Our objective was to compare, in a Caucasian population, the perinatal outcomes of pregnancies complicated by pregestational diabetes diagnosed in the first-trimester of pregnancy with those of pregnancies complicated by gestational diabetes.

A retrospective evaluation of maternal and neonatal outcomes was performed for all consecutive pregnancies complicated by gestational or pregestational diabetes that happened between 2005 and 2011. Pregestational diabetes was diagnosed for the first time in pregnancy if the first-trimester fasting glycaemia was≥126mg/dL. Gestational diabetes was diagnosed according to Carpenter–Coustan criteria until May 2010, and then according to the International Association of Diabetes and Pregnancy Study Groups (IADPSG) panel criteria modified by the American Diabetes Association. A specific diet, self-monitoring of blood glucose and, if required, insulin treatment were prescribed.

Overall, 411 pregnant women were considered eligible for the study (379 with gestational diabetes and 32 with pregestational diabetes). Women with pregestational vs. gestational diabetes were diagnosed earlier in pregnancy (11.6±1.0 weeks vs. 25.9±1.7 weeks; P=0.0001), had a higher mean first-trimester fasting glycaemic level (129.5±3.6mg/dL vs. 81.6±10.5mg/dL; P=0.0001), more often had a family history of diabetes (46.9% vs. 25.9%; P=0.02) and more often needed insulin treatment (78.1% vs. 14.0%; P=0.0001). Furthermore, a higher rate of fetal malformations in women with pregestational diabetes was detected (9.4% vs. 1.6%, P=0.02). No other differences in neonatal outcomes were identified.

In a Caucasian population, the prevalence of fetal malformations and insulin requirements with pregestational diabetes first diagnosed in pregnancy were significantly higher compared with women with gestational diabetes. In any case, glucose impairment in pregnancy needs to be diagnosed in a timely fashion and appropriately treated to improve both maternal and fetal outcomes.