Square
Represents a man or boy.
Standardised pedigree notation
An illustrated catalogue of the symbols, relationships, annotations and reporting conventions used to build and interpret a clinical pedigree.
This reference implements the standardised human pedigree nomenclature described by Bennett and colleagues in 1995 and 2008, together with the 2022 focused revision concerning gender, sex and carrier representation. Some interface and layout behaviours are software implementation choices and are identified as such.
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Core symbols
The outer shape establishes the individual symbol. Additional marks communicate status, identity and uncertainty.
Circle
Represents a woman or girl.
Diamond
Represents a non-binary or gender-diverse person, or an individual whose gender is unknown, unspecified or not clinically relevant.
Multiple individuals
A number inside a symbol may represent a known number of individuals of the same status.
Number unknown
Use “n” when the number of equivalent individuals is unknown or not specified.
Deceased individual
A diagonal line through the symbol indicates that the individual is deceased.
Unknown clinical status
A question mark inside an otherwise unfilled symbol indicates that affected status is unknown. It does not mean unaffected.
Gender and sex assigned at birth
The 2022 focused revision separates the symbol used for gender identity from annotations used for sex assigned at birth.
Gender identity shapes
Use the square, circle or diamond according to the individual’s gender identity.
AMAB, AFAB and UAAB
Record sex assigned at birth beneath the symbol where it is clinically relevant and appropriate to document.
Do not use nested square-and-circle symbols
The focused revision recommends the symbol corresponding to gender identity, with AMAB, AFAB or UAAB as an annotation where needed.
A diamond without an annotation indicates that gender and sex are unknown, unspecified or not relevant to the clinical question.
Clinical status and fills
Fill patterns represent conditions or states. Their meaning must be defined in the pedigree legend.
Unaffected
An unfilled symbol indicates that the person is unaffected by the condition represented in the legend.
Affected
A fully filled symbol indicates affected status for the defined condition.
Two conditions
Divide the symbol into separately defined regions when two findings must be shown.
Four-condition quadrant fill
Quadrants may encode multiple conditions when each region is clearly mapped in the legend.
Carrier pattern
Use a divided, patterned region for carrier status rather than a central dot.
Affected and carrier
Use distinct regions or patterns so that one state does not obscure another.
Presymptomatic or asymptomatic carrier
Use a legend-defined patterned region and supporting annotation when an individual carries a dominant-condition variant but has no current manifestations.
Legacy convention. A central dot was historically used for carrier status. The 2022 focused revision recommends divided, patterned fills instead.
Proband and consultand
The proband and the consultand may be the same person, but they are not interchangeable concepts.
Proband
An arrow identifies the affected individual through whom the family came to attention for the condition under study.
Consultand
A “P” identifies the person receiving genetic counselling or evaluation when distinct from the proband.
Relationships
Relationship lines describe family structure. They should remain distinct from biological and adoptive lines of descent.
Current relationship
A solid horizontal line joins partners.
Relationship no longer exists
A slash through the relationship line indicates that the relationship has ended.
Multiple partners
Show separate relationship lines where they affect genetic assessment or offspring structure.
Consanguinity
A double relationship line indicates a consanguineous union. State the degree when it is not obvious from the pedigree.
No children
Use a terminal mark and annotate whether this is by choice or for an unknown reason.
Infertility
Annotate infertility and its known reason beneath the relationship line.
Single-parent descent
A descent line may begin from one recorded parent when the other biological parent is not represented.
Children and sibships
Descent and sibship lines encode parent-child structure and sibling order.
Descent and sibship lines
A vertical descent line connects the parental relationship line to a horizontal sibship line.
Birth order
List siblings from oldest to youngest, left to right.
Half-siblings
Children from different parental relationships must connect to their corresponding union.
Generation and individual identifiers
Use Roman numerals for generations and number individuals from left to right within each generation.
Twins and multiple births
Multiple births branch from a common apex. Zygosity is communicated by an additional connecting line or annotation.
Dizygotic twins
Two branches originate from the same point without a connecting bar.
Monozygotic twins
A connecting line between the twin branches indicates monozygosity.
Unknown zygosity
Use a question mark where zygosity is unknown.
Triplets
Three branches originate from one apex. Add zygosity marks where known.
Pregnancy outcomes
Record gestational age where known and define affected fills in the legend.
Ongoing pregnancy
Use a pregnancy symbol with “P” and gestational age.
Fetal sex known
Annotate AMAB or AFAB and document how fetal sex was determined where relevant.
Spontaneous abortion
Use the reproductive-loss symbol and annotate gestational age.
Affected spontaneous abortion
Fill the symbol and define the affected condition in the legend.
Ectopic pregnancy
Use the pregnancy-loss symbol annotated “ECT”.
Termination of pregnancy
Use a pregnancy-loss symbol with a diagonal slash and annotate the indication where known.
Stillbirth
Use the appropriate individual symbol with a diagonal death mark, “SB” and gestational age.
Gestational-age annotation
Place the known gestational age beneath the symbol.
Adoption
Brackets identify adopted individuals. Biological and adoptive relationships remain visually distinct.
Adopted into family
Use brackets around the individual and a dashed line from adoptive parents.
Adopted out
Use brackets and preserve the solid biological descent line.
Biological and adoptive descent
Solid lines indicate biological descent; dashed lines indicate adoptive descent.
Adopted by a relative
Show both the biological and adoptive family structures where clinically relevant.
Assisted reproduction
These are relationship scenarios, not isolated icons. Available donor and gestational-carrier history should be recorded where relevant.
Sperm donor
Mark the donor with “D”. Do not draw a partner relationship line between the donor and the person carrying the pregnancy.
Ovum donor
Represent the donor contribution separately from the gestational parent and partner relationship.
Embryo donation
Show both gamete donors and the gestational parent without implying a partner relationship with the donors.
Gestational carrier
Mark the gestational carrier with “S” and connect the pregnancy to the person carrying it.
Donor who is also the gestational carrier
Use the donor designation and place the pregnancy beneath the person carrying it.
Double-gamete donation
Show both donors and connect the pregnancy to the gestational parent.
Annotations and identifiers
Keep annotations concise, consistently ordered and proportionate to the clinical purpose.
Recommended order
Age or birth/death year, evaluation result, then pedigree identifier.
Pedigree identifiers
Use identifiers such as I-1, II-3 and III-2 in research, publication and cross-reference contexts.
Clinical reporting requirements
A clinical pedigree is part of the health record. Record enough context for another clinician to understand how and why it was created.
- Name of the proband or consultand
- Family names or initials where appropriate
- Name and title of the person recording the pedigree
- Historian who supplied the family history
- Date of intake or update
- Indication for taking the pedigree
- Clinically relevant ancestry
- Legend defining every fill and pattern
- Known ages, diagnoses and ages at onset
- Known ages and causes of death
- Relevant test or evaluation results
- Confidentiality-conscious identifiers
Layout and line routing
The standards define the visual relationships. The application’s coordinate and routing model is an implementation choice designed to preserve them during editing.
Clinical routing
Uses horizontal relationship and sibship lines with vertical descent and child branches.
Flexible routing
Maintains connectivity during free manual movement but may introduce diagonal segments.
Coordinate model
_cx stores the automatic horizontal position, _gen the generation, x/y the rendered coordinates, and px/py manually pinned coordinates.
Complete pedigree examples
These worked diagrams combine the atomic rules into recognisable clinical scenarios.
Three-generation rare-disease pedigree
Demonstrates: three generations, proband, affected status and sibling order.
Conventions: standard symbols, orthogonal descent, Roman generation numbering.
Common mistake: collecting only the parents and siblings of the proband.
Autosomal dominant family
Demonstrates: affected individuals in successive generations.
Conventions: affected fill and vertical transmission.
Common mistake: inferring inheritance solely from a small pedigree.
Autosomal recessive consanguineous family
Demonstrates: unaffected parents, affected siblings and consanguinity.
Conventions: double relationship line and carrier patterns.
Common mistake: omitting the degree of relationship when it is not visually obvious.
X-linked family
Demonstrates: affected males and a carrier mother.
Conventions: patterned carrier region and no male-to-male transmission.
Common mistake: using a central carrier dot without a legend.
Hereditary cancer pedigree
Demonstrates: multiple affected relatives and age-at-diagnosis annotations.
Conventions: condition-defined fill and concise clinical labels.
Common mistake: recording cancer type without age at diagnosis.
Prenatal family with pregnancy outcomes
Demonstrates: ongoing pregnancy, spontaneous abortion and gestational age.
Conventions: distinct pregnancy-outcome symbols.
Common mistake: recording all losses as an undifferentiated “no living child”.
Adoption scenario
Demonstrates: biological and adoptive parentage.
Conventions: brackets, solid biological descent and dashed adoptive descent.
Common mistake: showing only the rearing family when biological history is clinically relevant.
Assisted-reproduction scenario
Demonstrates: donor gamete and gestational parent.
Conventions: donor “D”, carrier “S” and no implied partner relationship with donors.
Common mistake: conflating genetic contribution, gestation and parenting.
Gender-inclusive clinical pedigree
Demonstrates: gender-identity symbol with sex-assigned-at-birth annotation.
Conventions: square, circle or diamond plus AMAB, AFAB or UAAB where appropriate.
Common mistake: using nested square-and-circle symbols.
Multiple-condition fill and legend
Demonstrates: affected status plus a separate carrier finding.
Conventions: divided regions and an explicit legend.
Common mistake: using patterns without defining them.
References
The 2022 publication is a focused revision and retains the underlying 2008 recommendations except where specifically revised.
Bennett RL, Steinhaus KA, Uhrich SB, et al. Recommendations for standardized human pedigree nomenclature. American Journal of Human Genetics. 1995;56:745–752. https://doi.org/10.1007/BF01408073
Bennett RL, French KS, Resta RG, Doyle DL. Standardized Human Pedigree Nomenclature: Update and Assessment of the Recommendations of the National Society of Genetic Counselors. Journal of Genetic Counseling. 2008;17:424–433. https://doi.org/10.1007/s10897-008-9169-9
Bennett RL, French KS, Resta RG, Austin J. Practice resource-focused revision: Standardized pedigree nomenclature update centered on sex and gender inclusivity. Journal of Genetic Counseling. 2022;31:1238–1248. https://doi.org/10.1002/jgc4.1621
