BackgroundBeing overweight is an important risk factor for Gestational Diabetes Mellitus (GDM), but the underlying mechanisms are not understood. Weight change between pregnancies has been suggested to be an independent mechanism behind GDM. We assessed the risk for GDM in second pregnancy by change in Body Mass Index (BMI) from first to second pregnancy and whether BMI and gestational weight gain modified the risk.Methods and findingsIn this observational cohort, we included 24,198 mothers and their 2 first pregnancies in data from the Medical Birth Registry of Norway (2006–2014). Weight change, defined as prepregnant BMI in second pregnancy minus prepregnant BMI in first pregnancy, was divided into 6 categories by units BMI (kilo/square meter). Relative risk (RR) estimates were obtained by general linear models for the binary family and adjusted for maternal age at second delivery, country of birth, education, smoking in pregnancy, interpregnancy interval, and year of second birth. Analyses were stratified by BMI (first pregnancy) and gestational weight gain (second pregnancy). Compared to women with stable BMI (−1 to 1), women who gained weight between pregnancies had higher risk of GDM—gaining 1 to 2 units: adjusted RR 2.0 (95% CI 1.5 to 2.7), 2 to 4 units: RR 2.6 (2.0 to 3.5), and ≥4 units: RR 5.4 (4.0 to 7.4). Risk increased significantly both for women with BMI below and above 25 at first pregnancy, although it increased more for the former group. A limitation in our study was the limited data on BMI in 2 pregnancies.ConclusionsThe risk of GDM increased with increasing weight gain from first to second pregnancy, and more strongly among women with BMI < 25 in first pregnancy. Our results suggest weight change as a metabolic mechanism behind the increased risk of GDM, thus weight change should be acknowledged as an independent factor for screening GDM in clinical guidelines. Promoting healthy weight from preconception through the postpartum period should be a target.

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.

Objective To estimate recurrence risk of gestational diabetes mellitus (GDM) by interpregnancy weight change. Design Population‐based cohort study. Setting and population Data from the Swedish (1992–2010) and the Norwegian (2006–2014) Medical Birth Registries on 2763 women with GDM in first pregnancy, registered with their first two singleton births and available information on height and weight. Methods Interpregnancy weight change (BMI in second pregnancy minus BMI in first pregnancy) was categorised in six groups by BMI units. Relative risks (RRs) of GDM recurrence were obtained by general linear models for the binary family and adjusted for confounders. Analyses were stratified by BMI in first pregnancy (<25 and ≥25 kg/m2). Main outcome measure GDM in second pregnancy. Results Among overweight/obese women (BMI ≥25), recurrence risk of GDM decreased in women who reduced their BMI by 1–2 units (relative risk [RR] 0.80, 95% CI 0.65–0.99) and >2 units (RR 0.72, 95% CI 0.59–0.89) and increased if BMI increased by ≥4 units (RR 1.26, 95% CI 1.05–1.51) compared wth women with stable BMI (−1 to 1 units). In normal weight women (BMI <25), risk of GDM recurrence increased if BMI increased by 2–4 units (RR 1.32, 95% CI 1.08–1.60) and ≥4 units (RR 1.61, 95% CI 1.28–2.02) compared with women with stable BMI. Conclusion Interpregnancy weight loss reduced risk of GDM recurrence in overweight/obese women. Weight gain between pregnancies increased recurrence risk for GDM in both normal and overweight/obese women. Our findings highlight the importance of weight management in the interconception window in women with a history of GDM. Tweetable abstract Interpregnancy weight loss reduces recurrence of gestational diabetes mellitus in overweight/obese women.