Mild periconceptional hyperglycemia: predictor of adverse fetomaternal outcomes in gestational diabetes?

To clarify whether mild first trimester hyperglycaemia (characteristic of early-onset GDM) is associated with higher incidence of congenital malformations and other adverse fetomaternal outcomes compared to women with second trimester hyperglycaemia (later-onset GDM).

We analyzed the Portuguese National GDM database, containing data collected between 2011 and 2017. Two study groups were defined: Group 1-Women with GDM diagnosed during the first trimester (with fasting glycemia ≥ 92 and < 126 mg/dL); Group 2-Women with GDM diagnosed after the first 12 weeks of gestation, with either fasting glycemia or oral glucose tolerance test, according to the International Association of Pregnancy and Diabetes Study Group criteria. The fetomaternal characteristics of each group were compared.

A total of 18.518 pregnant women diagnosed with GDM were included which 34.4% of them belonged to Group 1. Pregnant women from this group were significantly younger and had a higher median BMI than the women from the other group. Overall, there was no significant differences in maternal morbidity parameters between groups. Non-evolutive pregnancies were significantly more frequent along the present gestation in the group 1 (1.1% vs. 0.1%, p < 0.001), as was fetal death (0.6% vs. 0.2%, p < 0.001). Congenital malformations did not differ significantly between groups (3.2% vs. 2.8%, p = 0.155).

The mild near conceptional hyperglycaemic state characteristic of an early-onset GDM seems to be associated with an increased prevalence of non-evolutive pregnancies and foetal deaths when compared to later-onset GDM.