Randomized clinical trials, full-text articles available for reading and data extraction, patients with current gestational diabetes mellitus; comparison between two groups of patients, with one group using metformin and the other insulin therapy, and studies that present at least one of the following outcomes: birth weight, mode of delivery, need for NICU admission, gestational age at birth, neonatal hypoglycemia, neonates large for gestational age at birth, progression to preeclampsia, and Apgar score at 5 minutes of life. Here, INS is linked to gestational diabetes.