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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.

Predictors for glucose intolerance postpartum were evaluated in women with gestational diabetes mellitus (GDM) based on the 2013 World Health Organization (WHO) criteria. 1841 women were tested for GDM in a prospective cohort study. A postpartum 75g oral glucose tolerance test (OGTT) was performed in women with GDM at 14 ± 4.1 weeks. Of all 231 mothers with GDM, 83.1% (192) had a postpartum OGTT of which 18.2% (35) had glucose intolerance. Women with glucose intolerance were more often of Asian origin [15.1% vs. 3.7%, OR 4.64 (1.26⁻17.12)], had more often a recurrent history of GDM [41.7% vs. 26.7%, OR 3.68 (1.37⁻9.87)], higher fasting glycaemia (FPG) [5.1 (4.5⁻5.3) vs. 4.6 (4.3⁻5.1) mmol/L, OR 1.05 (1.01⁻1.09)], higher HbA1c [33 (31⁻36) vs. 32 (30⁻33) mmol/mol, OR 4.89 (1.61⁻14.82)], and higher triglycerides [2.2 (1.9⁻2.8) vs. 2.0 (1.6⁻2.5) mmol/L, OR 1.00 (1.00⁻1.01)]. Sensitivity of glucose challenge test (GCT) ≥7.2 mmol/l for glucose intolerance postpartum was 80% (63.1%⁻91.6%). The area under the curve to predict glucose intolerance was 0.76 (0.65⁻0.87) for FPG, 0.54 (0.43⁻0.65) for HbA1c and 0.75 (0.64⁻0.86) for both combined. In conclusion, nearly one-fifth of women with GDM have glucose intolerance postpartum. A GCT ≥7.2 mmol/L identifies a high risk population for glucose intolerance postpartum.

This study determines if a modified two-step screening strategy with a glucose challenge test (GCT) ≥ 7.2 mmol/L and clinical risk factors improves the diagnostic accuracy for gestational diabetes mellitus (GDM), based on 2013 WHO criteria, while limiting the number of oral glucose tolerance tests (OGTT). This was a prospective multicentric cohort study with 1811 participants receiving both GCT and 75 g OGTT in pregnancy. Participants and health care providers were blinded for GCT. Characteristics were analyzed across four glucose tolerance groups: abnormal (≥7.2 mmol/L), GCT GDM ( n = 165), normal GCT GDM ( n = 63), abnormal GCT normal glucose tolerant (NGT) ( n = 472); normal GCT NGT ( n = 1113). Compared to normal GCT NGT women, normal GCT GDM women had increased rates of obesity (23.8% vs. 10.5%, p < 0.001), ethnic minority background (19.3% vs. 8.2%, p < 0.001) and a history of GDM (13.8% vs. 4.6%, p = 0.03). By combined screening of GCT ≥ 7.2 mmol/L with these risk factors, sensitivity increased to respectively, 74.1⁻78.1% using one risk factor, and to 82.9% using any of these risk factors with a specificity of 57.5%. By using a modified two-step screening strategy, the number of women needing both a GCT and OGTT would be reduced to 25.5%, and 52.6% of all OGTTs could be avoided, compared to a universal one-step approach.