There are four primary categories of causes of developmental disabilities:
- Chromosomal and genetic
- Toxic and infectious substances intrauterine
- Other types of high-risk pregnancies
- Post-natal causes.
- The most common cause of disability in this category is Down Syndrome, but there are over 2000 identified genetic disorders that cause mental retardation. Two of the best-known are Fragile X and phenylketonuria (PKU). There is no known method of preventing disabilities due to chromosomal and genetic causes. Some conditions can be detected in the fetus. PKU is treatable if the proper test is conducted immediately following birth and the diet is properly restricted if the condition is found to exist.
- During pregnancy, women should be especially careful of using substances know to be harmful. Almost any amount of alcohol usage, for example, can cause damage to a fetus. Smoking is also strongly discouraged during pregnancy, as is the use of any illegal substance. Use of cocaine results in babies with low birth weight, seizures, and physical malformations. Infants of adults addicted to heroin may go through severe withdrawal symptoms at birth, causing either brain damage or death. Even routine radiation (e.g. for dental x-rays) should be avoided if possible.
- Any kind of birth that reduces oxygen to the baby's brain can be extremely harmful. Pregnant mothers should be certain to eat properly, especially during the third trimester when fetal brain tissue is developing rapidly. Vitamin and mineral deficiencies (e.g. folic acid) can result in neural tube defects.
- Post-natal causes include vehicle accidents, near-drowning, severe child abuse and neglect, lead poisoning and iron deficiency. Special care should be taken to avoid lead poisoning in sub-standard housing, in which babies may be exposed to lead-based flaking paint.