The prevalence of gestational diabetes mellitus (GDM) ranges from 1 to 14% of all pregnancies, depending on the population studied and the diagnostic test and its glycemic cutoff, and it mirrors the prevalence of type 2 diabetes (1). The prevalence of GDM in Italy was reported to be 2.3–10% (2).

Sardinia has, with Finland, the highest prevalence in the world of type 1 diabetes and type 1 diabetes–related autoimmune disease (3), while the prevalence of type 2 diabetes is similar to that of other, not high-risk, populations. Its prevalence of GDM is still unknown.

Aiming to verify the prevalence of GDM in a large group of Sardinian women, we studied 1,103 pregnant volunteers of mean age 31 ± 5 years (range 16–46) and BMI 22.5 ± 3.8 kg/m2 (12.7–47.2) who gave consent to take part in an extended, universal screening procedure, at 16–18, 24–26, and 30–32 weeks of gestations. This protocol was chosen, together with a low glycemic threshold (130 mg/dl) for the oral glucose tolerance test, to avoid undiagnosed cases of GDM. Oral glucose tolerance test and diagnosis of GDM were performed according to the American Diabetes Association (4).

We showed a very high (247/1,103; 22.3%) prevalence of GDM, of which 28.4% was diagnosed at 16–18 weeks (prevalence 6.6%), 25.9% at 24–26 weeks (5.8%; not significant vs. 16–18 weeks), and 44.5% at 30–32 weeks (9.9%; P < 0.01 vs. 20–24 weeks and P < 0.02 vs. 16–18 weeks). The 130- mg/dl threshold allowed us to detect 12.8% more GDM cases compared with the 140 mg/dl threshold. The difference in prevalence of GDM between our group and others, particularly other Italian regions, is only partially explainable by our extended screening procedure. Furthermore, it is in contrast with the prevalence of type 2 diabetes in Sardinia. Considering the genetic and immunological characteristics of the Sardinian population, we postulate that a greater proportion of our GDM cases than that reported by others (5) can have autoimmune origin and thus be associated with the high type 1 prevalence in our island. This hypothesis is strengthened by the low prevalence of obesity (4.9%) and the relatively low BMI of our patients. An autoantibody panel is currently under investigation in our laboratory.

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