Supplementary Material for: Isolated Cleft Lip and Palate: Maxillary Gap Sign and Palatino-Maxillary Diameter at 11–13 Weeks

<b><i>Objective:</i></b> To evaluate the maxillary gap sign and describe markers for the first-trimester diagnosis of isolated cleft lip and palate (CLP) at 11–13 weeks. <b><i>Methods:</i></b> Firstly, this was a prospective assessment of 1,087 fetuses including 5 cases of isolated CLP in 2 centers which were referred for the 11–13 weeks scan. Secondly, intra- and interobserver variability of the maxillary gap sign was evaluated for observers R.L. and A.B. in 2 sessions (affected cases vs. 50 normal fetuses in each session) to reduce the bias of different ultrasound manufacturer visualizations (Philips, GE). Thirdly, the palatino-maxillary diameter (PMD) was examined in stored images, DICOM loops and volumes of the midsagittal and parasagittal view of the fetal head and brain at 11<sup>+0</sup>–13<sup>+6</sup> weeks of gestation from 5 fetuses with isolated CLP and 302 consecutively assessed normal controls. The PMD values in fetuses with isolated CLP and normal controls were compared. <b><i>Results:</i></b> Firstly, 5 out of 6 referred pregnancies with isolated CLP were detected prospectively using the midsagittal view for measurement of nuchal translucency due to an abnormal appearance. One out of 6 patients with isolated CLP declined the 11–13 weeks scan. Secondly, intra- and interobserver variability showed no false positive cases; all cases with isolated CLP were identified by both sonographers; however, in 2 cases the maxillary gap sign was doubtful. Therefore, thirdly, we developed the PMD measurement which increased significantly with crown-rump length (CRL) from respective mean values at CRL of 45 mm to 4.66 mm and to 8.95 mm at CRL of 84 mm. In the CLP group, the PMD was below the 5th percentile of the control group in 4 out of 5 (80%) cases. <b><i>Conclusions:</i></b> The midsagittal view for measurement of nuchal translucency shows a high reproducibility regarding abnormal views for maxillary gap sign. In the midsagittal view of the fetal head, face, and brain at 11–13 weeks, the majority of fetuses with isolated CLP have a measurable abnormality in addition, the PMD.