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Pregnancy Outcomes

2005

82-224-X


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Overview — Data sources and data quality

Several sources were used in the compilation of pregnancy statistics. These sources are briefly described below. More detailed information on each of the data sources is available by referring to the surveys listed under Selected surveys from Statistics Canada in the Related products section of this publication.

Sources of data

Counts were taken directly from the databases described below. The rates for all years and all outcomes were calculated using the most current population estimates.

Live births and stillbirths

Counts of live births and stillbirths (one of the components of fetal loss) are taken from the Vital Statistics Birth Database and Stillbirth Database, respectively. These databases contain virtually complete counts of all birth and stillbirth events in Canada. This information, which is provided to Statistics Canada by the vital statistics registry in each province and territory, is extracted from the registration documents completed by the parents and medical attendants.

Induced abortions

Counts of induced abortions were taken from the Therapeutic Abortion Survey database which contains information on abortions performed in hospitals and clinics in Canada, as well as abortions performed on Canadian residents in selected American states, for data years prior to 2004.

As of the 1994/1995 data year, Statistics Canada transferred the responsibility of data collection, compilation and processing for the Therapeutic Abortion Survey to the Canadian Institute for Health Information.

Hospitalized cases of miscarriages

Counts of hospitalized cases of miscarriages (another component of fetal loss) were taken from the Hospital Morbidity Data Base (HMDB) which contains data on inpatient hospitalizations in Canada.

In order to maximize coverage of pregnancies not reported elsewhere, counts of hospitalizations with a most responsible diagnosis of ’illegal’ or ’unspecified type of abortion’ were also taken from the HMDB.

As of the 1994/1995 data year, Statistics Canada transferred the responsibility for the HMDB to the Canadian Institute for Health Information.

Source of population estimates

The population counts used to calculate the rates in this product were taken from: Statistics Canada, Estimates of population, by age group and sex, Canada, provinces and territories, annual (CANSIM Table 051-0001). The population counts in CANSIM are updated quarterly. For the date of the download used in this product, please refer to the footnotes in the Pregnancy outcomes table (CANSIM Table 106-9002).

Disclosure control

Before releasing annual induced abortions data to the public, Statistics Canada requests authorization from those provinces and territories that supplied data for three or fewer hospitals or three or fewer clinics. The data from those provinces and territories from which no authorization was received are suppressed; and if there is only one non-authorrization, then the data from another selected province or territory are suppressed to prevent residual disclosure.

As of 1997, cell counts of less than 5 are suppressed for induced abortion data. To prevent residual disclosure, in addition to these cells with counts of less than 5, other selected induced abortion data cells are also suppressed. Before 2005, the corresponding cells for births and fetal loss data were suppressed as well; but, as of 2005, only the corresponding cells for fetal loss data are suppressed to prevent the residual disclosure of suppressed induced abortions data.

Before 2005, to streamline the suppression process, routine suppression was performed on certain age groups within certain provinces and territories for live births, fetal loss, and induced abortion data. Specifically, the age groups ’Under 20’, ’Under 15’ and ’Age 40 and over’ were suppressed for Prince Edward Island, the Yukon Territory, the Northwest Territories and Nunavut. After 2004, this routine suppression was no longer performed.

No other disclosure control is required for birth or fetal loss data, and no disclosure control is required on total pregnancy data.

In 2005, all fetal loss and induced abortion data were suppressed for the Northwest Territories and Nunavut for confidentiality.

Data quality

This section describes the methodology used in the compilation of pregnancy statistics, and highlights data quality issues.

Total pregnancies

The number (count) of pregnancies is calculated by summing counts of live births, induced abortions, and fetal loss. The counts of total pregnancies as well as the counts for the three outcomes of pregnancy are presented by age group and province or territory of residence of the woman experiencing the pregnancy. Rates for total pregnancy and the three outcomes of pregnancy are calculated using the population counts of women for the specified age groups and province and territory of residence.

Pregnancy data are presented according to the calendar year in which the pregnancy terminated and not the year in which conception took place. As a result, there is some under representation of teenage pregnancies because there will be cases of women who became pregnant when they were 19 years old but whose pregnancy terminated when they were 20 years old.

Due to the improvement in age group estimations for abortion data for the data years 1994 to 1997, the total pregnancy counts by age group at the Canada level no longer match any previously produced statistics.

Although Nunavut became a separate territory as of April 1, 1999, not all sources of information (for example, the Hospital Morbidity Data Base (HMDB)) contained enough information to provide complete and separate data for the1999 calendar year for Nunavut. As a result, separate pregnancy data for Nunavut is available as of data year 2000. Prior to 2000, data for Nunavut and the Northwest Territories are combined.

Live births

Counts of live births are not estimates. They are counts of all registered live births tabulated from the vital statistics registration system in existence in the ten provinces and three territories of Canada. Due to legal requirements, registration of live births is considered to be virtually complete.

Induced abortions

One of the limitations of the Therapeutic Abortion Survey is that information on the age of the woman obtaining an abortion is not always reported, especially for abortions performed in clinics. As a result, age group estimations have to be calculated when necessary. In some cases, information on the residence of the woman is also not available, but no estimations have been done for these cases.

Abortions performed in the United States (US) on Canadian residents

For the original statistical releases of the data years 1994 to 2001 US counts were excluded from the age distribution and included only in the counts for ’unknown’ age group in the category ’unknown province of residence’.

In this current product, the US counts are distributed over the age groups within the category ’Unknown province of residence’. (The abortion counts received from the US are aggregated by age group, but no information is supplied on the province or territory of residence.)

As of the 2004 reference year data, reports of Canadian women obtaining induced abortions in the United States are no longer obtained.

Revision of age group estimations for 1994 to 1997

For the 1994 to 1997 data years, a large number of abortions were reported to the Therapeutic Abortion Survey without any information on the age of the woman. When these data were first released, age groups were estimated at the Canada level in order to produce counts and rates by age group for Canadian residents. No estimations were produced at the provincial or territorial level.

Age groups have now been estimated for induced abortions at the provincial and territorial level. As a result of these new estimations, any previously released age group statistics at the Canada level will not match the latest Canada level statistics.

As well, since induced abortion is one of the outcomes included in the calculation of total pregnancy, the counts and rates by age group at the Canada level for total pregnancy will not match previously published statistics.

Data years 1995 to 1997 (unknown residence and unknown age group)

When data years 1995, 1996 and 1997 were originally released, age estimations were not calculated for the counts of clinic abortions where the area of residence was unknown and the age was unknown. Age estimations have now been calculated for these counts, using the known national age distribution for hospital abortions.

Data year 1998

Ontario reported 2,795 clinic abortions with no age group information. The known proportion of Ontario residents who obtained an abortion in hospital was used to estimate the age group of these clinic counts.

British Columbia reported 725 clinic counts with no age group information. The known proportion of British Columbia residents who obtained an abortion in hospital was used to estimate the age group of these clinic counts.

Estimation of teen subgroups (15 to 17 and 18 to 19)

Statistics on the number of teens in the subgroups 15 to 17 and 18 to 19 rely heavily on estimation. This is particularly a problem for clinic abortions where only the broad age group 15 to 19 has been provided or estimated. The calculation of teen subgroups is important for analysis purposes because the experiences of young teens (15 to 17) tend not to be the same as for older teens (18 to 19).

The teen subgroups were estimated using hospital abortion records in which the woman’s age in single years was usually reported. The proportions of teens in each subgroup were calculated, and then these proportions were applied to counts of abortions for which only the age group 15 to 19 was known (clinic abortions).

Fetal loss

Fetal loss includes stillbirths and hospitalized cases of miscarriages.

Stillbirths

Counts of stillbirths (fetal deaths) are not estimates. They are counts of all registered stillbirths tabulated from the vital statistics registration system in existence in the ten provinces and three territories of Canada. Due to legal requirements, registration of stillbirths is considered to be virtually complete.

Stillbirth data are compiled from the Vital Statistics registration system. As of the 1998 data year, stillbirths with a reported underlying cause of death of ’Termination of pregnancy’ are no longer included in the calculation of fetal loss. These cases are assumed to be reported to the Therapeutic Abortion Survey.

Miscarriages

Counts of hospitalized cases of miscarriage, as well as cases of illegal and unspecified abortion are compiled from the Hospital Morbidity Data Base (HMDB). The vast majority of these cases (over 90%) are miscarriages.

There is a recognized significant undercount of miscarriages. Not all women who miscarry require medical attention, and those who do are most often treated in a non-hospital setting such as a physician’s office or an outpatient clinic. Only cases requiring the hospitalization of the woman can be included in the calculation of fetal loss because there is no national data collection system or reporting requirements for miscarriages treated outside of hospital. Estimations in the literature on the percentage of pregnancies that end in miscarriage range from 10% to 90%, depending upon factors such as the age of the woman and the prevailing abortion rate. In this product, during the period 2001 to 2005, hospitalized cases of miscarriage accounted for an annual average of approximately 1.5 % of total pregnancies.

Improvements in pre-natal treatment, changes in health care services and policies, and the increase in the abortion rate are some of the factors that can influence the count and rate of inpatient hospitalizations formiscarriage. In 1974, stillbirths accounted for about 10% of the fetal loss counts. By 2005, stillbirths accounted for about 22% of fetal loss counts, even though the number of stillbirths had actually dropped. The increase in the proportion of stillbirths is due to the decrease in the number of hospitalizations for miscarriage.

The hospital counts extracted from the HMDB are organized by the province or territory of the reporting hospital rather than by the woman’s province or territory of residence. Historically, the province or territory of the hospital has been used as a proxy for the province or territory of residence of the woman. This practice does not pose a significant problem since 94% to 100% of women hospitalized for miscarriage are hospitalized in their province of residence.

In the HMDB, the diagnoses reported for each hospitalization are coded according to the International

Classification of Diseases (ICD), World Health Organization. The 9th revision (ICD-9) was used for the years shown on this product. Although the 10th revision – Canada (ICD-10-CA) has been used in some provinces since 2001, not all provinces have converted to this classification. Selection of hospitalizations to be included in the calculation of fetal loss was based on the most responsible diagnosis having one of the following codes:

ICD-9 codes: 634, Spontaneous abortion; 636, Illegally induced abortion; 637, Unspecified abortion;

ICD-10-CA codes: O03, Spontaneous abortion; O05, Other abortion.

Rates

Rates are calculated by taking the number of events (total pregnancies, live births, induced abortions or fetal loss) in a given period of time and dividing it by the female population at risk during that period of time, and then multiplying the result by 1,000.

’All Ages’ (total) rates

‘All Ages’ (total) rates are calculated for total pregnancies as well as for each outcome of pregnancy. The ‘All Ages’ rates are defined as the number of events per 1,000 women aged 15 to 49.

It is important to note that for the Pregnancy Outcomes product, the rate for the ‘All Ages’ group for Induced Abortions is based on the female population aged 15 to 49. Whereas, in the Induced Abortion Statistics product, the rate for the ‘All Ages’ group is based on the female population 14 to 44 in tables where there are age breakdowns. (In Induced Abortion tables where there are no age breakdowns, the overall rate is based on the female population aged 15 to 44.). As a result, the ‘All Ages’ rate for abortion will be different, depending upon the product this information is from.

Age-specific rates

Age-specific rates are calculated for total pregnancies as well as for each outcome of pregnancy. Age-specific rates are the number of events per 1,000 females of the same age (or age group).

The age groups used in this publication are: Under 20, Under 15, 15 to 19 (plus the subgroups 15 to 17 and 18 to 19), 20 to 24, 25 to 29, 30 to 34, 35 to 39, and 40 years and over.

The rates for the ’Under 20’ age group are based on the female population aged 14 to 19; the rates for the ’Under 15’ age group are based on the female population aged 14 years; and the rates for the ’40 years and over’ age group are based on the female population aged 40 to 44.