Health Fact Sheets
Preterm births among mothers from racialized groups, 2016-2021
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Summary
Data from the mother-centric data linkages show that:
- In Canada, the proportions of single births (i.e., singleton births) that were preterm (<37 weeks) were higher among South Asian (6.9%) and Black mothers (6.3%) compared with non-racialized, non-Indigenous mothers (5.5%).
- All racialized groups of mothers had higher proportions of extremely and very preterm singleton births (<32 weeks) compared with non-racialized, non-Indigenous mothers.
- The proportion of preterm multiple births was more common among South Asian mothers than among non-racialized, non-Indigenous mothers (69.2% vs 58.2%).
- Compared with mothers aged 25-34, proportions of singleton preterm births were higher for mothers aged 35-39 and 40+ among all racialized groups and non-racialized, non-Indigenous mothers, whereas for mothers under 25, the increase was observed only in non-racialized, non-Indigenous mothers.
Background
Preterm infants are born before 37 weeks of gestation, often before the major stages of brain, lung, and immune system maturation are complete. They face higher chances of illness, disability, hospitalization and death.Note 1 Families may also experience significant financial and emotional stress.Note 2
Most preterm births occur spontaneously but some are provider-initiated, when early delivery is recommended for the safety of the mother or baby. Common causes of preterm births include multiple pregnancies, infections or chronic conditions.Note 3
Canada’s preterm birth rate has risen over time, from 6.5% in 1991 to 8.0% in 2021. During this period, preterm birth rates increased modestly by 0.7% among single births (i.e., singleton births) but rose sharply by 19% among multiple births.Note 4 In 2021, extremely (less than 28 weeks of gestation) and very preterm infants (28 to less than 32 weeks of gestation) represented around 1% of total live births in Canada, while moderate to late preterm infants (32 to less than 37 weeks of gestation) accounted for 6.9%.Note 5
Canada’s population is diverse. In 2021, South Asian, Chinese, and Black populations together accounted for over 16% of the total population.Note 6 Limited information exists on how preterm births vary across racialized groups, though studies based on older cohorts of Canadian mothers show higher singleton preterm birth rates among some groups (e.g., South Asian and Black women).Note 7
As Canada’s population grows more diverse and the rate of multiple births increases, it is becoming increasingly important to monitor preterm births according to maternal race.Note 8
This Health Fact Sheet provides estimates of:
- preterm birth rate of singleton and multiple births among mothers from the three most common racialized groups and
- the singleton preterm birth rate disaggregated by maternal age and by maternal race.
Single preterm births were more common among South Asian and Black mothers than among non-racialized, non-Indigenous mothers
In Canada, the proportion of singleton preterm births (<37 weeks) varied across racialized groups for the combined years of 2016 to 2021 (Chart 1). For singleton births, the proportion of preterm births was higher among South Asian mothers (6.9%) and Black mothers (6.3%) than among non-racialized, non-Indigenous mothers (5.5%).
Data table for Chart 1
| Racialized group | Less than 37 weeks | ||
|---|---|---|---|
| Proportion | 95% confidence interval | ||
| Lower | Upper | ||
| percent | |||
| Note: Non-racialized, non-Indigenous mothers are the reference group.
Source: Mother-centric data linkages, 2023 |
|||
| Non-racialized, non-Indigenous | 5.5 | 5.4 | 5.6 |
| South Asian | 6.9 | 6.7 | 7.2 |
| Chinese | 5.5 | 5.2 | 5.9 |
| Black | 6.3 | 6.0 | 6.6 |
| Other racialized groups | 6.5 | 6.3 | 6.7 |
All racialized groups of mothers had higher proportions of extremely and very preterm single births than non- racialized, non-Indigenous mothers
In Canada, for the combined years of 2016 to 2021, most singleton pregnancies were carried to term (>93%), a pattern consistent for all groups. Extremely and very preterm births (<32 weeks) were rare, representing less than 1% of live singleton births for most groups (Chart 2).
All racialized maternal groups had higher proportions of extremely and very preterm births (<32 weeks), compared to non-racialized, non-Indigenous mothers. Black mothers had the highest proportion (1.5%) of extremely and very preterm singleton births.
Data table for Chart 2
| Racialized groups | Less than 32 weeks | 32 - 36 weeks |
|---|---|---|
| percent | ||
| Source: Mother-centric data linkages, 2023 | ||
| Non-racialized, non-Indigenous | 0.6 | 4.9 |
| South Asian | 0.9 | 6.0 |
| Chinese | 0.8 | 4.7 |
| Black | 1.5 | 4.8 |
| Other racialized groups | 0.9 | 5.6 |
Among multiple births, over half were born preterm across all groups
A multiple birth is defined as twins, triplets, or more. Twins represent the largest category of multiple births (97%).Note 9 In Canada, from 2016 to 2021, the proportion of multiple births among all live births was approximately 3%.Note 4 The most common complication of multiple gestations is preterm birth.Note 10
Fewer than 50% of multiple gestations were carried to term (Chart 3). This pattern was consistent across groups. For all groups, moderate to late preterm births (32-36 weeks) were more common than extremely and very preterm births (<32 weeks).
The proportion of overall preterm births (<37 weeks) was higher among multiples born to South Asian mothers (69.2%), compared to those born to mothers who were non-racialized, non-Indigenous (58.2%). The proportions of extremely and very preterm births (<32 weeks) were similar across groups, ranging from 7.2% to 9.3%.
Data table for Chart 3
| Racialized groups | Less than 32 weeks | 32-36 weeks | Less than 37 weeks (overall preterm) | Full-term | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Proportion | 95% confidence interval | Proportion | 95% confidence interval | Proportion | 95% confidence interval | Proportion | 95% confidence interval | |||||
| Lower | Upper | Lower | Upper | Lower | Upper | Lower | Upper | |||||
| percent | ||||||||||||
| Source: Mother-centric data linkages, 2023 | ||||||||||||
| Non-racialized, non-Indigenous | 7.4 | 6.8 | 8.0 | 50.8 | 49.7 | 51.9 | 58.2 | 57.1 | 59.3 | 41.8 | 40.7 | 42.9 |
| South Asian | 9.3 | 7.6 | 11.3 | 59.9 | 56.8 | 62.9 | 69.2 | 66.3 | 72.1 | 30.8 | 27.9 | 33.7 |
| Chinese | 7.2 | 4.9 | 10.3 | 52.8 | 47.7 | 57.8 | 60.0 | 55.0 | 64.9 | 40.0 | 35.1 | 45.0 |
| Black | 7.9 | 6.2 | 10.0 | 45.4 | 41.9 | 48.9 | 53.3 | 49.8 | 56.8 | 46.7 | 43.2 | 50.2 |
| Other racialized groups | 8.3 | 6.8 | 9.9 | 51.8 | 49.0 | 54.6 | 60.0 | 57.2 | 62.8 | 40.0 | 37.2 | 42.8 |
In all racialized and non-racialized maternal groups, the proportion of single preterm births was higher among mothers aged 35-39 and 40+ years than among those aged 25-34 years
Maternal age under 20 and over 35 are associated with higher risk for preterm birth.Note 11 Across all groups, the proportion of singleton preterm births increased from ages 25-34 to 35-39 but further increases in the 40+ group were not observed in all groups. Compared with mothers aged 25-34, a higher proportion of singleton preterm births among mothers younger than 25 was only observed in non-racialized, non-Indigenous mothers.
Compared to non-racialized, non-Indigenous mothers, South Asian mothers had higher proportions of singleton preterm births across all age groups except for those under 25 years. The difference in singleton preterm birth proportions between South Asian and non-racialized, non-Indigenous mothers was greatest in the 40+ age group (11.5% vs 7.9%).
Black mothers aged 25-34 and 35-39 had higher proportions of singleton preterm births than non-racialized, non-Indigenous mothers. The difference in singleton preterm birth proportions between Black and non-racialized, non-Indigenous mothers was greatest in the 35-39 age group (7.3% vs 5.7%).
Singleton preterm birth proportions among Chinese mothers were comparable to those of non-racialized, non-Indigenous mothers across all maternal age groups.
Data table for Chart 4
| Racialized groups | Less than 25 years | 25-34 years | 35-39 years | 40 years and over | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Proportion | 95% confidence interval | Proportion | 95% confidence interval | Proportion | 95% confidence interval | Proportion | 95% confidence interval | |||||
| Lower | Upper | Lower | Upper | Lower | Upper | Lower | Upper | |||||
| percent | ||||||||||||
| Source: Mother-centric data linkages, 2023 | ||||||||||||
| Non-racialized, non-Indigenous | 6.5 | 6.2 | 6.8 | 5.2 | 5.1 | 5.3 | 5.7 | 5.5 | 5.9 | 7.9 | 7.3 | 8.5 |
| South Asian | 5.6 | 4.5 | 6.8 | 6.3 | 6.0 | 6.7 | 8.6 | 7.9 | 9.3 | 11.5 | 9.7 | 13.5 |
| Chinese | 5.7 | 3.7 | 8.4 | 4.9 | 4.5 | 5.3 | 6.5 | 5.8 | 7.3 | 7.5 | 6.0 | 9.2 |
| Black | 5.9 | 5.0 | 7.0 | 5.8 | 5.4 | 6.2 | 7.3 | 6.6 | 8.0 | 7.8 | 6.6 | 9.2 |
| Other racialized groups | 6.2 | 5.4 | 7.1 | 5.8 | 5.6 | 6.1 | 6.8 | 6.4 | 7.3 | 10.3 | 9.3 | 11.3 |
About Preterm Births
A preterm birth is defined as any birth occurring before 37 completed weeks of gestation. This is further categorized into extremely preterm (less than 28 weeks), very preterm (28 to less than 32 weeks), and moderate to late preterm (32 to less than 37 weeks).
Data
The mother-centric data linkage linked the Canadian Vital Statistics —birth data (2016-2021) to the 2021 long-form Census of the Population. Yukon birth data were not available from 2017 to 2021. As a result, national estimates from this analysis excluded Yukon.
The long-form Census questionnaire involved a random sample of one in four private dwellings in Canada to collect detailed sociodemographic or socio-economic information. Since the institutionalized population was excluded from the census and was not part of the mother-centric data linkage, national estimates of preterm births differed slightly from other published source.
The 2021 census weights and replicate weights were applied to birth-census linked data and were not adjusted for missed linkages, as the linkage rate to the Derived Record Depository (DRD) at Statistics Canada was high. The linkage rate of birth mothers to the DRD including the period covered during this study was 94.1%, while the linkage rate for the 2021 Census of Population to the DRD was 96.8%.Notes
This analysis includes live births from the five-year period preceding the 2021 census day (May 11, 2016 - May 11, 2021). Live births with a missing gestational age or with a birthweight of less than 500 grams were excluded. Birthweight less than 500 grams were excluded because linkage rate was consistently lower among immigrant mothers than Canadian-born mothers from 2016 to 2021. This could impact estimates of preterm births among mothers from racialized group as immigrant population account for a large fraction of racialized groups.Note 12
The proportion of preterm births is calculated as weighted number of live births that occurred before 37 gestational weeks divided by weighted number of all live births. Live birth information, including gestational age and date of birth were obtained from the birth data.
The proportion of preterm births was calculated at the individual live-born infant level for both singleton and multiple gestations. Pregnancies resulting in both live births and stillbirths contributed only live-born infants to the analysis.
Gestational age is the number of completed weeks of pregnancy. In Canada, this is primarily measured using ultrasound, but it can also be estimated based on the interval between the first day of the mother’s last menstrual period and the day of delivery, or by physical examination or other methods..
Birthing mothers’ racialized group status was obtained from the 2021 Long-Form Census. It is possible that a proxy respondent, such as a spouse, reported a mother’s racialized group status on her behalf. For this Health Fact Sheet, ‘other racialized groups’ include Filipino, Arab, Latin American, Southeast Asian, West Asian, Korean, Japanese, racialized group not included elsewhere, and multiple racialized groups.
Indigenous population was excluded from this analysis. For birth outcomes disaggregated by Indigenous identity (First Nations, Métis and Inuit), please see: Birth outcomes among First Nations, Inuit and Métis populations.
Not all groups have sufficient counts to estimate preterm rate under 25. As a result, maternal age under 20 and maternal age between 20 and 24 were grouped together.
The 95% confidence interval (CI) illustrates the degree of variability associated with a rate. Wide confidence intervals indicate high variability. Thus, these rates should be interpreted with due caution.
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