INS and gestational diabetes: The rapid-acting insulin analogues have the advantage of a more rapid onset of action than human insulin and the long-acting analogues are released more slowly, without a peak in activity, providing more stable blood levels for a longer duration.[9] There has been debate about the safety of oral antidiabetics such as metformin in pregnancy, but recent UK guidelines[17] and a meta-analysis[18] suggest that there is now evidence relating to the efficacy and safety of metformin use for the treatment of gestational diabetes.