| Term | Definition |
| Fragile X Syndrome (FXS)- | A genetic X linked condition associated with mental retardation caused by a break or weakness in the long arm of the X chromosome. |
| Chorionic villus sampling | procedure done between 10 week gestation and the end of the 1st trimester of pregnancy in which chorionic villi are extracted with a syringe and cultured to find fetal genetic and chromosomal status |
| Phenobarbital | anti-seizure medication. It is not normally recommended for FXS because it increaser hyperactivity |
| EEG | measurement of electrical activity produced by the brain. |
| Pull-to-sit-test | determine muscle tone in the head at approximately 2 months. Baby is pulled by the arms to the sitting position. The head and the arms are observed during the maneuver. The arms should remain partially flexed at the elbow and the head may lag behind the trunk. When the baby is in the sitting position, the head should be able to come to the upright position for at least a few seconds before dropping forward or backward. |
| Hypertonia | muscles are chronically contracted. May notice that child holds his hands in tight fists or that he seems unable to relax certain muscles. And his legs might cross (like scissors) when you pick him up. |
| Gastrostomy tube | a way to feed individuals who are not able to suck or swallow enough for good nutrition. |