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Concomitant preterm birth and severe small-for-gestational age birth weight among infants of immigrant mothers in Ontario originating from the Philippines and East Asia: a population-based study
  1. Emily Bartsch1,
  2. Alison L Park2,
  3. Jennifer Jairam3,
  4. Joel G Ray4
  1. 1 Faculty of Medicine, University of Toronto, Toronto, Canada
  2. 2 Institute for Clinical Evaluative Sciences Toronto, Toronto, Canada
  3. 3 Dalla Lana School of Public Health, University of Toronto, Toronto, Canada
  4. 4 Departments of Medicine, Health Policy Management and Evaluation, and Obstetrics and Gynecology St Michael's Hospital, University of Toronto, Toronto, Canada
  1. Correspondence to Dr Joel G Ray; RayJ{at}


Objectives Women from the Philippines form one of the largest immigrant groups to North America. Their newborns experience higher rates of preterm birth (PTB), and separately, small-for-gestational age (SGA) birth weight, compared with other East Asians. It is not known if Filipino women are at elevated risk of concomitant PTB and severe SGA (PTB–SGA), a pathological state likely reflective of placental dysfunction and neonatal morbidity.

Methods We conducted a population-based study of all singleton or twin live births in Ontario, from 2002 to 2011, among immigrant mothers from the Philippines (n=27 946), Vietnam (n=15 297), Hong Kong (n=5618), South Korea (n=5148) and China (n=42 517). We used modified Poisson regression to generate relative risks (RR) of PTB-SGA, defined as a birth <37 weeks’ gestation and a birth weight <5th percentile. RRs were adjusted for maternal age, parity, marital status, income quintile, infant sex and twin births.

Results Relative to mothers from China (2.3 per 1000), the rate of PTB–SGA was significantly higher among infants of mothers from the Philippines (6.5 per 1000; RR 2.91, 95% CI 2.27 to 3.73), and those from Vietnam (3.7 per 1000; RR 1.68, 95% CI 1.21 to 2.34). The RR of PTB–SGA was not higher for infants of mothers from Hong Kong or South Korea.

Interpretation Among infants born to immigrant women from five East Asian birthplaces, the risk of PTB–SGA was highest among those from the Philippines. These women and their fetuses may require additional monitoring and interventions.

  • preterm birth
  • small for gestational age birthweight
  • ethnicity
  • race
  • immigrant
  • East Asia
  • Philippines
  • Filipina
  • Vietnam

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  • Contributors EB and JR contributed to the study concept, analysis and interpretation of the data, drafting of manuscript, manuscript revision and approval of final version. AP contributed to the analysis and interpretation of the data, drafting of manuscript, manuscript revision and approval of final version. JJ contributed to the interpretation of the data and approval of final version.

  • Funding This work was supported by a grant from the Canadian Institutes of Health Research (CIHR). JGR holds a Canadian Institutes for Health Research Chair in Reproductive and Child Health Services and Policy Research, cofunded by the SickKids Foundation.

  • Competing interests None declared.

  • Ethics approval Ethics approval was granted by the Research Ethics Board of St Michael’s Hospital in Toronto, Ontario, Canada.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement Data are not available for public access.