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Methods

Data source
Live births and stillbirths are from the Vital Statistics Data Base, a virtually complete count of all vital statistics in Canada. This data base contains information collected from the vital statistics registry in each province and territory.

Since 1995, the Canadian Institute for Health Information (CIHI) has collected data on induced abortions (the Therapeutic Abortion Survey), which are forwarded to the Health Statistics Division at Statistics Canada for processing and analysis. Before 1995, Statistics Canada collected these data.

Induced abortion data used in this article include all reported abortions performed on Canadian residents in hospitals and clinics in Canada.

Each province reports counts of all abortions performed in its hospitals. Except for British Columbia and Québec, these provincial reports provide detailed information, such as age, province of residence, gestation period, marital status, and previous induced abortions. British Columbia provides only aggregate counts of abortions by procedure and age group. Québec provides detailed information on some cases and aggregate counts for others.

Detailed abortion clinic data are reported by the provincial health ministries in Ontario and Alberta. Clinic abortions in Québec and British Columbia are reported as aggregate counts by their respective health ministries. British Columbia clinics also report abortion counts directly to CIHI. All other abortion clinics are surveyed separately and report aggregate counts of abortions by the patient.s province of residence.

Since abortion facilities are not available in Prince Edward Island, that province does not report abortions. Data for Prince Edward Island refer to residents who had an abortion outside the province.

Although not all provinces provide detailed information on abortion cases, the count of abortions and the province of residence of the patient are reliably reported, except for some cases in British Columbia and Québec. Based on an analysis of 1992 detailed abortion data for these two provinces, all cases where the province of residence was not provided were considered to be residents of the reporting province.

Miscarriage counts are taken from the Hospital Morbidity Data Base. This data base of hospital separation records from Canadian hospitals provides a count of cases discharged with a diagnosis of spontaneous or other unspecified abortion.

Historical data are from published reports.^5-7

The population counts used to calculate rates were provided by Statistics Canada.s Demography Division. The counts used were July-adjusted population estimates.

All of these data are available for ages 15 to 19, for the province of residence of the women.

American and other international data are from the Alan Guttmacher Institute and include estimated miscarriage numbers.

This article focusses on recent trends in pregnancy outcomes. (See also Teenage pregnancies, 1974 to 1994 in Volume 9, Number 3 of Health Reports.⁷)

Analytical techniques
The number of pregnancies is calculated by summing live births, induced abortions, stillbirths, and known miscarriages. Pregnancy rates, abortion rates and fetal loss rates are calculated using population counts of women aged 15 to 17, 18 to 19, and 15 to 19. The percentages of pregnancies that ended in a live birth, abortion or fetal loss were also calculated.

Limitations
Teenage pregnancy rates in this article may be underestimated because there is no way of knowing the total number of miscarriages. Not all women who miscarry require medical attention, and those who do are frequently treated in outpatient settings and thus are not included in the Hospital Morbidity Data Base (see Estimating miscarriages).

Pregnancies are counted at the time of termination of pregnancy, not conception. Therefore, the few women who became pregnant at age 14, but whose pregnancy did not end until they were 15, are included, but the larger number of 19-year-olds whose pregnancy ended at age 20 are not included.

The patient.s age was not reported for all abortions in all provinces. When age was not reported for abortions in the years 1995 to 1997, the provincial distribution of cases for which age was known was applied. Because Prince Edward Island does not report abortions, and age is known for only a small proportion of Prince Edward Island residents who obtain abortions elsewhere, the Canadian age distribution of abortion recipients was applied to Prince Edward Island residents for whom age was not reported.

The method used to impute ages for data before 1995 may be slightly different. These differences are not substantial enough to change the overall trends.

For live births registered in Newfoundland between 1974 and 1985, vital statistics data did not include the age of the mother. It was assumed that the age distribution of women at the time of birth approximates that of women who had hospital deliveries in the province in a given year.

Abortion data vary in detail by province, and by whether the data are reported for hospitals or clinics. As well, there is a small potential overlap between abortions and stillbirths. Some stillbirths are reported with abortion as the cause of death. It is unclear whether these cases are also reported to the Therapeutic Abortion Survey. It is more likely, however, that abortions are slightly undercounted, since a small number are now performed in physicians. offices and are not currently included in the total abortion count for each province. Nonetheless, these numbers would not have been substantial in the 1995-to-1997 period.

Detailed characteristics of women having abortions, such as marital status, gestation period and previous deliveries, are not reported by all provinces or by all clinics.

Abortions performed on Canadian residents in the United States are reported to a yearly CIHI survey of selected states (Connecticut, Hawaii, Idaho, Maine, Michigan, Minnesota, Montana, New Mexico, New York, North and South Dakota, Oregon, Vermont, and Washington). The number of Canadian residents who obtained abortions in other states is not known. Because abortions performed on Canadian residents in the reporting states are relatively few and decrease each year, they are not included in the calculations for 1995 to 1997. Before 1995, US figures were included in the totals only, but because of the small number, excluding them in the 1995-to-1997 period does not affect trends. Their inclusion would increase the teenage pregnancy rate by only 0.1 pregnancy per 1,000 women aged 15 to 19 in 1995 (0.06 per 1,000 in both 1996 and 1997).