Perinatal and long‐term implications of diagnosing gestational diabetes mellitus using only fasting and one‐hour post‐load glucose concentrations: Secondary analysis of the <scp>GEMS</scp> trial and its five‐year follow‐up

INTRODUCTION: The proposed revised diagnostic criteria for gestational diabetes (GDM) in New Zealand include a fasting plasma glucose (FPG) concentration ≥5.3 mmol/L and 1-h post-load glucose (PLG) concentration ≥10.6 mmol/L on a 75 g oral glucose tolerance test (OGTT), but no 2-h PLG. This study evaluates the impact of GDM diagnosis based on FPG and/or 1-h PLG abnormalities on perinatal and long-term outcomes. MATERIAL AND METHODS: This secondary analysis of data from GEMS, a multicentre, randomized trial and its follow-up, included women and their children who met the proposed revised GDM criteria and received treatment. Participants were classified into three groups: (1) both group: elevated FPG and 1-h PLG, (2) fasting group: elevated FPG alone, and (3) one-hour group: elevated 1-h PLG alone. Between-group pairwise comparisons were made using log-binomial and normal-identity regressions. RESULTS: Of 217 eligible women-child pairs, 85 (39.2%) were in the fasting group, 61 (28.1%) in the both group, and 71 (32.7%) in the one-hour group. Women in the fasting and both groups, compared with the one-hour group, were more likely to be overweight or obese both at the first antenatal visit and five-year follow-up, more likely to have required pharmacotherapy for GDM (85.9% and 88.5% vs. 69.0%; p < 0.0001), and had higher rates of type 2 diabetes/prediabetes at 5 years (50.0% and 48.8% vs. 28.3%; p = 0.03). Their infants were born earlier (38.1 and 38.0 vs. 38.6 weeks; p = 0.02) with higher birthweight z-scores (0.2 and 0.1 vs. -0.2; p = 0.03). Infants in the fasting group, compared with infants in the one-hour group, had higher rates of being large-for-gestational age and neonatal intensive care unit admission. At 5 years, children in the fasting group, compared with those in the one-hour group, had higher mean z-scores in weight and height, and were more likely to have an abnormal developmental screening questionnaire score (24.4% vs. 5.1%; p = 0.04). CONCLUSIONS: Women diagnosed with GDM based on an elevated FPG, compared with those with only an elevated 1-h PLG, may have had increased diabetes risks at five-year follow-up, while their children may have greater infant health risks and greater growth at 5 years.