J Clin Gynecol Obstet

Journal of Clinical Gynecology and Obstetrics, ISSN 1927-1271 print, 1927-128X online, Open Access

Article copyright, the authors; Journal compilation copyright, J Clin Gynecol Obstet and Elmer Press Inc

Journal website https://www.jcgo.org

Original Article

Volume 000, Number 000, September 2024, pages 000-000

Preterm Birth in Black Birthing People: A Systematic Literature Review and Meta-Analysis

Figure 2. Multi-level meta-analysis and pooled estimate of adjusted odds ratios (aORs) in nine studies for preterm birth (PTB).

Figure 3. Multi-level meta-analysis and pooled estimate of adjusted odds ratios (aORs) in two studies for low birth weight (LBW).

Figure 4. Multi-level meta-analysis and pooled estimate of adjusted odds ratios (aORs) in four studies for small for gestational age (SGA).

Figure 5. Multi-level meta-analysis and pooled adjusted odds ratios (aORs) for birth outcomes preterm birth (PTB), low birth weight (LBW), and small for gestational age (SGA) across different exposures.

**Table 1.** Summary of Studies Evaluating Preterm Birth in Canada and Preterm Birth in Black Population in Canada
Source	Objective	Study design	Sample size (N)	Exposures	Outcomes	Result summary	Point estimates (95% confidence interval)
cHTN: chronic hypertension; CS: cesarean section; GDM: gestational diabetes; gHTN: gestational hypertension; HTN: hypertension; LBW: low birth weight (< 2,500 g); LGA: large for gestational age (> 90th percentile); OR: odds ratio; aOR: adjusted odds ratio; P: P-value; PE: preeclampsia; PTB: preterm birth; sPTB: spontaneous preterm birth; RR: relative risk; aRR: adjusted relative risk; SES: socioeconomic status; SGA: small for gestational age (< 10th percentile); US: United States; SII: slope index of inequality.
Auger et al (2011) [23], Quebec, Canada	To determine whether educational inequalities in PTB have increased in Quebec, Canada from 1981 to 2006	Retrospective cohort study	N = 2,143,134	Maternal education	PTB: extreme (< 27), very (28 - 31), or moderate (< 32 - 36 weeks gestation)	“Absolute differences in the PTB proportion between the least and most educated mothers increased from 1981 to 2006 for extreme (adjusted SII 0.11% vs. 0.28%) and moderate PTB (adjusted SII 1.67% vs. 3.11%). Absolute differences in the proportion very PTB did not increase” [19]	N/A - aOR estimates provided as a yearly trend
Auger et al (2012) [24], Quebec, Canada	To evaluate adverse birth outcomes for Haitians in Quebec, Canada from 1981 to 2006	Retrospective cohort study	N = 2,143,134 Haitian: N = 31,663 Other Caribbean: N = 10,681 Other foreign: N = 230,692 Canadian: N = 1,841,396	Maternal origin/ethnicity (Haitian-born vs. Canadian-born)	PTB: extreme (< 27), very (28 - 31), or moderate (< 32 - 36 weeks gestation) LBW (< 2,500 g) SGA (< 10%)	“Relative to Canadian-born mothers, odds for Haitian-born mothers were four times greater for extreme PTB (< 27 weeks), twice greater for very PTB (28 - 31 weeks), and 25% higher for moderate PTB (32 - 36 weeks). Patterns similar for SGA birth and severe cases of LBW.”	PTB: aOR 1.44 (1.36 - 1.52) Extreme: aOR 3.99 (3.45 - 4.61) Very: aOR 1.99 (1.70 - 2.31) Moderate: aOR 1.25 (1.18 - 1.33) LBW: aOR 1.42 (1.34 - 1.5) SGA birth: aOR 1.09 (1.05 - 1.14)
Auger et al (2012) [25], Quebec, Canada	To determine whether socioeconomic (material) area context is more strongly related to PTB than social area characteristics from 1999 to 2006	Retrospective cohort study	N = 581,898	Two composite indices representing area-level material and social deprivation	PTB (< 37 weeks gestation)	“PTB rates were higher for areas with high material (7.1%) and social (6.8%) deprivation than those with low material (5.5%) and social (5.9%) deprivation.” Adjusted hazards of PTB were greater for material deprivation than social deprivation.	Material deprivation: aHR 1.26 (1.21 - 1.31) Social deprivation: aHR 1.07 (1.03 - 1.11)
Lee et al (2020) [26], Canada	To describe provincial time trends and variations in birth outcomes according to the 20 top maternal birthplaces from 2000 to 2016	Retrospective cohort study	N = 5,831,580 Immigrant: N = 1,562,835 Canadian-born: N = 4,268,745	Immigrant vs. Canadian-born	PTB (22 to 36 weeks gestation) Mean birth weight (at 39 to 40 weeks gestation)	“Compared with PTB rates among Canadian-born mothers, PTB rates were lower among various Asian, African, and Western immigrant groups and higher among those from Bangladesh, the Philippines, and the Caribbean. Lower birth weights were seen for most source countries, except the United States. These differences were uniform across the provinces, with a few exceptions.”	Northern Africa: aRR 0.69 (0.67 - 0.72) Sub-Saharan Africa: aRR 0.98 (0.95 - 1.00) Caribbean: aRR 1.39 (1.35 - 1.42)
Luo et al (2006) [27], Quebec, Canada	To determine the extent to which associations between adverse birth outcomes and SES can be identified using individual vs. community-level measures between 1991 and 2000	Retrospective cohort study	N = 825,349	Individual-level (maternal education), community-level (neighborhood income)	PTB (< 37 weeks gestation) SGA (< 10th percentile) Stillbirth	Compared to women in highest income quintile, women in lowest quintile were significantly more likely to have PTB, SGA, or stillbirth. Compared to mothers who completed community college or some university, mothers who completed less than high school were significantly more likely to have PTB, SGA, or stillbirth.	Income (low vs. high quintile): PTB: aOR 1.14 (1.10 - 1.17) SGA: aOR 1.18 (1.15 - 1.21) Stillbirth: aOR 1.30 (1.13 - 1.48) Education (less than high school vs. community college/some university): PTB: aOR 1.48 (1.44 - 1.52) SGA: aOR 1.86 (1.82 - 1.91) Stillbirth: aOR 1.54 (1.36 - 1.74)
McKinnon et al (2015) [28], Canada, United States	To compare differences in preterm birth between non-Hispanic Black and White women in Canada and the US from 2004 to 2006	Retrospective cohort study	Canada: N = 91,045 Black: N = 3,811 White: N = 87,234 US: N = 5,069,267 Black: N = 1,039,642 White: N = 4,029,625	Maternal race (Black vs. White)	PTB (< 37 weeks) Very PTB (< 32 weeks)	Adjusted risk ratios for PTB were slightly higher in Canada than in the US whereas adjusted risk differences were similar in both countries (P = 1.0). Similar patterns were observed for racial disparities in very PTB.	PTB: Canada: aRR 1.60 (1.39 - 1.81) US: aRR 1.45 (1.44 - 1.47) P = 0.1 Very PTB: Canada: 2.62 (1.83 - 3.41) US: 2.43 (2.36 - 2.52) P = 0.6
Menard et al (2020) [29], Montreal, Quebec, Canada	To characterize the rate of adverse pregnancy outcomes in a multicultural group of low-income women between 2013 and 2015	Retrospective cohort study	N = 1,387 Black: N = 418 White: N = 767 Asian: N = 202	Maternal race (Black vs. White), ethnicity, and immigration status (immigrant- vs. Canadian-born)	PTB (< 37 weeks) LBW (< 2,500 g) SGA (< 10%) LGA infants (> 90%) GDM Anemia Hypertension	Black women had higher risk of PTB, anemia, and hypertension compared to White women. Other outcomes were non-significant between Black and White women. Immigrants showed an increased risk of maternal anemia compared to Canadian-born women but similar risk PTB.	Race: PTB: aOR 1.79 (1.01 - 3.19) GDM: aOR 0.94 (0.64 - 1.38) Anemia: aOR 1.74 (1.29 - 2.35) HTN: aOR 2.23 (1.18 - 4.21) LBW: aOR 1.73 (0.88 - 3.00) SGA: aOR 1.24 (0.67 - 2.30) LGA: aOR 0.78 (0.51 - 1.18) Immigrants: PTB: aOR 0.98 (0.38 - 2.53) GDM: aOR 0.97 (0.51 - 1.82) Anemia: aOR 1.85 (1.06 - 3.21) HTN: aOR 0.71 (0.28 - 1.78) LBW: aOR 1.23 (0.40 - 3.78) SGA: aOR 1.02 (0.41 - 2.52) LGA: aOR 1.42 (0.67 - 2.99)
Miao et al (2022) [30], Ontario, Canada	To examine the inequities in adverse perinatal outcomes between Black and White pregnant people in Ontario between 2012 and 2019	Retrospective cohort study	N = 412,120 Black: N = 41,766 White: N = 370,344	Maternal race (Black vs. White)	PTB (< 37, < 34, < 32 weeks gestation), and other various adverse perinatal outcomes	“Black people were at an increased risk of GDM, preeclampsia, placental abruption, PTB (< 37, < 34, < 32 weeks), spontaneous PTB, all cesarean sections, emergency CS, LBW (< 2,500 g, < 1,500 g), SGA (< 10th percentile, < 3rd percentile) neonates, 5-min Apgar score < 4 and < 7, NICU admission, and hyperbilirubinemia requiring treatment but had lower risks of elective CS, assisted vaginal delivery, episiotomy, 3rd and 4th degree perineal tears, macrosomia, LGA neonates, and arterial cord pH < 7.1, as compared with White people. No differences in risks of gHTN and placenta previa were observed between Black and White people.”	PTB: < 37 weeks: aRR 1.41 (1.37 - 1.44), < 34 weeks: aRR 2.29 (2.23 - 2.35), < 32 weeks: aRR 2.85 (2.78 - 2.92) Spontaneous preterm birth: aRR 1.24 (1.17 - 1.30) GDM: aRR 1.08 (1.04 - 1.13) PE: aRR 1.1 (1.05 - 1.14) Placental abruption: aRR 1.11 (1.00 - 1.22) All cesarean section: aRR 1.11 (1.09 - 1.12) Emergency cesarean section: aRR 1.42 (1.40 - 1.44) Elective cesarean section: aRR 0.91 (0.89 - 0.93) Assisted vaginal delivery: aRR 0.83 (0.79 - 0.87) Episiotomy: aRR 0.71 (0.67 - 0.76) 3rd and 4th degree perineal tears: aRR 0.72 (0.64 - 0.81) gHTN: aRR 1.01 (0.96 - 1.06) Placenta previa: aRR 1.02 (0.89 - 1.15)
Rey (1997) [31], Canada	To compare the incidence of preeclampsia and neonatal outcomes in white (born in Canada) and black (born in Haiti) women with mild chronic hypertension between 1978 and 1991	Case-control study	Cases: N = 282 Black: N = 74 White: N = 208 Controls: N = 20,077 Black: N = 2,400 White: N = 17,677	Maternal origin/race: black (Haitian-born) vs. white (Canadian-born)	Superimposed preeclampsia (siPEC) Perinatal mortality PTB (< 37 weeks gestation) SGA (< 10%)	“siPEC (32.4% vs. 14.9%; P < 0.01), perinatal mortality (9.5% vs. 2.9%; P < 0.05) and prematurity (32.4% vs. 19.7%; P < 0.05) were more frequent in Black than in White women with cHTN. Within both races, cHTN women with siPEC demonstrated higher rates of perinatal mortality and morbidity than controls.	cHTN women and race: siPEC: RR 2.7 (1.5 - 5.1) Perinatal mortality: RR 3.5 (1.1 - 10.9) PTB: RR 1.9 (1.1 - 3.5) SGA: RR 1.5 (0.7 - 3.0)
Tabatabaei et al (2017) [32], Quebec, Canada	To explore the relation between maternal plasma 25(OH)D concentration in the first trimester (8 -14 weeks of gestation) and the risk of preterm and spontaneous preterm births (< 37 weeks of gestation) by ethnicity	Case-control study	N = 472 Cases: N = 118 Controls: N = 354	Maternal vitamin D level (< 50, 50 - 75, and > 75 nmol/L) (ethnic vs. non-ethnic)	PTB spontaneous PTB (< 37 weeks gestation)	“The distributions of maternal vitD status (< 50, 50 - 75, and > 75 nmol/L) were different in preterm and spontaneous PTB cases compared with controls but only in women of ethnic minority (P = 0.003 and 0.024, respectively). Among ethnic subgroups, sub-Saharan Africans (P = 0.030) and Arab-West Asians (P = 0.045) showed an inverse relation between maternal vitD status and the risk of PTB.”	Vitamin D level (30 vs. 75 nmol/L) PTB, non-ethnic: aOR 0.94 (0.48 - 1.82) PTB, ethnic: aOR 4.05 (1.16 - 14.12) sPTB, non-ethnic: aOR 1.04 (0.52 - 2.10) sPTB, ethnic: aOR 1.75 (0.39 - 7.79)

Table 1. Summary of Studies Evaluating Preterm Birth in Canada and Preterm Birth in Black Population in Canada

Source

Objective

Study design

Sample size (N)

Exposures

Outcomes

Result summary

Point estimates (95% confidence interval)

cHTN: chronic hypertension; CS: cesarean section; GDM: gestational diabetes; gHTN: gestational hypertension; HTN: hypertension; LBW: low birth weight (< 2,500 g); LGA: large for gestational age (> 90th percentile); OR: odds ratio; aOR: adjusted odds ratio; P: P-value; PE: preeclampsia; PTB: preterm birth; sPTB: spontaneous preterm birth; RR: relative risk; aRR: adjusted relative risk; SES: socioeconomic status; SGA: small for gestational age (< 10th percentile); US: United States; SII: slope index of inequality.

Auger et al (2011) [23], Quebec, Canada

To determine whether educational inequalities in PTB have increased in Quebec, Canada from 1981 to 2006

Retrospective cohort study

N = 2,143,134

Maternal education

PTB: extreme (< 27), very (28 - 31), or moderate (< 32 - 36 weeks gestation)

“Absolute differences in the PTB proportion between the least and most educated mothers increased from 1981 to 2006 for extreme (adjusted SII 0.11% vs. 0.28%) and moderate PTB (adjusted SII 1.67% vs. 3.11%). Absolute differences in the proportion very PTB did not increase” [19]

N/A - aOR estimates provided as a yearly trend

Auger et al (2012) [24], Quebec, Canada

To evaluate adverse birth outcomes for Haitians in Quebec, Canada from 1981 to 2006

Retrospective cohort study

N = 2,143,134
Haitian: N = 31,663
Other Caribbean: N = 10,681
Other foreign: N = 230,692
Canadian: N = 1,841,396

Maternal origin/ethnicity (Haitian-born vs. Canadian-born)

PTB: extreme (< 27), very (28 - 31), or moderate (< 32 - 36 weeks gestation)
LBW (< 2,500 g)
SGA (< 10%)

“Relative to Canadian-born mothers, odds for Haitian-born mothers were four times greater for extreme PTB (< 27 weeks), twice greater for very PTB (28 - 31 weeks), and 25% higher for moderate PTB (32 - 36 weeks). Patterns similar for SGA birth and severe cases of LBW.”

PTB: aOR 1.44 (1.36 - 1.52)
Extreme: aOR 3.99 (3.45 - 4.61)
Very: aOR 1.99 (1.70 - 2.31)
Moderate: aOR 1.25 (1.18 - 1.33)
LBW: aOR 1.42 (1.34 - 1.5)
SGA birth: aOR 1.09 (1.05 - 1.14)

Auger et al (2012) [25], Quebec, Canada

To determine whether socioeconomic (material) area context is more strongly related to PTB than social area characteristics from 1999 to 2006

Retrospective cohort study

N = 581,898

Two composite indices representing area-level material and social deprivation

PTB (< 37 weeks gestation)

“PTB rates were higher for areas with high material (7.1%) and social (6.8%) deprivation than those with low material (5.5%) and social (5.9%) deprivation.” Adjusted hazards of PTB were greater for material deprivation than social deprivation.

Material deprivation: aHR 1.26 (1.21 - 1.31)
Social deprivation: aHR 1.07 (1.03 - 1.11)

Lee et al (2020) [26], Canada

To describe provincial time trends and variations in birth outcomes according to the 20 top maternal birthplaces from 2000 to 2016

Retrospective cohort study

N = 5,831,580
Immigrant: N = 1,562,835
Canadian-born: N = 4,268,745

Immigrant vs. Canadian-born

PTB (22 to 36 weeks gestation)
Mean birth weight (at 39 to 40 weeks gestation)

“Compared with PTB rates among Canadian-born mothers, PTB rates were lower among various Asian, African, and Western immigrant groups and higher among those from Bangladesh, the Philippines, and the Caribbean. Lower birth weights were seen for most source countries, except the United States. These differences were uniform across the provinces, with a few exceptions.”

Northern Africa: aRR 0.69 (0.67 - 0.72)
Sub-Saharan Africa: aRR 0.98 (0.95 - 1.00)
Caribbean: aRR 1.39 (1.35 - 1.42)

Luo et al (2006) [27], Quebec, Canada

To determine the extent to which associations between adverse birth outcomes and SES can be identified using individual vs. community-level measures between 1991 and 2000

Retrospective cohort study

N = 825,349

Individual-level (maternal education), community-level (neighborhood income)

PTB (< 37 weeks gestation)
SGA (< 10th percentile)
Stillbirth

Compared to women in highest income quintile, women in lowest quintile were significantly more likely to have PTB, SGA, or stillbirth. Compared to mothers who completed community college or some university, mothers who completed less than high school were significantly more likely to have PTB, SGA, or stillbirth.

Income (low vs. high quintile):
PTB: aOR 1.14 (1.10 - 1.17)
SGA: aOR 1.18 (1.15 - 1.21)
Stillbirth: aOR 1.30 (1.13 - 1.48)
Education (less than high school vs. community college/some university):
PTB: aOR 1.48 (1.44 - 1.52)
SGA: aOR 1.86 (1.82 - 1.91)
Stillbirth: aOR 1.54 (1.36 - 1.74)

McKinnon et al (2015) [28], Canada, United States

To compare differences in preterm birth between non-Hispanic Black and White women in Canada and the US from 2004 to 2006

Retrospective cohort study

Canada: N = 91,045
Black: N = 3,811
White: N = 87,234
US: N = 5,069,267
Black: N = 1,039,642
White: N = 4,029,625

Maternal race (Black vs. White)

PTB (< 37 weeks)
Very PTB (< 32 weeks)

Adjusted risk ratios for PTB were slightly higher in Canada than in the US whereas adjusted risk differences were similar in both countries (P = 1.0). Similar patterns were observed for racial disparities in very PTB.

PTB:
Canada: aRR 1.60 (1.39 - 1.81)
US: aRR 1.45 (1.44 - 1.47)
P = 0.1
Very PTB:
Canada: 2.62 (1.83 - 3.41)
US: 2.43 (2.36 - 2.52)
P = 0.6

Menard et al (2020) [29], Montreal, Quebec, Canada

To characterize the rate of adverse pregnancy outcomes in a multicultural group of low-income women between 2013 and 2015

Retrospective cohort study

N = 1,387
Black: N = 418
White: N = 767
Asian: N = 202

Maternal race (Black vs. White), ethnicity, and immigration status (immigrant- vs. Canadian-born)

PTB (< 37 weeks)
LBW (< 2,500 g)
SGA (< 10%)
LGA infants (> 90%)
GDM
Anemia
Hypertension

Black women had higher risk of PTB, anemia, and hypertension compared to White women. Other outcomes were non-significant between Black and White women. Immigrants showed an increased risk of maternal anemia compared to Canadian-born women but similar risk PTB.

Race:
PTB: aOR 1.79 (1.01 - 3.19)
GDM: aOR 0.94 (0.64 - 1.38)
Anemia: aOR 1.74 (1.29 - 2.35)
HTN: aOR 2.23 (1.18 - 4.21)
LBW: aOR 1.73 (0.88 - 3.00)
SGA: aOR 1.24 (0.67 - 2.30)
LGA: aOR 0.78 (0.51 - 1.18)
Immigrants:
PTB: aOR 0.98 (0.38 - 2.53)
GDM: aOR 0.97 (0.51 - 1.82)
Anemia: aOR 1.85 (1.06 - 3.21)
HTN: aOR 0.71 (0.28 - 1.78)
LBW: aOR 1.23 (0.40 - 3.78)
SGA: aOR 1.02 (0.41 - 2.52)
LGA: aOR 1.42 (0.67 - 2.99)

Miao et al (2022) [30], Ontario, Canada

To examine the inequities in adverse perinatal outcomes between Black and White pregnant people in Ontario between 2012 and 2019

Retrospective cohort study

N = 412,120
Black: N = 41,766
White: N = 370,344

Maternal race (Black vs. White)

PTB (< 37, < 34, < 32 weeks gestation), and other various adverse perinatal outcomes

“Black people were at an increased risk of GDM, preeclampsia, placental abruption, PTB (< 37, < 34, < 32 weeks), spontaneous PTB, all cesarean sections, emergency CS, LBW (< 2,500 g, < 1,500 g), SGA (< 10th percentile, < 3rd percentile) neonates, 5-min Apgar score < 4 and < 7, NICU admission, and hyperbilirubinemia requiring treatment but had lower risks of elective CS, assisted vaginal delivery, episiotomy, 3rd and 4th degree perineal tears, macrosomia, LGA neonates, and arterial cord pH < 7.1, as compared with White people. No differences in risks of gHTN and placenta previa were observed between Black and White people.”

PTB:
< 37 weeks: aRR 1.41 (1.37 - 1.44),
< 34 weeks: aRR 2.29 (2.23 - 2.35),
< 32 weeks: aRR 2.85 (2.78 - 2.92)
Spontaneous preterm birth: aRR 1.24 (1.17 - 1.30)
GDM: aRR 1.08 (1.04 - 1.13)
PE: aRR 1.1 (1.05 - 1.14)
Placental abruption: aRR 1.11 (1.00 - 1.22)
All cesarean section: aRR 1.11 (1.09 - 1.12)
Emergency cesarean section: aRR 1.42 (1.40 - 1.44)
Elective cesarean section: aRR 0.91 (0.89 - 0.93)
Assisted vaginal delivery: aRR 0.83 (0.79 - 0.87)
Episiotomy: aRR 0.71 (0.67 - 0.76)
3rd and 4th degree perineal tears: aRR 0.72 (0.64 - 0.81)
gHTN: aRR 1.01 (0.96 - 1.06)
Placenta previa: aRR 1.02 (0.89 - 1.15)

Rey (1997) [31], Canada

To compare the incidence of preeclampsia and neonatal outcomes in white (born in Canada) and black (born in Haiti) women with mild chronic hypertension between 1978 and 1991

Case-control study

Cases: N = 282
Black: N = 74
White: N = 208
Controls: N = 20,077
Black: N = 2,400
White: N = 17,677

Maternal origin/race: black (Haitian-born) vs. white (Canadian-born)

Superimposed preeclampsia (siPEC)
Perinatal mortality
PTB (< 37 weeks gestation)
SGA (< 10%)

“siPEC (32.4% vs. 14.9%; P < 0.01), perinatal mortality (9.5% vs. 2.9%; P < 0.05) and prematurity (32.4% vs. 19.7%; P < 0.05) were more frequent in Black than in White women with cHTN. Within both races, cHTN women with siPEC demonstrated higher rates of perinatal mortality and morbidity than controls.

cHTN women and race:
siPEC: RR 2.7 (1.5 - 5.1)
Perinatal mortality: RR 3.5 (1.1 - 10.9)
PTB: RR 1.9 (1.1 - 3.5)
SGA: RR 1.5 (0.7 - 3.0)

Tabatabaei et al (2017) [32], Quebec, Canada

To explore the relation between maternal plasma 25(OH)D concentration in the first trimester (8 -14 weeks of gestation) and the risk of preterm and spontaneous preterm births (< 37 weeks of gestation) by ethnicity

Case-control study

N = 472
Cases: N = 118
Controls: N = 354

Maternal vitamin D level (< 50, 50 - 75, and > 75 nmol/L)
(ethnic vs. non-ethnic)

PTB
spontaneous PTB (< 37 weeks gestation)

“The distributions of maternal vitD status (< 50, 50 - 75, and > 75 nmol/L) were different in preterm and spontaneous PTB cases compared with controls but only in women of ethnic minority (P = 0.003 and 0.024, respectively). Among ethnic subgroups, sub-Saharan Africans (P = 0.030) and Arab-West Asians (P = 0.045) showed an inverse relation between maternal vitD status and the risk of PTB.”

Vitamin D level (30 vs. 75 nmol/L)
PTB, non-ethnic: aOR 0.94 (0.48 - 1.82)
PTB, ethnic: aOR 4.05 (1.16 - 14.12)
sPTB, non-ethnic: aOR 1.04 (0.52 - 2.10)
sPTB, ethnic: aOR 1.75 (0.39 - 7.79)

**Table 2.** Quality Assessment of the Retrospective Cohort Studies (n = 8) Examining Preterm Birth in the Black Population in Canada Using the Modified Newcastle-Ottawa Scale
Author, year	Selection	Comparability	Outcome	Quality
Good quality: 3 or 4 “yes” in selection domain AND 1 “yes” in comparability domain AND 2 or 3 “yes” in outcome/exposure domain; Fair quality: 2 “yes” in selection domain AND 1 “yes” in comparability domain AND 2 or 3 “yes” in outcome/exposure domain. Poor quality: 0 or 1 “yes” in selection domain OR 0 “yes” in comparability domain or 0 or 1 “yes” in outcome/exposure domain. Y: yes; N: no; U: uncertain.
Auger et al (2011) [23]	Y	Y	Y	N	Y	Y	Y	Y	Good (7/8)
Auger et al (2012) [24]	Y	Y	Y	N	Y	Y	Y	Y	Good (7/8)
Auger et al (2012) [25]	Y	Y	Y	N	Y	Y	Y	Y	Good (7/8)
Lee et al (2020) [26]	Y	Y	Y	N	Y	Y	Y	Y	Good (7/8)
Luo et al (2006) [27]	Y	Y	Y	N	Y	Y	Y	Y	Good (7/8)
McKinnon et al (2015) [28]	Y	Y	Y	N	Y	Y	Y	Y	Good (7/8)
Menard et al (2020) [29]	N	Y	Y	N	Y	Y	Y	Y	Fair (6/8)
Miao et al (2022) [30]	U	Y	U	N	Y	Y	Y	Y	Poor (5/8)

Table 2. Quality Assessment of the Retrospective Cohort Studies (n = 8) Examining Preterm Birth in the Black Population in Canada Using the Modified Newcastle-Ottawa Scale

Author, year

Selection

Comparability

Outcome

Quality

Representativeness of exposed cohort

Selection of non-exposed cohort same as exposed

Ascertainment of exposure

Demonstration of outcome of interest not part of beginning of study

Comparable for primary/secondary items (adjusted for confounders)

Assessment of outcomes

Follow-up long enough

Adequacy of follow-up cohorts

Good quality: 3 or 4 “yes” in selection domain AND 1 “yes” in comparability domain AND 2 or 3 “yes” in outcome/exposure domain; Fair quality: 2 “yes” in selection domain AND 1 “yes” in comparability domain AND 2 or 3 “yes” in outcome/exposure domain. Poor quality: 0 or 1 “yes” in selection domain OR 0 “yes” in comparability domain or 0 or 1 “yes” in outcome/exposure domain. Y: yes; N: no; U: uncertain.

Auger et al (2011) [23]

Good (7/8)

Auger et al (2012) [24]

Good (7/8)

Auger et al (2012) [25]

Good (7/8)

Lee et al (2020) [26]

Good (7/8)

Luo et al (2006) [27]

Good (7/8)

McKinnon et al (2015) [28]

Good (7/8)

Menard et al (2020) [29]

Fair (6/8)

Miao et al (2022) [30]

Poor (5/8)

**Table 3.** Quality Assessment of the Case-Control Studies (n = 2) Examining Preterm Birth in the Black Population in Canada Using the Modified Newcastle-Ottawa Scale
Author, year	Selection	Comparability	Exposure	Quality
Good quality: 3 or 4 stars in selection domain AND 1 star in comparability domain AND 2 or 3 stars in outcome/exposure domain; Fair quality: 2 stars in selection domain AND 1 star in comparability domain AND 2 or 3 stars in outcome/exposure domain. Poor quality: 0 or 1 star in selection domain OR 0 stars in comparability domain or 0 or 1 star in outcome/exposure domain. Y: yes; N: no; U: uncertain.
Rey (1997) [31]	U	Y	Y	Y	Y	U	Y	U	Poor (5/8)
Tabatabaei et al (2017) [32]	Y	Y	Y	Y	Y	Y	Y	Y	Good (8/8)

Table 3. Quality Assessment of the Case-Control Studies (n = 2) Examining Preterm Birth in the Black Population in Canada Using the Modified Newcastle-Ottawa Scale

Author, year

Selection

Comparability

Exposure

Quality

Adequate case definition

Representativeness of cases

Selection of controls

Definition of controls

Comparable for primary/secondary items (adjusted for confounders)

Ascertainment of exposure

Same method for cases/controls

Non-response rate

Good quality: 3 or 4 stars in selection domain AND 1 star in comparability domain AND 2 or 3 stars in outcome/exposure domain; Fair quality: 2 stars in selection domain AND 1 star in comparability domain AND 2 or 3 stars in outcome/exposure domain. Poor quality: 0 or 1 star in selection domain OR 0 stars in comparability domain or 0 or 1 star in outcome/exposure domain. Y: yes; N: no; U: uncertain.

Rey (1997) [31]

Poor (5/8)

Tabatabaei et al (2017) [32]

Good (8/8)