To analyze the possible effects of the body mass index (BMI) and the blood lipid level of pregnant women during the first trimester of pregnancy on their premature delivery. Methods: From January 2022 to December 2022, the clinical data of 1186 singleton pregnant women who were registered in the obstetrics department of the hospital, and had regularly antenatal examined and hospitalized for delivery were selected as the research objects in this prospective cohort study. The general data, such as age, gravidity, parity and pre-pregnancy BMI, the levels of blood lipid during the first trimester of pregnancy, such as total cholesterol (TC), triglyceride (TG), high density lipoprotein (HDL-C), low density protein (LDL-C) and free fatty acid (FFA) of these women were collected. The neonates of these women were divided into group A (98 cases with preterm birth) and group B (1088 cases without preterm birth) according to whether the preterm birth occurred or not. Multivariate logistic regression was used to analyze the correlation between the pre-pregnancy BMI value and the blood lipid level of the women during the first trimester of pregnancy and their premature delivery. Results: A total of 1186 mother and infant pairs were included in this study,
among which, 98 (8.3%) newborns were preterm births. The age of the women in group A was significantly older than that of the women in group B. The gestational weeks of the women in group A at delivery were significantly shorter than that of the women in group B. The newborn weight in group A was significantly lower than that in group B (all P<0.05). There were no significant differences in the gravidity, the parity, the neonatal gender, the delivery mode and the neonatal Apgar score between the two groups (P>0.05). The proportion of the BMI <18.5kg/m2 (15.3%) of the women in group A was significantly lower than that (25.0%) of the women in group B, and the proportion of BMI≥24.0kg/m2 (20.4%) of the women in group A was significantly higher than that (7.8%) of the women in group B (all P<0.05), and there was no significant difference in the proportion of the women with 18.5kg/m2 ≤BMI< 24.0kg/m2 between the two groups (P>0.05). The levels of TC, TG, LDL-C and FFA of the women in group A were significantly higher than those of the women in group B (all P<0.05), and there was no significant difference in the HDL-C level of the women between the two groups (P>0.05). Logistic regression analysis showed that the pre-pregnancy BMI ≥24.0kg/m2, the high levels of TG, LDL-C and FFA of the women during the first trimester of pregnancy were the independent risk factors of their premature delivery (P>0.05). Conclusion: The pre-pregnancy BMI≥24.0kg/m2, and the elevated levels of TC, TG and FFA of the women during the first trimester of pregnancy are the risk factors of their premature delivery occurrence.