The three-generation family history is an important element in diagnosis of a genetic condition, or determine the possibility that one may exist in a family. It can guide decisions about genetic testing for the patient and at-risk family members.
Genetic professionals recognize there are a host of definitions for “family”. Furthermore, some individuals may not know their family history for a multitude of reasons including adoption, privacy, estrangement, death, etc.
Creating the family health history includes obtaining relevant medical history of birth family members (first-, second- and sometimes third- degree relatives. The information is documented in written form or by pedigree.
First-degree relatives of patient: parents, children and siblings
Second-degree relatives of patient: maternal / paternal grandparents, aunts and uncles, grandchildren and half-siblings
Third-degree relatives of patient: cousins

Important Family History Information to Collect
Refer to a prenatal genetic counselor if family history includes any of the following:
- Pregnancy loss, still birth, multiple miscarriages or infertility
- Birth defect(s), autism, developmental delay or intellectual disability
- Known chromosomal abnormalities or genetic condition(s)
- Ethnic background associated with a genetic condition
- Consanguinity (mother and father share a common ancestor)
Refer to a pediatric/adult genetic counselor if family history includes any of the following:
- Pregnancy loss, still birth, multiple miscarriages or infertility
- Birth defect(s), autism, developmental delay or intellectual disability, seizures
- Neurological disorders, sudden or early onset progressive vision/hearing loss
- Sudden or early deaths
- Known chromosomal abnormalities or genetic condition(s)
- Ethnic background associated with a genetic condition
- Consanguinity (mother and father share a common ancestor)
Refer to a cancer genetic counselor if the family history includes any of the following:
- Multiple primary cancer diagnoses in the same individual
- Multiple affected family members (spanning >1 generation)
- Early onset cancer
- Known hereditary cancer predisposition syndrome
- Ashkenazi Jewish ancestry