Background: In the second or third trimester of pregnancy, gestational diabetes mellitus (GDM) can be characterized as glucose intolerance that was not overt prior to gestation. It can have long-term health effects, even if most GDMs go away on their own after delivery. It involves a higher risk for mothers to develop cardiovascular problems or type 2 diabetes mellitus (T2DM), and the child's propensity for obesity, cardiovascular disease, or T2DM.In addition to the liver, other metabolically active tissues such as fat, skeletal muscle, and the pancreas express the hepatokine FGF-21. T2DM can be predicted by a high level of FGF-21. T2DM and GDM are thought to share comparable pathogenesis, but the link between FGF-21 and GDM remains vague. The aim of the study to assess the correlation of FGF-21 with fetal and maternal complications among cases who had GDM. Patients and methods: There were 50 women diagnosed with GDM at 24-28 weeks of gestation and 50 healthy women recruited from the Diabetes and Obstetrics outpatient clinic to participate in this case-control research. Results: GDM patients had greater concentrations of FGF-21 compared to control group (p-value <0.01). Fasting blood glucose, 2-hour postprandial glucose, and haemoglobin A1C all had a significant correlation with serum FGF-21 in our research. Moreover, serum FGF-21 was correlated with the incidence of maternal hypertension in the studied groups (p-value 0.011), while the correlation of FGF-21 with the incidence of fetal complications whether fetal macrosomia, respiratory distress, or neonatal hypoglycemia was not significant. Conclusion: : FGF-21 levels are elevated in patients with GDM. Pregnant women who had greater levels of FGF-21 in their blood were shown to have higher blood pressure readings in this study. Maternal and fetal outcomes should be better linked to FGF-21 levels during pregnancy through additional research.