- Chromosomal disabilities such as Down Syndrome, Mosaic Trisomy 16, Fragile X, Klinefelter Syndrome (XXY), Cri-du-chat Syndrome, Angelman Syndrome, etc.
- Some endocrine abnormalities such as Prader Willi, Cushing’s Syndrome, hypothyroidism, PKU, for example. More than 3,000 different congenital abnormalities are known.
- Infections (Rubella, CMV)
- Poor maternal nutrition
- Alcohol/drug use: Fetal Alcohol Syndrome/Spectrum Disorder (FAS, FASD)
- Errors in development such as: Spina bifida, cleft palate, microcencephaly, macroencephaly, other neural-tube defects (may be caused or complicated by folic acid deficiency, undiagnosed diabetes, and/or unknown environmental exposures);
- Autism (maybe)
- Oxygen deprivation related brain damage
- Brain injury from forceps/difficult deliveries (Cerebral Palsy, seizure disorders, etc)
Postnatal (after birth)
- Shaken Baby Syndrome
- Head or Traumatic Brain Injury
- Lead, mercury, alcohol, other poisoning
- Huffing of chemical inhalants, paint, glue, etc. (by children under age 22)
- Autism Spectrum Disorder & other Pervasive Developmental Disorders
- Other neurological issues such as Tourette Syndrome, ADHD, and early dementia which are not well understood may sometimes be associated with people in I/DD services, but are not considered to be developmental disabilities alone.