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about congenital anomaly data

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  • For each data source, information about data collection and analytical methods, limitations, the citation and additional resources can be found on the Data Sources and Methods page.

A congenital anomaly, also called a birth defect, is defined as a condition that results from an abnormality of structure, function or metabolism in one or more parts of the body, with the potential to adversely affect health, development or function. The anomaly is present at birth and may be inherited genetically, acquired during gestation, or inflicted during birth.


Original source: Canadian Institute for Health Information (CIHI); Better Outcomes Registry and Network (BORN) Ontario
Distributed by: Canadian Congenital Anomalies Surveillance Network (CCASN), Public Health Agency of Canada (PHAC)
Cite as: Canadian Congenital Anomalies Surveillance System (CCASS), 2011-2015, Public Health Agency of Canada.


Data Collection Methods

  • Historically, the Canadian Congenital Anomalies Surveillance System (CCASS) collected information about anomalies identified through hospitalization in the first year of life. Since babies with congenital anomalies are often hospitalized more than once in their first year, the CCASS attempts to identify all duplicates using sex, date of birth, province, postal code, geocode, mother’s health insurance number (scrambled to protect confidentiality) and medical conditions. Because there are no unique identifiers to ensure positive identification, incomplete records make matching less accurate and result in over-counting the number of cases.
  • From 2001 to 2011, the CCASS was based on identification of congenital anomalies as a result of hospitalization in the first month of life.
  • Starting in 2012, Ontario congenital anomaly (CA) data are submitted to CCASS by BORN Ontario. These data include a set of 16 CCASS national variables with ascertainment up to one year after birth. BORN Ontario ascertain cases from live births, stillbirths and terminations in which a fetal anomaly or CA has been detected in a hospital.
  • Data are based on place of residence and not location of hospital.

Data Analysis Methods

  • Rates and proportions based on counts less than five (5) are suppressed.
  • Ontario residents treated outside of the province are included if data are obtained through the National dataset.
  • Starting in 2012, data provided by PHAC by type of CA by Census Division level of geography are aggregated into five-year groups, (e.g., data for 2009-2013 were available in 2016; data for 2010-2014 were available in 2017; data for 2011-2015 were available in 2018).
  • The total number of births (live births and stillbirths) provided by CCASS is used in the denominator for the calculation of rates of CAs.


  • The total number of live births given by CCASS is different from that of the Office of the Registrar General. This may be due to the inclusion of out-of-province births. Since the numbers and rates are taken from the data as provided by CCASS, these rates may differ from those of other reproductive indicators.
  • Because there are no unique linkable identifiers kept in the database (to protect confidentiality), the process of matching records of the same individual is more difficult, especially when other information is missing. This can result in over-counting the number of cases.
  • Pregnancy terminations which occur as a result of the detection of congenital anomalies through prenatal testing started to be included with the 2012 data from BORN Ontario.
  • Data are influenced by factors that are unrelated to health status such as availability and accessibility of care, and administrative policies and procedures. This may influence comparisons between areas and over time, particularly for less severe congenital anomalies.


  1. Association of Public Health Epidemiologists in Ontario (APHEO). Congenital Anomalies. 2014.
  2. Association of Public Health Epidemiologists in Ontario (APHEO). Canadian Congenital Anomalies Surveillance System (CCASS). 2013.
  3. Health Canada. Perinatal Health Indicators for Canada: A Resource Manual. Ottawa: Minister of Public Works and Government Services Canada, 2000.

Last updated: February 12, 2019

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