The incidence of gestational diabetes mellitus (GDM) is increasing worldwide. This has a significant effect on the health of the mother and offspring. There is no doubt that screening for GDM between 24 and 28 weeks is important to reduce the risk of adverse pregnancy outcomes. However, there is no consensus about diagnosis and treatment of GDM in early pregnancy. In this narrative review on the current evidence on screening for GDM in early pregnancy, we included 37 cohort studies and eight randomized controlled trials (RCTs). Observational studies have shown that a high proportion (15–70%) of women with GDM can be detected early in pregnancy depending on the setting, criteria used and screening strategy. Data from observational studies on the potential benefit of screening and treatment of GDM in early pregnancy show conflicting results. In addition, there is substantial heterogeneity in age and BMI across the different study populations. Smaller RCTs could not show benefit but several large RCTs are ongoing. RCTs are also necessary to determine the appropriate cut-off for HbA1c in pregnancy as there is limited evidence showing that an HbA1c ≥6.5% has a low sensitivity to detect overt diabetes in early pregnancy.

Aim: To determine the association between thyroid function and the risk of developing gestational diabetes mellitus (GDM) and adverse pregnancy outcomes. Methods: This case–control study was a sub-analysis of the BEDIP-N study, in which 199 GDM women were matched for age and body mass index with 398 controls. Thyroid-stimulating hormone (TSH), free thyroxine (fT4), free triiodothyronine (fT3), and thyroid peroxidase (TPO) antibodies were measured at 6–14 weeks and 26–28 weeks during pregnancy. TSH and fT4 were also measured in early postpartum in GDM women. Results: The fT3-to-fT4 ratio at 26–28 weeks was positively associated with GDM risk with an adjusted odds ratio (aOR for smoking, education, parity, ethnicity, gestational weight gain, and (family) history of diabetes or GDM) of 2.12 (95% CI 1.07; 4.23), comparing the highest with the lowest tertile. Higher fT3 levels and a higher fT3-to-fT4 ratio were associated with a less favorable metabolic profile with higher BMI and more insulin resistance during pregnancy and postpartum. Women in the upper fT3 tertile and the upper fT3-to-fT4 ratio had a higher rate of preeclampsia [4.6% (10) vs. 1.0% (2), p = 0.040, and 4.4% (9) vs. 0.5% (1), p = 0.020], gestational hypertension [8.3% (18) vs. 3.1% (6), p = 0.034 and 8.9% (18) vs. 2.0% (4), p = 0.003], and caesarean sections [29.4% (63) vs. 16.1% (31), p = 0.002 and 32.2% (65) vs. 12.7% (25), p < 0.001]. Conclusion: A higher fT3-to-fT4 ratio late into pregnancy was associated with GDM, adverse pregnancy outcomes, and an adverse metabolic profile in early postpartum.

AimsTo determine the preferred method of screening for gestational diabetes mellitus (GDM).Methods1804 women from a prospective study (NCT02036619) received a glucose challenge test (GCT) and 75g oral glucose tolerance test (OGTT) between 24-28 weeks. Tolerance of screening tests and preference for screening strategy (two-step screening strategy with GCT compared to one-step screening strategy with OGTT) were evaluated by a self-designed questionnaire at the time of the GCT and OGTT.ResultsCompared to women who preferred one-step screening [26.2% (472)], women who preferred two-step screening [46.3% (834)] were less often from a minor ethnic background [6.0% (50) vs. 10.7% (50), p=0.003], had less often a previous history of GDM [7.3% (29) vs. 13.8% (32), p=0.008], were less often overweight or obese [respectively 23.1% (50) vs. 24.8% (116), p&lt;0.001 and 7.9% (66) vs. 18.2% (85), p&lt;0.001], were less insulin resistant in early pregnancy (HOMA-IR 8.9 (6.4-12.3) vs. 9.9 (7.2-14.2), p&lt;0.001], and pregnancy outcomes were similar except for fewer labor inductions and emergency cesarean sections [respectively 26.6% (198) vs. 32.5% (137), p=0.031 and 8.2% (68) vs. 13.0% (61), p=0.005]. Women who preferred two-step screening had more often complaints of the OGTT compared to women who preferred one-step screening [50.4% (420) vs. 40.3% (190), p&lt;0.001].ConclusionsA two-step GDM screening involving a GCT and subsequent OGTT is the preferred GDM screening strategy. Women with a more adverse metabolic profile preferred one-step screening with OGTT while women preferring two-step screening had a better metabolic profile and more discomfort of the OGTT. The preference for the GDM screening method is in line with the recommended Flemish modified two-step screening method, in which women at higher risk for GDM are recommended a one-step screening strategy with an OGTT, while women without these risk factors, are offered a two-step screening strategy with GCT.Clinical Trial RegistrationNCT02036619 https://clinicaltrials.gov/ct2/show/NCT02036619

The Belgian Diabetes in Pregnancy follow-up study (BEDIP-FUS) aims to investigate the impact of body mass index (BMI), adiposity and different degrees of glucose intolerance on the metabolic profile and future risk for type 2 diabetes (T2D) in women and offspring five years after delivery in the BEDIP study. The BEDIP study was a prospective cohort study to evaluate different screening strategies for gestational diabetes (GDM) based on the 2013 WHO criteria. The aim of the BEDIP-FUS is to recruit 375 women–offspring pairs, stratified according to three different subgroups based on the antenatal result of the glucose challenge test (GCT) and oral glucose tolerance test (OGTT) during the BEDIP pregnancy. The follow-up visit consists of a 75 g OGTT, anthropometric measurements and questionnaires for the mothers, and a fasting blood sample with anthropometric measurements for the child. Primary outcome for the mother is glucose intolerance defined by the American Diabetes Association criteria and for the offspring the BMI z-score. Recruitment began in January 2021. The BEDIP-FUS study will help to better individualize follow-up in women with different degrees of hyperglycemia in pregnancy and their offspring.

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