NSGC pedigree notation: 2022 standards, symbols, and gender-inclusive updates

Short version. The NSGC (National Society of Genetic Counselors) pedigree standards are the widely accepted convention for drawing clinical pedigrees. Originally published by Bennett and colleagues in 1995 and revised subsequently, most notably in 2008 and 2022, they define symbols for sex, affected status, deceased individuals, pregnancies, carriers, twins, consanguinity, and assisted reproduction. The 2022 update introduced more explicit guidance on gender-inclusive drawing — distinguishing sex assigned at birth from gender identity and updating symbol conventions for transgender, non-binary, and intersex individuals. Clinical pedigree software should follow the current standard to ensure pedigrees are unambiguous across teams and institutions.

A brief history

Before the 1990s, pedigree drawing varied considerably across centres and textbooks, leading to ambiguity in clinical records shared between institutions. Robin Bennett and the Pedigree Standardization Work Group, convened under the auspices of the NSGC, produced the first widely adopted formal standard in 1995. That standard defined a consistent symbol set and placed the conventions on a firm footing for clinical use.

A 2008 update refreshed the symbol set and added clarifications — particularly around assisted reproductive technology, adoption, and pregnancy outcomes, reflecting changes in reproductive medicine. The 2022 update further revised the standard to be explicit about gender-inclusive drawing, recognising that clinical pedigree conventions had historically conflated sex assigned at birth with gender identity in ways that did not serve transgender, non-binary, or intersex patients well.

The core symbol set

The table below summarises the most commonly used NSGC symbols.

Proband and ascertainment

The proband is the individual through whom a family is ascertained for clinical evaluation. They are indicated on the pedigree with an arrow and, by convention, the letter P. For research, the term consultand is sometimes used for the specific individual seeking counselling, who may or may not be the same as the proband.

Generations are labelled with Roman numerals from the top down (I, II, III), and individuals within a generation are numbered left to right with Arabic numerals. A specific individual can therefore be referenced as, for example, III-2.

Consanguinity and assisted reproduction

Consanguineous unions are indicated with a double horizontal line between the two partners. Where the consanguinity is documented, the shared ancestors should be drawn if possible so Wright's coefficient and the inbreeding coefficient F can be calculated; see our consanguinity calculator.

Assisted reproductive technology has specific conventions in the 2008 and 2022 updates. Notation exists for donor gametes (D for sperm donor, O for egg or ovum donor), surrogacy arrangements, and in vitro fertilisation, allowing an accurate biological-vs-social relationship to be recorded. These details matter for genetic risk calculations, which must be based on biological ancestry.

The 2022 gender-inclusive update

The 2022 NSGC update addressed a long-standing tension in clinical pedigree drawing: the square-and-circle convention maps to sex assigned at birth and is used to track inheritance through the X and Y chromosomes, but it had sometimes been applied (incorrectly) as a statement about gender identity. The updated guidance:

• Clarifies that square and circle refer to sex assigned at birth, which is the relevant variable for most genetic inheritance calculations.
• Provides notation for gender identity alongside sex assigned at birth, so a transgender man would be recorded with a circle (sex assigned at birth) and an annotation or modifier indicating male gender identity.
• Recognises non-binary gender identities with the diamond symbol and a gender-identity annotation.
• Handles intersex and differences of sex development explicitly rather than defaulting to a square or circle.
• Addresses family structure for same-gender couples, donor families, and blended biological-and-social relationships.

The updated conventions do not change the biology of inheritance — a transgender man still transmits autosomes and sex chromosomes according to his chromosomal complement — but they ensure the pedigree represents each individual accurately and respectfully. See our gender-inclusive pedigree drawing page for fuller discussion.

Relationship to other standards

NSGC notation sits alongside several related standards:

• ISCN (International System for Human Cytogenomic Nomenclature): the broader cytogenomic standard. NSGC pedigree conventions align with but do not duplicate ISCN's karyotype nomenclature; see our ISCN pedigree symbols page.
• HGNC: for gene symbols used in annotations.
• HPO (Human Phenotype Ontology): for standardised phenotype capture, often paired with pedigrees in phenotype-first rare-disease workflows.
• ICD-10 / OMIM: for disease annotation on the pedigree.

Clinical-grade pedigree software should support the current NSGC symbol set as a default and offer the corresponding annotations in line with ISCN and HGNC.

Common drawing pitfalls

• Ambiguous quadrant shading without an accompanying legend makes multi-condition pedigrees unreadable.
• Missing proband arrow leaves readers guessing at ascertainment.
• Unlabelled pregnancies (live, lost, terminated) lose valuable clinical information.
• Omitted consanguinity line leads to recessive-risk underestimation.
• Conflating sex and gender in the symbol choice, instead of using the symbol for sex assigned at birth and an annotation for gender identity.
• Missing age and year of birth/death — essential for age-dependent penetrance calculations.

How Evagene supports this

Evagene uses the current NSGC standard as its default symbol set, applying symbols automatically based on recorded sex at birth, gender identity, affected status, carrier status, deceased status, pregnancy outcome, and relationship type. The 2022 gender-inclusive conventions are built in: clinicians can record gender identity alongside sex assigned at birth without losing the biologically relevant inheritance information.

Pedigree rendering enforces the notation consistently across individuals, so a pedigree imported from an external GEDCOM or drawn from a live consultation is presented in one uniform style. Consanguinity is drawn with the double-line convention automatically when shared ancestry is detected. Twins bracketing, pregnancy-outcome triangles, adoption brackets, and deceased strike-throughs are all generated from the annotated data rather than requiring manual symbol placement.

Because the notation is enforced by the software rather than the clinician's hand, pedigrees are visually uniform across a service and remain interpretable when shared between institutions. PDF, PNG, and SVG exports preserve the NSGC notation without reformatting, and the embeddable viewer renders the same symbol set in patient portals or EHR integration layers.

Frequently asked questions

Related reading

• ISCN pedigree symbols
• How to draw a pedigree chart
• Gender-inclusive pedigree drawing
• Three-generation family history
• Pedigree drawing software
• Clinical genetics pedigree tools