Multiple positive points during the 75 g oral glucose tolerance test are good predictors for early insulin therapy in gestational diabetes mellitus diagnosed before 24 gestational weeks.

Aims/introduction: This study evaluated the risk factors for insulin therapy before 24 gestational weeks (early insulin therapy) in pregnant women with gestational diabetes diagnosed before 24 gestational weeks (E-GDM).

Materials and methods: This study included 530 singleton mothers with E-GDM who underwent a 75 g oral glucose tolerance test (OGTT) in the first trimester at Keio University Hospital between January 2013 and December 2021. E-GDM can be classified according to its management into only diet therapy until delivery (Diet E-GDM), insulin therapy started before 24 gestational weeks (EarlyIns E-GDM), and insulin therapy started after 24 gestational weeks (LateIns E-GDM). We analyzed the risk factors for EarlyIns E-GDM.

Results: Patients with EarlyIns E-GDM had a significantly higher maternal age at delivery, pre-pregnancy BMI, first trimester hemoglobin A1c, 1 h plasma glucose levels (1 h-PG), and 2 h-PG, as well as a more pronounced initial increase and subsequent decrease, compared with those in the Diet E-GDM group. However, the Apgar scores at both 1 and 5 min were significantly lower in patients with EarlyIns E-GDM than in those with Diet E-GDM. The number of abnormal values in the OGTT showed the largest area under the receiver operating characteristic curve (AUC) for predicting EarlyIns E-GDM (0.83, 95% confidence interval [CI]: 0.79-0.86), followed by the 1 h-PG value (AUC: 0.81, 95% CI: 0.77-0.85). The initial increase showed the third largest AUC (0.78, 95% CI: 0.74-0.82).

Conclusions: Although further research is needed, our data suggest the importance of early insulin therapy in cases of E-GDM with multiple abnormal OGTT values, especially with high 1 h-PG levels and initial increase.