APA Dictionary of Psychology

a fetus that has a significant chance of being born with a mental or physical disorder because of known influences from the parents or other family members (e.g., a mother with diabetes or hypertension). The risk of a mental disorder in a child born into a family with no history of mental disorder is relatively small, but the risk may be as much as 50% in certain cases, such as when the disorder is a sex-linked recessive trait inherited from the mother’s side of the family and the parents are related.