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Birth outcomes among First Nations, Inuit and Métis populations

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by Amanda J. Sheppard, Gabriel D. Shapiro, Tracey Bushnik, Russell Wilkins, Serenity Perry, Jay S. Kaufman, Michael S. Kramer and Seungmi Yang

Birth outcomes among Indigenous peoples―First Nations, Inuit and Métis―are consistently reported to be less favourable than among the non-Indigenous population.^{Note 1} However, relatively little information is available at the national level for Indigenous people overall or for specific Indigenous identity groups, who have unique languages, customs, cultures, and colonial experiences.

A systematic review and meta-analyses of birth outcomes among Indigenous women (predominantly from Canada, the United States and Australia) outlined factors associated with the higher risk: reduced access to standard prenatal care; inaccurate estimation of gestational age and subsequent complications of post-term pregnancies; pre-existing medical conditions; high rates of multiparity; young maternal age; marital status; and low educational attainment.^{Note 2} The determinants extend beyond health behaviours and socioeconomic characteristics^{Note 3} to include the legacy of policies that have resulted in intergenerational trauma that has affected the physical and mental health of individuals, families and communities.^{Note 4Note 5} As well, jurisdictional responsibilities for the provision of Indigenous health services are complex and vary by region; difficulties are heightened in small and remote communities.^{Note 6Note 7}

Data on perinatal outcomes among First Nations and Inuit are limited to the provinces of Quebec (an indicator of first language spoken is used as a proxy to identify First Nations and Inuit^{Note 8}), Manitoba (First Nations status is assigned via parental self-identification^{Note 9}), and British Columbia (self-identification and record linkage are used to identify First Nations^{Note 10}), and the Inuit land claims settlement areas (most infants are assumed to be of Inuit ancestry^{Note 11}). Data on Métis birth outcomes are available only for Manitoba, where Métis identity has been established through the Manitoba Métis Federation membership list and self-identification in the Canadian Community Health Survey and the National Population Health Survey.^{Note 12}

Owing to the lack of consistent data, the use of different methods of analysis, and the rarity of some birth outcomes, widely varying estimates have been published for preterm births^{Note 13Note 14Note 15Note 16Note 17}; small-for-gestational-age births^{Note 9Note 10Note 13Note 15Note 18}; large-for-gestational-age births ^{Note 8Note 9Note 10Note 15Note 18}; stillbirths^{Note 13Note 15Note 17}; and infant mortality^{Note 9Note 10Note 13Note 15Note 18} among Indigenous people.

This study examines adverse perinatal outcomes among First Nations, Inuit, and Métis in a nationally representative sample, based on birth and death registrations that were linked with census data. The main objective is to describe and compare rates of preterm birth, small-for-gestational-age birth, large-for-gestational-age birth, stillbirth, and infant mortality (neonatal, postneonatal, and cause-specific) in an inclusive sample of the three Indigenous groups and the non-Indigenous population during the 2004-to-2006 period.

Data and methods

Data sources

The analysis pertains to a cohort of singleton births (May 16, 2004 through May 15, 2006) created by linking the Canadian Live Birth, Infant Death and Stillbirth Database to results from the 2006 Census, the latest census available with a long-form questionnaire. Linkage was established according to the child’s date of birth and sex, maternal and paternal dates and places of birth, and postal code. An overall linkage rate of 90% was achieved, with a false-positive match rate of less than 1%. The methods used to generate this dataset are described elsewhere.^{Note 19}

The long-form census questionnaire was distributed to 20% of households. It obtained data on socioeconomic and demographic characteristics, including Indigenous identity. First Nations people living off reserve, Inuit living outside their traditional territories, and Métis people would be randomly selected in those households. As well, reserve communities and remote areas were oversampled; that is, 100% of households in these areas were asked to complete the long-form questionnaire.^{Note 20} The dataset, therefore, provides perinatal information for a nationally representative cohort of births that includes identifiers for First Nations, Inuit and Métis.

Indigenous identity

Indigenous identity was determined with the 2006 Census question: “Is this person an Aboriginal person, that is, North America Indian, Métis or Inuit (Eskimo)?” Response options were “No,” “Yes, North American Indian,” “Yes, Métis,” or “Yes, Inuit (Eskimo).” The term “Indigenous” refers to those who replied “Yes” to any of these responses; “First Nations” refers to those who replied “Yes, North American Indian.” For the present analysis, census respondents who reported more than one Indigenous identity (0.3% of the combined Indigenous category) were included in the Indigenous total, but excluded from the specific groups.

Outcomes and descriptive factors

The perinatal outcomes were: preterm birth (before 37 weeks of completed gestation), small-for-gestational-age birth (sex-specific birth weight below the 10th percentile for gestational age, based on the Canadian reference^{Note 21}), large-for-gestational-age birth (sex-specific birth weight above the 90th percentile for gestational age), stillbirth, all-cause infant death, neonatal death, postneonatal death, and cause-specific infant death. Maternal age, paternal age, perinatal outcomes, and parity were from the birth registry data. Cause of death was determined from International Statistical Classification of Diseases and Health Problems, Tenth Revision (ICD-10) codes in death registry data and coded according to modified International Collaborative Effort on Perinatal and Infant Mortality groupings.^{Note 22} Marital status and maternal education were from the census.

Statistical analyses

Parental characteristics and adverse birth outcomes were compared by Indigenous identity. The analyses were restricted to singleton births because multiples are more likely to have adverse outcomes such as perinatal mortality.^{Note 23}

To address concerns about the quality of birth registration data in Ontario, a sensitivity analysis was conducted to assess the effect of omitting that province from the study.^{Note 22Note 24} After review, the Ontario data were retained because no clear evidence of bias was observed (Ontario data are available on request). This allowed the inclusion of an additional 2,085 births to Indigenous mothers (First Nations = 1,754; Métis = 302; Inuit = 22; multiple Indigenous identities = 7), which amounted to 12% of all Indigenous births in the cohort.

The distribution of study factors was compared by group. All analyses were weighted with the cohort sampling weight, and confidence intervals (CI) were calculated using bootstrap weights to account for sampling, non-response, and the linkage process.^{Note 19} To determine the upper 95% confidence limit for cause-specific mortality rates of 0, the upper 95% confidence limit, based on a presumed Poisson distribution with 0 observed events, was divided by the unweighted denominator. All data analyses were carried out using SAS, Version 9.1.

Results

The cohort consisted of 17,547 Indigenous and 112,112 non-Indigenous singleton births. First Nations accounted for the majority (77%) of Indigenous births.

Overall, First Nations, Inuit and Métis mothers were younger, less likely to be married or in a common-law union, less likely to have graduated from secondary school, and had had more previous births than did non-Indigenous mothers (Table 1). Paternal age tended to be younger for Indigenous than non-Indigenous births, but was missing from the records more often (18% versus 4%).

Among the Indigenous groups, Inuit mothers were the youngest (24% were younger than age 20), the most likely to be unmarried (82%), and the least likely to be secondary graduates (62%); nearly 30% of them had had at least three previous live births. Métis mothers were the most likely to have a university degree (9%) and the least likely to be younger than 20 (13%).

Except for small-for-gestational-age births, Indigenous infants had higher rates of adverse birth outcomes than did non-Indigenous infants (Table 2). Inuit infants had the highest rate of preterm birth (11.4%; 95% CI: 9.7% to 13.1%). First Nations infants had the lowest rate of small-for-gestational-age birth (5.8%; 95% CI: 5.2% to 6.3%) and the highest rate of large-for-gestational-age birth (20.9%; CI: 19.9% to 21.8%).

Infant mortality rates were more than twice as high for each Indigenous group, compared with the non-Indigenous population. Postneonatal deaths made up nearly half of all infant deaths in the Indigenous population, compared with about one-quarter of all infant deaths in the non-Indigenous population.

Rates of death from sudden infant death syndrome (SIDS—a sudden and unexpected death of an apparently healthy infant younger than age 1) were more than seven times higher in the First Nations and Inuit populations (2.2; 95% CI: 1.4 to 3.6 and 2.5; 95% CI: 1.9 to 3.3 per 1,000 live births, respectively) than in the non-Indigenous population (0.3; 95% CI: 0.2 to 0.5) (Table 3). SIDS accounted for 24% of First Nations infant deaths and 21% of Inuit infant deaths and was the leading cause of infant mortality in both groups, whereas it accounted for 7% of non-Indigenous infant deaths. Owing to small cell counts, cause-specific mortality rates for Métis and Inuit were generally not reportable.

Discussion

The census-linked 2004-to-2006 birth cohort offers an opportunity to investigate birth outcomes for First Nations, Inuit, and Métis at the national level. The findings confirm previous reports of disparities between Indigenous and non-Indigenous Canadians and enhance that information with comparisons of the three major Indigenous groups.

Earlier research has shown elevated rates of preterm birth, large-for-gestational-age birth, stillbirth, and infant death among First Nations mothers compared with non-Indigenous mothers, and higher rates of large-for-gestational-age birth and stillbirth among First Nations, compared with Inuit and Métis. Pre-existing diabetes,^{Note 25} inadequate prenatal care,^{Note 26} and mothers who, themselves, were born preterm or were large-for-gestational-age have been reported as risks for these outcomes.^{Note 2} Additionally, many Indigenous people live in remote or rural communities, where the turnover rate among health providers is high; Indigenous health professionals are scarce; and funding and jurisdictional issues may impede access to health care.^{Note 7}

The analysis confirms the previously reported elevated rate of preterm birth among Inuit mothers.^{Note 13Note 27} Possible explanations include high fertility, young maternal age, increased susceptibility to infections (bacterial vaginosis),^{Note 11Note 28Note 29} and stress due to medical evacuation for childbirth.^{Note 30} Mortality among Inuit infants was evenly distributed between the first month (often associated with preterm or small-for-gestational-age birth) and subsequent months of the first year of life (commonly a result of SIDS or injury). These results parallel a study of infant mortality among Inuit in Nunavut from 1999 through 2011, which reported the leading causes of death (when documented; n = 95) to be sudden unexpected death in infancy, SIDS, and infection.^{Note 28} Factors such as the baby’s sleep environment, overcrowding, high maternal smoking rates (up to 80%),^{Note 16} and preterm birth may partly explain high mortality among Inuit infants.

Métis tend to be under-represented in the peer-reviewed literature.^{Note 31} Nonetheless, findings have suggested poorer health outcomes compared with non-Indigenous people, but generally more favourable outcomes compared with other Indigenous groups.^{Note 29Note 32Note 33Note 34Note 35} A provincial report based on linked data from the Manitoba Métis Federation membership and national surveys reported higher rates of teenage pregnancies and lower rates of breastfeeding initiation among Métis than among other Manitoba mothers, but comparable newborn hospital readmission rates within four weeks of discharge.^{Note 12} Infant mortality rates were slightly lower among Métis, than among non-Indigenous Manitobans (5.7 versus 6.8 per 1,000 births).^{Note 12} The Manitoba Métis infant mortality rate is substantially lower than the national rate reported in this analysis (7.1 per 1,000), while the Manitoba non-Indigenous rate exceeds the national rate (4.4 per 1,000). Additional research is necessary to understand these differences, and to explain the higher likelihood of neonatal versus postneonatal deaths among Métis infants.

Elevated rates of SIDS in the First Nations and Inuit populations are not a novel finding, but are of major public health importance.^{Note 28}

Limitations

The overall linkage rate between the 2006 Census and the Canadian Live Birth, Infant Death and Stillbirth Database was 90% for the cohort, yielding estimates of adverse birth outcomes across Indigenous identity groups and maternal levels of education with minimal selection bias.^{Note 20} However, the dataset is subject to limitations that specifically concern analyses of Indigenous people, and the prevalence of adverse birth outcomes among First Nations, Inuit, and Métis may be underestimated.

Pregnancies that resulted in stillbirths and infant deaths were less likely to be linked to the 2006 Census, since fewer variables were available for matching. Births to mothers younger than age 25 and births in British Columbia, the Northwest Territories, and Nunavut were also linked less frequently.^{Note 19} Because 99% of the Indigenous population in Nunavut in 2006 was Inuit, and the data show that 24% of Inuit mothers were younger than age 20, the potential for biased estimates is greater for this group. Linkage was also compromised by birth records that lacked postal code, child sex, date of birth, age of mother, or maternal place of birth.

Long-form census data were not collected for residents of institutions (such as hospitals, nursing homes, jails) or shelters. Indigenous people are more likely than non-Indigenous people to live in shelters or correctional facilities.^{Note 36Note 37} Consequently, pregnancy outcomes for the most vulnerable Indigenous women may not have been captured.

Also, causes of death may be less reliably reported in remote Indigenous communities. This would reduce the accuracy of findings for rare causes of infant deaths (many of which were already imprecise or unreportable due to small cell counts).^{Note 38}

Finally, the data are more than 10 years old.

Conclusion

Before the creation of this cohort, analyses of birth outcomes in Canada were limited by the lack of Indigenous identifiers on birth registrations. The census-linked birth data can be used to compare perinatal outcomes among the three major Indigenous groups. The results confirm disparities in birth outcomes between Indigenous and non-Indigenous women and reveal differences among First Nations, Inuit, and Métis. The cause-specific infant mortality findings reveal disparities in SIDS rates and highlight the need for targeted interventions to reduce SIDS in First Nations and Inuit populations. More generally, greater health literacy, access to prenatal care, local birthing opportunities, and postpartum support may help improve the long-term health of First Nations, Inuit, and Métis infants, women, families, and communities.