Association between maternal country of birth and preterm birth: A population-based register study of 910,752 deliveries

Scand J Public Health. 2021 Dec;49(8):904-913. doi: 10.1177/1403494821992894. Epub 2021 Feb 15.

Abstract

Aims: The aim of this study was to analyse associations between maternal country of birth and preterm birth among women giving birth in Norway. Methods: A population-based register study was conducted employing official national databases in Norway. All singleton births, with neonates without major anomalies, between 1999 and 2014 were included (N=910,752). We estimated odds ratios (ORs) for extremely preterm birth (<28 weeks gestation), very preterm birth (28-33 weeks gestation) and late preterm birth (34-36 weeks gestation) by maternal country of birth. We conducted multivariable regression analyses, adjusting for maternal, obstetric and socio-economic confounders. Results: For extremely preterm births (0.4% of the study population), women with an unknown country of birth (adjusted OR (aOR)=3.09; 95% confidence interval (CI) 2.26-4.22) and women born in sub-Saharan Africa (aOR=1.66; CI 1.40-1.96) had the highest ORs compared to Norwegian-born women. For very preterm births (1.2% of the study population), women with an unknown country of birth (aOR=1.72; CI 1.36-2.18) and women born in South Asia (aOR=1.48; CI 1.31-1.66) had the highest ORs. For late preterm births (3.8% of the study population), women born in East Asia Pacific/Oceania (aOR=1.33; CI 1.25-1.41) and South Asia (aOR=1.30; CI 1.21-1.39) had the highest ORs. Conclusions: After adjusting for maternal, obstetric and socio-economic risk factors, maternal country of birth remained significantly associated with preterm birth. Women with an unknown country of birth and women born in sub-Saharan Africa were found to be at increased risk of extremely preterm birth.

Keywords: Epidemiology; extremely preterm birth; immigrant; late preterm birth; medical birth registry; preterm birth; socio-economic factors; very preterm birth.

MeSH terms

  • Female
  • Gestational Age
  • Humans
  • Infant, Newborn
  • Odds Ratio
  • Parturition
  • Pregnancy
  • Premature Birth* / epidemiology
  • Risk Factors