The vaginal microbiome plays a crucial role in women's health, primarily composed of beneficial bacteria such as Lactobacillus, which help maintain an acidic environment in the vagina, preventing the growth of pathogens. Research indicates that the vaginal environment during pregnancy is more conducive to the growth of Lactobacillus. Traditionally, perineal disinfection is performed during vaginal delivery; however, studies have shown that excessive use of disinfectants like povidone-iodine may reduce the presence of Lactobacillus in the vagina. Furthermore, not using perineal disinfection does not increase the risk of postpartum infections for mothers and infants, and may even benefit the development of the newborn's microbiome. Considering the medical costs and nursing labor involved, this study aims to compare the effects of different perineal preparation methods on postpartum infection rates and medical costs, with the goal of improving maternal and infant care quality during delivery and reducing healthcare costs.

5、 Method This study employs an experimental research design. After obtaining informed consent from participants, they will be randomly assigned to either the control group or the experimental group using a random number table. The control group will undergo perineal preparation using clean water, while the experimental group will use povidone-iodine for disinfection. The study will document patient demographics, prenatal vital signs, maternal and infant postpartum temperatures, blood test results, and oral bacterial culture outcomes to monitor postpartum infection rates. The REEDA scale will be used to assess perineal wound healing.

6、Expected results： The anticipated results indicate that using clean water for perineal preparation will not increase the risk of postpartum infections for mothers and infants, while also saving medical costs. Additionally, water disinfection may allow newborns to acquire beneficial bacteria such as Lactobacillus from the mother's vagina during delivery, promoting healthy gut microbiome development.

Inclusion Criteria:

Maternity:

• Born after 37 weeks of pregnancy;
• Pregnant women with low-risk pregnancy;
• Be able to communicate in Mandarin and Taiwanese, and be able to read Chinese;
• A single fetus with a cephalic position;
• Aged 18 years or above (inclusive) with clear consciousness and no cognitive impairment;
• Do not use antibiotics during pregnancy;
• There are no fetal diagnostic abnormalities during pregnancy check-up.

Newborn:

• Newborns over 37 weeks
• Apgar Score is greater than 7 points in the first minute of life
• Having given birth to a newborn and undergoing perineal cleaning/disinfection methods specified in the study during the second stage of labor

Exclusion Criteria:

• The mother's water broke for more than 18 hours during labor;
• Mother had a fever;
• Used vacuum suction during delivery;
• Shoulder dystocia;
• Fetal distress;
• A perineal wound of 3 degrees or above