Background We aimed to evaluate the association of metabolic syndrome (MetS), its components and lipid profile in mid-pregnancy with preterm delivery and preterm premature rupture of membranes (PPROM). Methods This prospective cohort study was conducted on 203 pregnant women between 24-28 weeks of gestation, undergoing the gestational diabetes screening test with 50 gr glucose challenge test (GCT). Fasting serum total cholesterol, low-density lipoprotein cholesterol (LDL-C), high -density lipoprotein cholesterol (HDL-C), and triglyceride (TG) levels were measured during the week after GCT assessment. Information on the participants' pre-pregnancy weight, demographic/ reproductive characteristics, and height and blood pressure (BP) measurements were documented at baseline entry into the study. Metabolic syndrome was defined as the co-existence of 3 or more of the following criteria: Body mass index (BMI) before pregnancy≥30 kg/m2, BP≥130/85 mmHg, GCT≥140mg/dl, TG≥150mg/dl, and HDL-C≤50mg/dl. All participants were followed through routine prenatal care, up to delivery. Any deliveries or rupture of membranes of less than or equal to weeks of pregnancy, were considered preterm delivery and PPROM respectively. Statistical analysis was performed by SPSS V.20, and p-value of less than 0.05 was considered significant. Results MetS was detected in 10 (4.9%) of participants. Logistic regression analysis showed HDL-C levels, and hypertension had significant effects on spontaneous preterm delivery occurrence [(OR: 0.952, 95%CI: 0.910_0.995), (OR: 1.629, 95% CI: 1.554_1.709) respectively], but no statistically significant results were found for PPROM. Conclusions Low HDL-C levels and hypertension in mid-pregnancy may increase the occurrence of spontaneous preterm deliveries, indicating that MetS and its components should be monitored more closely in pregnancy.