EP05.09: Fetal brain abnormalities in Trisomy 21 and neurological outcome: a retrospective cohort study and questionnaire‐based survey

Trisomy 21 (T21), the most frequent autosomal aneuploidy being compatible with life, is the leading cause of intellectual disability. However, neurological impairment in individuals with T21 is heterogeneous and not yet completely understood. This study aimed to investigate brain abnormalities in fetuses with diagnosed T21 and to assess the impact of brain abnormalities on the neurological outcome. MRI and ultrasound data of fetuses with confirmed T21 were assessed retrospectively by experts in fetal ultrasound and MRI. To investigate the neurological outcome, families of included patients were contacted to carry out a questionnaire assessing the neurological development based on selected developmental milestones. 54 fetuses with confirmed T21 were included. 37 (69%) had diagnosed brain abnormalities including abnormal lateral ventricles (n = 20), cerebellar hypoplasia (n = 12), abnormal subarachnoidal fluid spaces (n = 11), hypoplastic vermis cerebelli (n = 7), abnormal corpus callosum (n = 7), malrotation of the hippocampus (n = 4) or abnormal cortical development (n = 3). Of the enrolled patients, 23 (43%) families completed the questionnaire. Children had a mean (±SD) age of 6.4 ± 4.05 years (min. 2; max. 14) at the time of the questionnaire. 17 (74%) families reported that special support is needed in daily life. Children with T21 and prenatally diagnosed brain abnormality (n = 13) reached milestones of gross motor skills (sitting independently, standing without support, walking independently) later compared to children with T21 without any diagnosed brain abnormalities (n = 10; 15.9 months vs. 13.8 months, 27.8 months vs. 21.0 months and 31.5 months vs. 26.0 months, respectively). Milestones of fine motor skills and language skills showed no difference. This study implicates that prenatally diagnosed brain abnormalities in fetuses with confirmed T21 may be associated with delayed gross motor development. Therefore, fetal brain assessment in fetuses with confirmed T21 may improve prenatal counselling.