Objective To explore the impact of gestational diabetes mellitus (GDM) on lipid metabolism in pregnant women and neonates at different gestational weeks, as well as the expression of placental lipid transport enzymes. Methods A retrospective analysis was conducted on clinical data from pregnant women and their neonates who delivered between January 2022 and December 2022. Placentas were collected from women who delivered between August 2023 and October 2023. Participants were divided into a GDM group and a control group based on the presence or absence of GDM. The serum lipids were compared between the two groups for both pregnant women and neonates. Additionally, differences in the expression of endothelial lipase (EL) and lipoprotein lipase (LPL) in placental tissue were compared between the two groups. Results A total of 541 full-term pregnant women were included, with 123 in the GDM group and 418 in the control group. There were 203 pregnant women with premature delivery, with 110 in the GDM group and 93 in the control group. Among full-term pregnant women, compared with the control group, the GDM pregnancies had greater weight gain and a higher rate of cesarean section, and the differences were statistically significant (P<0.05). However, the premature pregnant women with GDM had a smaller gestational age at delivery and less weight gain during pregnancy than those in the control group (P<0.05). Both in full-term and premature pregnancies, compared with the control group, triacylglycerol (TG) was higher and high-density lipoprotein cholesterol (HDL) was lower in the GDM group before delivery, and the difference was statistically significant (P<0.05). In GDM group, 77 full-term newborns were admitted to NICU, and 77 newborns were matched according to gestation week and birth date at a 1:1 ratio as control group; Total cholesterol (TC) and TG in the GDM group were higher than those in the control group, while HDL was lower than that in the control group, and the difference was statistically significant (P<0.05). In the placentas of full-term pregnant women, the expression of EL in the GDM group was significantly increased (P<0.05), but there was no difference in LPL expression between the two groups (P>0.05). In pregnant women with premature delivery, both EL and LPL had no differences in expression between the two groups (P>0.05). Conclusions GDM was associated with lipid metabolism disorders during pregnancy, but only in full-term newborns. Placental EL may be involved in the occurrence of lipid metabolism disorders in full-term newborns delivered by GDM mothers.