Abstract Ghrelin is an orexigenic gastric peptide hormone implicated in pleiotropic functions, playing an important role in the regulation of food intake and homeostatic body weight regulation mediated through the growth hormone secretagogue receptor (GHSR). Recently, the liver and small intestine–derived peptide liver enriched antimicrobial peptide-2 (LEAP-2) was characterized to acts as an endogenous GHSR antagonist and blunts the orexigenic action of ghrelin. On the other hand, physiologic maternal weight gain during each trimester of pregnancy might be associated primarily with the developing fetus and the maternal energy requirements. This study aimed to determine serum LEAP-2 levels and Ghrelin/Leap-2 ratio in pregnant women at each trimester of gestation and three months postpartum. We conducted a nested study within an observational prospective cohort study. Twenty five healthy women were longitudinally studied during the first, second and third trimester of pregnancy and three months postpartum. Additionally, twenty healthy non – pregnant women were studied during the follicular a luteal phase of the menstrual cycle. Biochemical and hormonal laboratory measurements were performed during the early morning hours (07: 00-08: 00 hours) following an overnight fast (9: 00-10: 00 hours). Human serum Ghrelin (MBS283919) and LEAP-2 (MBS917663) levels were determined using the commercially available ELISA kits and the ratio between circulating Ghrelin and Leap-2 (Ghrelin/Leap-2) levels was calculated. The clinical and biochemical parameters in the studied population of pregnant women and non – pregnant women were described. In healthy pregnant women, circulating Ghrelin levels decreased significantly in the third trimester of gestation (p<0.05). Also, serum Ghrelin levels are markedly increased after delivery and reaching the levels from first trimester of pregnancy (p>0.05). Additionally, in healthy pregnant women, a significant decrease was observed in serum LEAP-2 concentrations from second to third trimesters of pregnancy (p<0.05). In addition, serum LEAP-2 levels were significantly increased after delivery and returned to the levels of the first trimester of gestation. The Ghrelin/Leap-2 ratio increases significantly during pregnancy and reaches its peak in the second and third trimester of gestation in healthy pregnant women (p<0.05). In conclusion, this study provides the first evidence that Ghrelin/Leap-2 ratio increase steadily during pregnancy reaching their peak in the second and third trimester of pregnancy. Additionally, the findings of this study suggest that Ghrelin/Leap-2 ratio might play an important role in maternal physiology adaptation of weight gain during pregnancy. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.