Sampling
After registering the study on the website of the Iranian Registry of Clinical Trials (IRCT) (IRCT20170506033834N7) and receiving a referral letter, the researcher (first author) introduce herself to the hospital officials and attended the delivery ward. After birth, she introduced herself to primiparous women with mediolateral episiotomy with an incision length of 5 cm or less, and after evaluating other inclusion criteria, explained the objectives and method of the study to postpartum women. The eligible women willing to participate in the study completed the written informed consent form. The researcher filled out the demographic and obstetric characteristics based on their medical records. Participants were assigned into the probiotic and placebo groups in a ratio of 1: 1 by block randomization using Random Allocation Software (RAS) with a block size of 4 and 6. Envelopes were prepared according to the number of samples and capsules were placed inside the envelopes. Each envelope was numbered from 1 to 74. The envelopes were opened in the order in which the participants entered the study and the type of intervention was determined. Their preparation was performed based on the allocation sequence by a non-involved person in the sampling. In the present study, the researcher, participants, and outcome assessor were blinded.