Inclusion Criteria:  Age ≥18 years old; Nulliparae with single term cephalic pregnancy; Preparing to give vaginal delivery under epidural analgesia.  Exclusion Criteria:  Basal body temperature ≥37.3℃; Presence of serious pregnancy complications (such as severe preeclampsia, placenta accreta, HELLP [Hemolysis, Elevated Liver enzymes, Low Platelet count] syndrome, placenta previa, abruption of placenta, or hyperthyroidism); History of hyperthyrodism, including hyperthyrodism in pregnancy; Taking sedatives and/or analgesics within one week before planned delivery; American Society of Anesthesiologists classification >class III; Contraindications to epidural puncture, including central nervous system diseases (such as poliomyelitis), spinal diseases (such as intraspinal mass, lumbar disc herniation, history of spinal trauma, etc.), abnormal blood coagulation, etc.; Presence of infections, including obstetric infections, systemic infections (such as sepsis, bacteremia), or infections at the puncture site or adjacent sites; Other conditions that are considered unsuitable for study participation; Refused to participate in the study.