OP25.04: The retronasal triangle view and maxillary gap at 11–13 weeks in the detection of cleft lip and palate with or without secondary palate involvement

To evaluate the presence of a “maxillary gap” and/or an abnormal retronasal triangle view in the first trimester fetuses with cleft lip and palate (CLP) or with cleft palate only (CP). The retronasal triangle view and the mid sagittal view of the fetal face at 11–13 weeks were retrospectively examined in 18 fetuses later diagnosed with CLP, 1 with CP only and 19 normal controls to assess if an abnormal retronasal triangle view and/or a “maxillary gap” were present. Cases with isolated cleft lip were not included in the study. The neonatal outcome was confirmed after birth or, in cases of termination of pregnancy, at postmortem examination. The interobserver variability was also investigated. The study population included 11 bilateral, 4 unilateral, 3 median CLP and 1CP. Eight out of bilateral (72%), 2 out of unilateral (50%) and 2 out of median (66%) CLP and 1 CP had a secondary palate defect. In the remaining cases an upper alveolar ridge defect was present. An abnormal karyotype was less associated with unilateral CLP. In 7 cases of CLP and in 1 CP (42%) there were also additional fetal defects. A maxillary gap was observed in 11/13 cases with a secondary palate defect, in 0/6 cases with an upper alveolar ridge defect only and in 3/19 normal cases. An abnormal retronasal triangle view was reported in 16/19 abnormal cases and in 4/19 normal controls. The interobserver variability was not significant for both signs. The “maxillary gap” sign is more sensitive to detect CLP with a secondary palate defect, whereas the retronasal triangle view allows to visualise the upper alveolar ridge defect. Both in combination show to be a helpful tool in the detection of facial clefts at 11 to 13 weeks of gestation.