Data collection
UTERUS
We collected women’s baseline MHL via an online questionnaire on the day when women were admitted to the hospital. Women were asked to access the online questionnaire via their own electronic devices (smartphones, pads or laptops) and independently complete all questions. Responses with missing answers to the PMHLS questions or submitted in less than 2 minutes or over 30 minutes were considered invalid and excluded. Women with a PMHLS score of 27 or less were asked about their willingness to be included in the study. The women’s social ID number and social-demographic information, including age, ethnic group (Han people/minority), marital status (married/other), education background (primary and below/junior school/high school/college/undergraduate and above), residential area (rural area/county/urban), occupational status (unemployed/employed), monthly family income, insurance type (self-paying/new rural cooperative medical system/worker with medical insurance/other), body mass index (BMI) before pregnancy, parity (unipara/multipara), history of scarred uterus (no/yes), any pregnancy and childbirth-related educational sessions before participating in the current study (no/yes), and number of terminations, were collected from the women via the baseline questionnaire. Information about birth modes (spontaneous labour/caesarean section), postpartum maternal-infant health outcomes and health behaviours was obtained from the hospital’s patient electronic medical record system. When women visited the hospital for a regular 42-day postpartum check-up, their MHL at 42 days postpartum was collected via the same questionnaire used at baseline. Two research nurses checked the quality of the responses. Again, responses with missing answers to the PMHLS questions and those completed in less than 2 minutes or over 30 minutes were considered invalid and excluded.