ImportanceEvidence indicates that immigrant women and women residing within low-income neighborhoods experience higher adversity during pregnancy. Little is known about the comparative risk of severe maternal morbidity or mortality (SMM-M) among immigrant vs nonimmigrant women living in low-income areas.ObjectiveTo compare the risk of SMM-M between immigrant and nonimmigrant women residing exclusively within low-income neighborhoods in Ontario, Canada.Design, Setting, and ParticipantsThis population-based cohort study used administrative data for Ontario, Canada, from April 1, 2002, to December 31, 2019. Included were all 414 337 hospital-based singleton live births and stillbirths occurring between 20 and 42 weeks’ gestation, solely among women residing in an urban neighborhood of the lowest income quintile; all women were receiving universal health care insurance. Statistical analysis was performed from December 2021 to March 2022.ExposuresNonrefugee immigrant status vs nonimmigrant status.Main Outcomes and MeasuresThe primary outcome, SMM-M, was a composite outcome of potentially life-threatening complications or mortality occurring within 42 days of the index birth hospitalization. A secondary outcome was SMM severity, approximated by the number of SMM indicators (0, 1, 2 or ≥3 indicators). Relative risks (RRs), absolute risk differences (ARDs), and odds ratios (ORs) were adjusted for maternal age and parity.ResultsThe cohort included 148 085 births to immigrant women (mean [SD] age at index birth, 30.6 [5.2] years) and 266 252 births to nonimmigrant women (mean [SD] age at index birth, 27.9 [5.9] years). Most immigrant women originated from South Asia (52 447 [35.4%]) and the East Asia and Pacific (35 280 [23.8%]) regions. The most frequent SMM indicators were postpartum hemorrhage with red blood cell transfusion, intensive care unit admission, and puerperal sepsis. The rate of SMM-M was lower among immigrant women (2459 of 148 085 [16.6 per 1000 births]) than nonimmigrant women (4563 of 266 252 [17.1 per 1000 births]), equivalent to an adjusted RR of 0.92 (95% CI, 0.88-0.97) and an adjusted ARD of −1.5 per 1000 births (95% CI, −2.3 to −0.7). Comparing immigrant vs nonimmigrant women, the adjusted OR of having 1 SMM indicator was 0.92 (95% CI, 0.87-0.98), the adjusted OR of having 2 indicators was 0.86 (95% CI, 0.76-0.98), and the adjusted OR of having 3 or more indicators was 1.02 (95% CI, 0.87-1.19).Conclusions and RelevanceThis study suggests that, among universally insured women residing in low-income urban areas, immigrant women have a slightly lower associated risk of SMM-M than their nonimmigrant counterparts. Efforts aimed at improving pregnancy care should focus on all women residing in low-income neighborhoods.

Neonatal morbidity and mortality are important public health indicators used to monitor and evaluate neonatal health and quality of perinatal care. 1,2 The neonatal period, ranging from birth to 27 days thereafter, is the most vulnerable time for infant survival. 1 Around 75% of infant deaths occur during this period, largely from prematurity and other conditions that can often be prevented by timely obstetrical and neonatal care. 3,4 In high-income countries, improvements in health care have resulted in a decline in neonatal mortality, 5,6 including in Canada, where the rate is 3.6 deaths per 1000 live births. 7 Accordingly, research and public health surveillance has increasingly focused on severe neonatal morbidity (SNM), which refers to a newborn who has survived a severe complication during birth or the neonatal period. 1,8,9 Identifying newborns at high risk of SNM is crucial as it has serious implications for the surviving child and their family. 10,11 Limited research has examined SNM in high-income countries. 2,6,8,[12][13][14][15][16][17] Studies have primarily focused on deriving and validating the criteria to define SNM, 1,3,10 quantifying the prevalence of SNM and identifying risk factors in African, Asian and Latin American regions. 11,[18][19][20][21][22][23][24][25][26][27] Research is also lacking on a range of upstream social determinants of health inequity and their influence on SNM. 28,29 Living in a low-income area 12,[30][31][32][33][34][35] and being an