Risk factors for gestational diabetes mellitus and postpartum glucose intolerance: a retrospective study from a hospital specializing in infertility treatment

Gestational diabetes mellitus (GDM) is one of the most common complications of pregnancy and is associated with adverse outcomes for both mother and child as well as long-term maternal risk of type 2 diabetes. This study aimed to identify risk factors for the development of GDM and predictors of postpartum glucose intolerance. We conducted a single-center retrospective study at Sanno Hospital, Tokyo, including 11,694 pregnant women between 2015 and 2024. A total of 3177 women underwent a 75-g oral glucose tolerance test (OGTT) between 24 and 28 gestational weeks, and 1,025 were diagnosed with GDM (32.3%). The median maternal age at GDM diagnosis was 36 years, the mean prepregnancy body mass index (BMI) was 20.2 kg/m², and the postpartum OGTT was performed at 6-12 weeks after delivery. As a result, women with GDM were more likely to have advanced maternal age, history of GDM, family history of diabetes, higher prepregnancy BMI, elevated hemoglobin A1c levels, higher 50-g glucose challenge test (GCT) results, and higher OGTT values at GDM diagnosis. Infertility treatment itself was not a risk factor, though age and obesity in this population likely contribute. Prepregnancy obesity had a stronger impact on GDM risk than maternal age, and combining both factors markedly increased risk. GDM was associated with a higher rate of large-for-gestational-age infants and neonatal hypoglycemia. Postpartum follow-up showed that 65.6% of women returned to normal glucose tolerance, 31.4% developed impaired glucose tolerance, and 3.0% developed diabetes mellitus. History of GDM, family history of diabetes, multiple positive points on 75-g OGTT, and 2-h 75-g OGTT results at GDM diagnosis were risk factors for postpartum glucose intolerance. The 50-g GCT results could significantly predict the risk of postpartum insulin deficiency. In conclusion, history of infertility treatment was not a risk factor for GDM; however, other factors such as prepregnacy BMI were consistent with previous report findings. These findings highlight the importance of prepregnancy weight management and postpartum monitoring, and emphasize the need for lifelong follow-up in women with GDM. A multidisciplinary approach from preconception through postpartum is recommended.