Sex at birth of person

Status: This standard was approved as a departmental standard on October 1, 2021.


Sex at birth refers to sex assigned at birth. Sex at birth is typically assigned based on a person's reproductive system and other physical characteristics.

Sex at birth may also be understood as the sex recorded at a person's birth (for example, what was recorded on their birth certificate).

Person refers to an individual and is the unit of analysis for most social statistics programs.


Sex at birth and gender refer to two different concepts but are interrelated. While sex at birth is primarily understood in terms of physical and biological features such as chromosomes, genitals and hormones, gender is a multidimensional concept that is influenced by several additional factors, including cultural and behavioural norms, and self-identity.

Caution should be exercised when comparing counts for the sex at birth of person variable with counts for the gender of person variable. For most people, their sex at birth corresponds to their gender. However, some people's gender may be different from their sex at birth. For example, in a given population the group of persons of female sex does not necessarily correspond to the group of persons of female gender, although the two groups are generally very similar given the relatively small size of the transgender and non-binary populations.

The variable 'gender of person' is expected to be used by default in most social statistics programs at Statistics Canada in accordance with the Treasury Board of Canada Secretariat's "Policy Direction to Modernize the Government of Canada's Sex and Gender Information Practices" (2018).

The variable 'sex at birth of person' can be used where information on sex at birth is needed, for example, for measuring some demographic and health indicators. It can be used in conjunction with the variable 'gender of person' to estimate the transgender population. These two variables can also be used, together with the variable 'sexual orientation of person', to estimate the gender and sexual diversity populations, which are often represented by the LGBTQ2+ acronym (lesbian, gay, bisexual, transgender, queer, Two-Spirit or another identity of gender or sexual diversity).

Information on sex at birth may be based on self-reported data or reported by proxy depending on the statistical program.

Some people may be reluctant to provide an answer to the question on sex at birth or may give a different answer depending on the context in which it is asked or the order of the questions (for example, whether the question on sex at birth comes before or after the question on gender). The degree of privacy, safety and perceived relevance for collecting this information may impact how a person responds.

Conformity to relevant internationally recognized standards

This standard includes more detailed and specific information than the recommendations for censuses contained in the United Nations' "Principles and Recommendations for Population and Housing Censuses, Revision 3" (2017). The United Nations document does not state the categories in the definition of sex nor does it specify whether sex refers to sex at birth.

The "Conference of European Statisticians Recommendations for the 2020 Censuses of Population and Housing" (2015) recognizes that some countries have started using sex categories in addition to 'male' and 'female'. The option of a third category for sex is provided in the classification variant of sex in the present standard. The Conference of European Statisticians caution that issues related to data collection and residual disclosure should be considered when using a classification with a third category for sex:

It is known that a small proportional error occurs in reporting or coding large response categories (such as 'male' or 'female') but that these can nevertheless be larger than the number of correctly captured responses for a rare category (such as a 'third' sex). Even among the sub-group of particular interest, response patterns may be particularly sensitive to question wording. It is strongly recommended, therefore, that countries should undertake a rigorous testing programme before attempting to collect such information in the census. Furthermore, it should be noted that including such categories in outputs imposes risk to statistical disclosure since the relevant numbers are likely to be very small, particularly when cross-classified with other census variables.

ISO/IEC 5218:2004 standard ''Information technology - Codes for the representation of human sexes'' specifies a uniform representation of human sexes for the interchange of information. It recognizes two sexes (male and female), consistent with the 'Classification of sex at birth' presented in the present standard. Although the ISO/IEC standard provides numeric codes, it states that these codes do not supplant national standards for codes derived from the names of sexes.

Similar to the World Health Organization's "Gender, equity and human rights, Glossary of terms and tools", this standard refers to sex assigned based on physical characteristics. While the World Health Organization indicates that such characteristics are used to define 'male' and 'female', this standard additionally provides a classification variant with three categories ('male', 'female' and 'intersex').

This standard also shares similarities with the definitions of sex at birth published by Statistics New Zealand in the "Statistical standard for gender, sex, and variations of sex characteristics" (2021) and by the Australian Bureau of Statistics in "Standard for Sex, Gender, Variations of Sex Characteristics and Sexual Orientation Variables" (2021).

Statistics New Zealand defines sex at birth as "the sex recorded at a person's birth (for example, what was recorded on their birth certificate)." The Australian Bureau of Statistics also defines it as sex recorded at birth, which "refers to what was determined by sex characteristics observed at birth or infancy." As in the present standard, they provide variant classifications of sex that include a third category labeled 'another term' in New Zealand and 'another term' and 'non-binary sex' in Australia.


Additional information


Relation to previous version

  • Sex at birth of person October 01, 2021 to current

    The name of the concept has been changed from 'sex' to 'sex at birth', and the definitions in the categories of both classifications have been modified.

  • Sex of person January 25, 2018 to September 30, 2021

    This standard updates the definition by specifying that sex refers to sex at birth typically assigned based on a person's reproductive system and other physical characteristics. This standard also provides a classification variant of sex that recognizes the 'intersex' category. Alpha codes are provided for categories in both classifications presented in this standard.

  • Sex of person May 22, 2007 to January 24, 2018

    This was the departmental standard from May 22, 2007 to January 24, 2018.

Date modified: