To evaluate the effectiveness of the different insulin therapies on obstetrics-fetal outcomes in women with pregestational diabetes mellitus. We enrolled 147 pregnant women with pre-existing type 1 or 2 diabetes mellitus. Clinical and biochemical parameters were analysed in relation to obstetric and fetal outcomes. 14.2% received treatment with Neutral Protamine Hagedorn insulin and short-acting insulin analogues; 19% with premixed human insulin; 40.1% with insulin glargine and lispro, 6.2% with detemir and aspart and 20% with continuous subcutaneous insulin infusion. All 5 types of treatment achieved a reduction of the mean HbA1c during pregnancy (p = 0.01). Pre-pregnancy care was carried out for 48% of patients. We found no statistically significant differences between the different insulin therapies and the obstetric-fetal outcomes. In conclusión, the different insulin therapies used in patients with pregestational diabetes mellitus does not seem to affect obstetric-fetal outcomes.