Maternal hypertension in Canada

Summary

  • In 2010/11, the rate of gestational hypertension without proteinuria in Canada was 46.3 (95% CI: 45.4-47.0) per 1,000 deliveries. The overall rates of gestational hypertension without proteinuria increased between 2004/05 and 2010/11 (Table 1 and Figure 1).
  • Over the seven-year time period (2004/05–2010/11), the rates of pre-existing hypertension and pre-eclampsia remained relatively stable (Table 1 and Figure 1). Rates of eclampsia have decreased.
  • Differences in the rates of gestational hypertension were observed across age groups. Higher rates were observed among women 40 years and older (Figure 2).
  • The overall rates of gestational hypertension varied across provinces and territories. The rates were highest in Newfoundland and lowest in the Northwest Territories (Table 2).

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Organization:
Type: Fact Sheet
Date published: 2014-10-09
 
Table 1: Temporal trends rate (per 1,000 deliveries) in maternal hypertension in Canada, 2004/05–2010/11
Type of hypertension 2004/2005 2005/2006 2006/2007 2007/2008 2008/2009 2009/2010 2010/2011
Pre-existing hypertension 4.6 4.8 5.1 5.2 4.9 5.1 5.1
Gestational hypertension without proteinuria 45.0 45.4 44.9 44.5 45.5 46.3 46.2
Pre-eclampsia 11.9 12.1 12.1 12.3 12.0 12.4 11.5
Eclampsia 1.5 1.3 0.9 0.7 0.8 0.8 0.8

Source: Canadian Institute for Health Information, Discharge Abstract Database (DAD). Quebec data was not included because it does not contribute to DAD

 

Figure 1: Rates (per 1,000 deliveries) of hypertension among pregnant women in Canada, 2004/05–2010/11

Line graph - Rates (per 1,000 deliveries) of hypertension among pregnant women in Canada, 2004/05–2010/11. See Table 1 for text description.

Source: Canadian Institute for Health Information, Discharge Abstract Database (DAD). Quebec data was not included because it does not contribute to DAD

 

Figure 2: Rate (per 1,000 deliveries) of gestational hypertension (without proteinuria) by age group in Canada, 2004/05–2010/11

Bar graph - Rate (per 1,000 deliveries) of gestational hypertension (without proteinuria) by age group in Canada, 2004/05–2010/11. Text description follows.

Source: Canadian Institute for Health Information, Discharge Abstract Database (DAD). Quebec data was not included because it does not contribute to DAD

Description - Figure 2
Table - Rate (per 1,000 deliveries) of gestational hypertension (without proteinuria) by age group in Canada, 2004/05–2010/11
Age group 2004/05 2005/06 2006/07 2007/08 2008/09 2009/10 2010/11
15-19 years 41.49 38.72 43.21 40.53 38.65 39.78 42.51
20-24 years 42.69 44.46 42.42 40.30 43.93 42.20 41.56
25-29 years 45.70 46.36 45.19 45.73 44.83 46.28 44.98
30-34 years 43.35 43.12 43.51 42.66 44.45 44.79 44.77
35-39 years 47.41 48.71 47.36 47.26 49.13 50.76 52.54
40-44 years 61.54 59.20 57.88 63.93 59.73 65.64 64.54
45-49 years 75.41 74.19 76.70 100.00 86.33 106.47 92.72
 
Table 2: Rates of gestational hypertension (without proteinuria) by province and territory in Canada, 2004/05–2010/11
Province/Territory Rate per 1,000 deliveries 95% CI
Newfoundland and Labrador 68.8 66.0–71.7
Prince Edward Island 59.3 54.5–64.4
Nova Scotia 60.5 58.6–62.5
New Brunswick 47.4 45.5–49.3
Ontario 42.1 41.7–42.5
Manitoba 54.1 52.7–55.5
Saskatchewan 48.0 46.6–49.5
Alberta 50.7 49.9–51.4
British Columbia 40.3 39.6–41.1
Yukon 40.8 33.2–49.7
Northwest Territories 32.9 28.3–38.0
Nunavut 54.9 46.3–64.6
Canada 45.4 45.1–45.7

Source: Canadian Institute for Health Information, Discharge Abstract Database (DAD). Quebec data was not included because it does not contribute to DAD

CI: confidence interval

 

Definition

Hypertension in pregnancy is defined as a diastolic BP of ≥90 mmHg and is classified as pre-existing or gestational. Pre-existing hypertension pre-dates pregnancy or appears before 20 weeks, and gestational hypertension appears at or after 20 weeks. Pre-eclampsia is characterized by high blood pressure and significant amounts of protein in the urine in a pregnant woman (≥0.3g/d in a 24-hour urine collection or ≥30 mg/mmol urinary creatinine in a spot urine sample). Eclampsia is characterized as seizures (convulsions) in a pregnant woman that are not related to a pre-existing brain condition. Rates are expressed per 1,000 deliveries in a given place and time.

Data source

Rates of maternal hypertension were calculated using data from the Discharge Abstract Database (DAD) of the Canadian Institute for Health Information for the period 2004/10–2010/11. This database contains information on all hospital discharges in Canada (except Quebec). Diagnoses and procedures in the database are coded using the International Statistical Classification of Diseases, Tenth Revision (ICD-10CA).

The rates are calculated based on fiscal years (i.e., April 1 to March 31).

Limitations

Our data may underestimate the actual rates of maternal hypertension in Canada, as all maternal hypertension could not be identified due to limitations of the ICD-10CA codes (i.e. miscoding, unspecified hypertension). Maternal hypertension rates in Quebec could not be estimated because this province’s data were not part of the Discharge Abstract Database (DAD). Case ascertainment was limited to the province/territory of occurrence; therefore the data may therefore not accurately reflect the regional differences in Canada.

 
The Public Health Agency of Canada’s Canadian Perinatal Surveillance System monitors and reports on key indicators of maternal, fetal and infant health in Canada. For more information visit: Canadian Perinatal Surveillance System (CPSS)
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