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

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.

Risk of preterm birth in relation to history of preterm birth: a population‐based registry study of 213 335 women in Norway

“…European countries were divided into European Economic Association (EEA) (including Switzerland) and non‐EEA groups. Due to there being few women from Transcaucasia and Central Asia, they were included in the non‐EEA group 19 …”

“…Due to there being few women from Transcaucasia and Central Asia, they were included in the non-EEA group. 19 Information on education from SSB served as a proxy for socio-economic status. The eight levels of education in the 2011 International Standard Classification of Education were merged into four groups according to years of highest completed education.…”

Different pathways for preterm birth between singleton and twin pregnancies: a population‐based registry study of 481 176 nulliparous women

“…The maternal country of birth was categorised using ten regions, based on the definitions used by the World Bank 10 . Women born in Norway served as the reference group.…”

“…The maternal country of birth was categorised using ten regions, based on the definitions used by the World Bank. 10 Women born in Norway served as the reference group. European countries were divided into European Economic Association (EEA, including Switzerland) and non‐EEA countries.…”

Prevalence of preterm birth in Scandinavian countries: a systematic review and meta-analysis

“…Sweden had the highest number of eligible studies (44 studies), 14, followed by Denmark (29 studies), 15,33,52, Norway (26 studies), 16,33,52,54,59,74,84,[90][91][92][93][94][95][96][97][98][99][100][101][102][103][104][105][106][107][108] Finland (19 studies), 16,33,52,71,[108][109][110][111][112][113][114][115][116][117][118][119][120][121][122] and Iceland (four studies). 33,[123]…”