Objective:To compare serum Xenopsin-Related Peptide-1 (XP-1) levels in pregnant women diagnosed with gestational diabetes mellitus (GDM) versus healthy pregnant controls.Methods:This prospective cohort study included pregnant women attending the Gynecology and Obstetrics outpatient clinic at Health Sciences University (SBU) Ümraniye Training and Research Hospital between April 1, 2023, and October 1, 2023. Pregnacies were between 24–28 weeks of gestation, aged 18–45 years, with singleton pregnancies, and without chronic systemic diseases. Following a 75 g oral glucose tolerance test (OGTT), 44 women diagnosed with GDM, while 44 women without GDM classified as controls. Serum XP-1 levels were assessed and compared between the groups. Blood samples were collected into anticoagulant-free tubes, centrifuged (2000–3000 rpm, 10 minutes), and serum samples were stored at -80°C until analysis. On the day of measurement, thawed samples were evaluated using the ELISA method with a commercial kit.Results:Pregnancies in the GDM group were significantly older than those in the control group (p = 0.001). However, no statistically significant differences were observed between the groups regarding BMI at blood collection, pre-pregnancy BMI, weight gain, molecular XP-1 levels, or history of GDM (p > 0.05). Serum XP-1 levels ranged from 0.2 to 8.63 ng/mL, with a mean of 2.52 ± 1.81 ng/mL. XP-1 levels showed no significant association with treatment agents, BMI, pre-pregnancy BMI, weight gain, abdominal circumference (AC), or estimated fetal weight (EFW) at the time of blood collection (p > 0.05).Conclusion:We found no significant association between serum XP-1 levels and GDM. Older maternal age was more prevalent in the GDM group. Further multidisciplinary, prospective studies are recommended to explore the potential role of XP-1 in pregnancy and GDM.