Aims: To study the evolution of mitochondrial-derived peptides (MDPs) and their relationship with changes in insulin sensitivity from the early stages of pregnancy.Methods: MDPs (humanin and MOTSc) were assessed in the first and second trimesters of gestation in 28 pregnant women with gestational diabetes mellitus (GDM) and a subgroup of 45 matched pregnant women without GDM. Insulin resistance (IR) was defined as a HOMA-IR index ≥70 percentile.Results: We observed a significant reduction in both humanin and MOTSc levels from the first to the second trimesters of pregnancy. After adjusting for BMI we did not find an association between low levels of humanin and the occurrence of a high HOMA-IR index (adjusted OR= 2.63 and 3.14, linear p-trend 0.260 and 0.175, respectively). Regarding MOTSc, an association was found only for the second trimester: adjusted OR=7.68 (95% CI 1.49-39.67), linear p-trend=0.012. No significant associations were observed in humanin change with insulin resistance throughout pregnancy, but changes in MOTSc levels were significantly associated with HOMA-IR index: adjusted OR 3.73 (95% CI 1.03-13.50).Conclusions: MOTSc levels, especially a strong decrease from the first to the second trimester of gestation, may be involved in increasing insulin resistance during early gestation.CLINICAL TRIAL REGISTRATIONNot applicable