Screening for Open Spina Bifida in a Routine Clinical Setting at the First-Trimester Scan: A Prospective Multicentre Cohort Study

Abstract
Objective: The aim of this study was to investigate the performance of screening for open spina bifida (OSB) integrated into the routine first-trimester screening. Method: This is a prospective multicentre study of 4,755 women undergoing first-trimester ultrasound scans over a 4-year period. Measurements of the brainstem (BS) diameter and brainstem-to-occipital-bone (BSOB) distance were performed. The cisterna magna (CM) was measured in the tilted axial view. Results: Pregnancy outcome data were available for 4,658 fetuses included in this study. There were 5 fetuses with OSB, and in all of them, the BS/BSOB ratio and the CM measurements were abnormal. The sensitivity and specificity of a BS/BSOB ratio >1 were 100%. The sensitivity of a CM width Conclusion: Screening for OSB is feasible in routine first-trimester scans. The BS/BSOB ratio shows a very good sensitivity and specificity. In cases with near-normal values for the BS/BSOB ratio, the CM width might be helpful for further assessment.