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39–HLT Low birth weight
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Definition
Rationale and notes for interpretation
Technical specifications
Data availability
Considerations for indicator quality and comparability
Responsibility to produce the data
Definition
The proportion of live births (birth weight known) with a birth weight less than 2500 grams and at least 500 grams.
Rationale and Notes for Interpretation
Low birth weight is an indicator of the general health of newborns, and a key determinant of infant survival, health and development. Low birth weight infants are at a greater risk of dying during the first year of life, and if they survive, they have a greater risk of disability and diseases such as cerebral palsy, visual problems, learning disabilities and respiratory problems. Low birth weight is associated with multiple births (twins, triplets, etc.), pre-term births, poor maternal health, lifestyle and economic circumstances. It is also associated with assisted conception (and related multiple births).
Appropriate medical care and a healthy lifestyle for the mother can improve the chances that the baby will have a healthy birth weight. It should be noted that a potentially confounding factor is variations in the ethnic composition of the population since some ethnic groups tend to have babies of lower weight, even though these infants are otherwise healthy.
The low birth weight rate in 1997 for 26 of 30 developed countries was 6.1% of live births, compared with 5.8% in Canada (OECD). Among developed countries, a low birth weight rate of less than 5.0 is considered good.
Over time, there has been improved reporting of live births <500 grams; to improve comparability over time in reporting on low birth weight, births under 500 grams are excluded. Births with unknown birth weights are also excluded from the calculation.
There are some concerns with comparability of this indicator in specific jurisdictions due to missing birth registrations or data quality problems. Historic problems have been identified. Any problems with comparability in later years will be noted with the release of these data.
Technical Specifications
Exclusions: Births with unknown birth weight; births to mothers not resident in Canada are excluded from the numerator and denominator; infants born outside the province/territory of residence of their mothers are included in the rates for the mother’s province/territory of residence.
Calculation: Low birth weight percentage = (numerator/denominator) x 100
- births are assigned to jurisdiction by mother’s P/T of residence.
- no adjustment for age of mother.
Numerator:
- Number of live births < 2500 grams within the specified year.
- Number of live births ≥500 and <2500 grams within the specified year.
Denominator:
- Total live births within the specified year.
- Total live births with known birth weight ≥ 500 grams within the specified year.
Source: Statistics Canada, Vital Statistics, Birth database; ISQ.
References: Statistics Canada Catalogue 84F0210XPB, Births and Deaths; Community Health Indicators – Definitions and Methods, CIHI, 1995; Statistical Report on the Health of Canadians, ACPH, 1999; Stat Can web site.
Data Availability
- Low birth weight results are reported as a percent, with one decimal place.
- Results from the most recent year (2005) are reported.
- Over 20 years of data (1979 to 2005) available on a consistent basis for Canada, the provinces (except for Newfoundland, for which birth weight is only available from 1991) and the territories.
Considerations for Indicator Quality and Comparability
No known issues.
Responsibility to Produce the Data
Statistics Canada
