Preterm labor, one of the common pathological phenomena during pregnancy, necessitates prompt and accurate detection to safeguard the health of both pregnant women and newborns. This study focused on placental alkaline phosphatase, a pregnancy-specific enzyme, and its potential role in identifying preterm labor. This study aimed to investigate the relationship between placental alkaline phosphatase, placental maturity, the nutritional status of newborns, and its utility in evaluating preterm labor. A total of 85 pregnant women with singleton pregnancy of more than 15 weeks of gestation admitted to our hospital from March 2022 to May 2023 were selected as study subjects. Our study revealed a positive correlation between PLAP levels and both gestational age and placental maturity (P < 0.05). Our findings indicated that with an increase in gestational age and placental maturity, there was a corresponding increase in placental alkaline phosphatase levels. However, there were no differences in placental alkaline phosphatase between pregnant women of Grade III and Grade II in terms of placental maturity (P > 0.05). There was a significant increase in placental alkaline phosphatase levels among pregnant women who gave birth prematurely (P < 0.05). The receiver operating characteristic curve showed that placental alkaline phosphatase had an excellent effect on the evaluation of preterm labor (P < 0.05). However, there were no significant differences in placental alkaline phosphatase between the pregnant women with and without postpartum complications (P > 0.05). Lastly, placental alkaline phosphatase was found to have an inverse relationship with levels of neonatal albumin and transferrin levels (P < 0.05).