Gestational diabetes mellitus by maternal country of birth and length of residence in immigrant women in Norway

Aims Immigrant women are at higher risk for gestational diabetes mellitus (GDM) than non-immigrant women. This study described the prevalence of GDM in immigrant women by maternal country of birth and examined the associations between immigrants' length of residence in Norway and GDM. Methods This Norwegian national population-based study included 192,892 pregnancies to immigrant and 1,116,954 pregnancies to non-immigrant women giving birth during the period 1990-2013. Associations were reported as odds ratios (ORs) with 95% confidence intervals (CIs) using logistic regression models, adjusted for year of delivery, maternal age, marital status, health region, parity, education and income. Results The prevalence and adjusted OR [CI] for GDM were substantially higher in immigrant women from Bangladesh (7.4%, OR 8.38 [5.41, 12.97]), Sri Lanka (6.3%, OR 7.60 [6.71, 8.60]), Pakistan (4.3%, OR 5.47 [4.90, 6.11]), India (4.4%, OR 5.18 [4.30, 6.24]) and Morocco (4.3%, OR 4.35 [3.63, 5.20]) compared to non-immigrants (prevalence 0.8%). Overall, GDM prevalence increased from 1.3% (OR 1.25 [1.14, 1.36]) to 3.3% (OR 2.55 [2.39, 2.71]) after 9 years of residence in immigrants compared to non-immigrant women. This association was particularly strong for women from South Asia. Conclusions Gestational diabetes mellitus prevalence varied substantially between countries of maternal birth and was particularly high in immigrants from Asian countries. GDM appeared to increase with longer length of residence in certain immigrant groups.