Supplementary Material for: Lung hypoplasia in Fetuses with Skeletal Dysplasia Determined by Fetal Lung Weight. Which Ultrasound Measurement/Ratio Has the Highest Detection Rate

Introduction To determine lung hypoplasia in cases with fetal skeletal dysplasia based on the total lung weight at autopsy as the most accountable surrogate marker for pulmonary hypoplasia. Methods This retrospective cohort study included all pregnancies with antenatal diagnosis of skeletal dysplasia(2012-2018). We included only cases in which information on fetal biometry was available within 2 weeks before delivery and had autopsy and skeletal X-rays+molecular analysis using extracted fetal DNA. We compared the predictive accuracy of fetal sonographic body-proportional ratios including:(1) thoracic circumference-to-abdominal circumference(TC/AC) ratio, (2)the femur length-to-abdominal circumference(FL/AC) ratio, (3)head circumference-to-abdominal circumference(HC/AC) ratio, and (4)foot length-to-femur length ratio. Lung hypoplasia was defined as total lung weight below -2SD from the expected mean for gestational age. Results 53 pregnancies with antenatal diagnosis of skeletal dysplasia underwent autopsy included. Lung hypoplasia was determined in 34(64.1%). Median of gestational age at last sonographic assessment was 21.3(19.9-24.9) weeks. FL/AC ratio demonstrated the highest area under the curve of 0.817(95%CI:0.685-0.949;p<0.0001). FL/AC≤0.1550 demonstrated the highest detection rate of 88.2% along with the highest negative predictive value(NPV) of 75%. Discussion/Conclusion Using a novel, more practical approach to predict lung hypoplasia in skeletal dysplasia, fetal sonographic body-proportional ratios and, specifically, FL/AC ratio demonstrate a high detection rate of lung hypoplasia.