Objective：To observe the ultrastructure of placental trophoblast cells of pregnant women with gestational diabetes mellitus（GDM），and to investigate the role of ferroptosis in the occurrence and development of GDM. Methods：Pregnant women who delivered at the Changzhou Maternal and Child Health Hospital from September 2020 to December 2022 were enrolled and underwent an oral glucose tolerance test at 24-28 weeks of gestation. Pregnant women diagnosed with GDM were selected as the research subjects and divided into four groups：diet-controlled glucose satisfaction group（G1 group），oral metformin-controlled glucose group（G2 group）， insulin-controlled glucose group（G3 group），and unsatisfactory glucose control but refused to use medication group（G4 group），each with 30 cases. Normal healthy pregnant women were included as the control group（N group）. The ultrastructure of placental trophoblast cells in each group was observed by transmission electron microscopy. The placental iron deposition was detected by Prussian blue staining. The localizations and expressions of Acyl-CoA synthetase long chain family member 4（ACSL4）and glutathione peroxidase 4（GPX4）in the syncytiotrophoblast layer were detected by immunohistochemistry. The protein expressions and the mRNA transcription levels of ACSL4 and GPX4 in the placenta were detected by Western blot and qRT -PCR，respectively. Results：Under transmission electron microscopy，varying degrees of mitochondrial morphological changes were observed in the placentas of GDM women in the G1，G2，G3，and G4 groups，with G1，G2，and G3 groups showing milder mitochondrial changes，and the G4 group exhibiting typical ferroptosis with shrunken mitochondria. Prussian blue staining demonstrated iron particles in all five groups，with a significant increase in iron particles in the G1，G2，G3，and G4 groups compared to the N group and a significant decrease in iron particles in the G1，G2 and G3 groups compared to the G4 group. Western blot results showed an increase in ACSL4 protein expression and a decrease in GPX4 protein expression in the placenta of G1，G2，G3，and G4 groups compared to the N group，while qRT-PCR results showed no significant difference in ACSL4 and GPX4 mRNA transcription levels between the groups. Conclusion：Ferroptosis exists in placental trophoblast cells of pregnant women with GDM，and it is correlated with the severity of the disease and medication. Abnormal expression of ACSL4 and GPX4 in the placenta of GDM pregnant women. Metformin and insulin have a role in improving ferroptosis of placental trophoblast cells.