measurement of PT and NBL was taken in mid-sagittal plane of the fetal head identifying diencephalon, tip of the nose, lips, maxilla, mandible, nasal bone in weeks 16-23 in the second trimester. The PT is the shortest distance from the bottom edge of the os frontale to the outer surface of the overlying skin. The nasal bone was measured from this view. The insonation angle was 90 • (perpendicular) to the nasal bone. NBL/PT ratios of euploid fetuses between 16-23 weeks were analyzed and validated by Shapiro-Wilke test. We used software (SigmaStat 12 & SigmaPlot 12) to create graphs, the regression line and the percentiles curves (5 th-25 th-75 th-95 th) have been calculated from the normal values. We used the normal graphs to visualize and compare trisomy 21 cases to euploids (P < 0.0001). Results: Analyzes of 810 euploid and 19 fetuses with trisomy 21 measured between the 16-23 gestational weeks were done. In euploid fetuses the mean PT and NBL increased steadily between 16 and 33 weeks' gestation. The difference in the median PT values between the two groups was greater than would be expected by chance. There was a statistically significant difference (P = <0.001) Mann-Whitney Rank Sum Test. All of the 19 fetuses with trisomy 21 the NBL/PT values were lower than 5 th percentile curve of the euploid group. Conclusions: CIn fetuses with trisomy 21 the NBL/PT ratio was significantly lower compared to euploid ones. The NBL/PT ratio was found to be very sensitive and specific marker for trisomy 2.