The eXtroardinarY Babies Study: Natural History of Health and Neurodevelopment in Infants and Young Children With Sex Chromosome Trisomy

Inclusion Criteria: 1. Prenatal diagnosis of sex chromosome aneuploidy (by cfDNA, chorionic villi sampling, and/or amniocentesis) 2. Postnatal confirmatory karyotype of XXY, XYY, XXX, XXYY, XYYY, XXXY, XXXX, XXXXX, XXXXY, XXXYY, XXYYY, XYYYY (including any mosaicism with \<80% 46,XX or 46,XY cell line) 3. English or Spanish speaking 4. Age 6 weeks to 12 months 30 days on enrollment Exclusion Criteria: 1. Previous diagnosis of a different genetic or metabolic disorder with neurodevelopmental or endocrine involvement 2. Prematurity less than 34 weeks gestational age 3. Complex congenital malformation not previously associated with sex chromosome aneuploidy 4. History of significant neonatal complications (ie intraventricular hemorrhage, meningitis, hypoxic-ischemic encephalopathy) 5. Known complex Central Nervous System (CNS) malformation identified by neuroimaging