First-Trimester Bilateral Choanal Atresia as a Marker of a De Novo Pathogenic KMT2D Variant Associated With BCAHH Syndrome.

What is already known about the topic? ◦. Prenatal detection of choanal atresia is uncommon and, to our knowledge, has not been reported in the first trimester. ◦. Similarly, antenatal identification of the recently described BCAHH syndrome has not been previously reported. What does this study add? ◦. This study provides the first description of a first‐trimester sonographic appearance suggestive of choanal atresia, enabling the first reported prenatal diagnosis of BCAHH syndrome, a rare and severe condition caused by a pathogenic KMT2D gene variant. ◦. It demonstrates the feasibility of ultrasound detection of choanal atresia and may aid in the prenatal recognition of this malformation and associated syndromic conditions.