Background: Gestational diabetes mellitus (GDM) affects roughly 14% of pregnancies, its prevalence is increasing, and it is associated with a significant risk of complications for both mother and offspring. A high proportion of women with GDM can be detected early in pregnancy. In Italy, early GDM screening occurs in a selective way, as it is performed only in the presence of important risk factors. It remains to be elucidated not only how and when to diagnose early GDM but especially whether to treat it. This study aimed to compare the characteristics and complications of early vs late GDM as assessed and treated in a real-world setting, according to the Italian guidelines of the Istituto Superiore di Sanità. Methods: We conducted a retrospective cohort study in women with GDM delivering singletons between 2017 and 2021. Results: Women with early GDM had higher BMI and a higher proportion of Middle Eastern or African women. Early GDM was independently associated with the use of insulin (p < 0.001). It required also higher doses of insulin, possibly due to the higher BMI. Early GDM was also independently associated with higher post-prandial (after dinner) glucose levels during the 3° trimester (p = 0.04). Nevertheless, early GDM women achieved glucose targets and put on less weight during gestation. Early GDM was independently associated with preeclampsia (p = 0.05). Otherwise, there were no other differences between early and late GDM in terms of pregnancy complications. After delivery, early GDM was independently associated with abnormal glucose tolerance. Conclusions: Early GDM women exhibited more severe GDM features. However, after achieving recommended glucose and body weight targets, there were no substantial differences between early and late GDM in terms of pregnancy complications apart from preeclampsia. These data support diagnosis and treatment of women with early GDM.
