Type 1 diabetes diagnosed during pregnancy - an unusual although important challenge: case series and review of literature

Amelia Caretto¹Erika Pedone¹Andrea Laurenzi^1,2Filippo Bolamperti²Caterina Cellai¹Federica Pasi³Serena Girardelli³Maria Teresa Castiglioni³Nicoletta Dozio⁴Marina Scavini^1*

• ¹Diabetes Research Institute, IRCCS San Raffaele Scientific Institute, Milan,, Milan, Italy
• ²Vita-Salute San Raffaele University, Milan, Italy, Milan, Italy
• ³Department of Obstetrics and Gynaecology, IRCCS San Raffaele Scientific Institute, Milan, Italy, Milan, Italy
• ⁴Azienda Socio-Sanitaria Territoriale (ASST) della Brianza, Vimercate, Italy, Vimercate, Italy

Hyperglycaemia diagnosed during pregnancy is most commonly due to gestational diabetes (GDM), while a minority of cases are attributable to previously unrecognized type 2 diabetes or, more rarely, type 1 diabetes (T1DM). Although T1DM has traditionally been associated with onset during childhood or adolescence, recent evidence shows that nearly forty percent of new T1DM cases occurs after age 30 years, coinciding with the age many women starting a pregnancy in Europe. This highlights the importance of considering T1DM in the differential diagnosis of Hyperglycaemia in pregnancy, given the relevant implications for management and outcomes of these pregnancies. Diabetes-related autoantibodies have been detected in pregnancies complicated by GDM, with prevalence varying widely (from less than 1% up to 18%), depending on population risk, assay, and antibody type. The most frequently found autoantibodies in GDM are islet cell antibodies (ICA) and anti-glutamic acid decarboxylase antibodies (GADA), while the presence of multiple autoantibodies is much rarer. Women with Hyperglycaemia and diabetes-related autoimmunity display a peculiar clinical picture: they usually have a normal pre-pregnancy BMI, low insulin resistance, and require insulin therapy more often than antibody-negative patients with Hyperglycaemia. They are typically younger and are likely to have a family history of diabetes or other autoimmune diseases. Importantly, the presence and especially the number of positive autoantibodies is associated with an increased risk of progressing to T1DM after pregnancy. Thus, identifying autoimmune markers of beta-cell damage in pregnant women with Hyperglycaemia is critical for prognosis and tailored management and follow up.