Cornelia de Lange syndrome (CdLS) (also referred to as Brachmann-de Lange syndrome) constitutes a multisystem developmental anomaly which is characterized by facial dysmorphism, upper limb deformities, and mental retardation. We report on two subsequent pregnancies with antenatally diagnosed CdLS at 23 and 14 gestational weeks, respectively, of an otherwise healthy gravida. Molecular genetic testing revealed a rare case of gonadal mosaicism of a nonsense NIPBL gene mutation.