Fig. 2

Study design. The combination of disease codes of closed osteoporotic fractures and medical procedures for fractures 0–23 months after delivery were defined as “occurring of osteoporotic fractures.” The disease code and the health check-up data recorded 12–36 months before delivery were used as confounders, whereas the body mass index recorded 12–36 months before delivery was used as the exposure in this study. The data recorded at the latest health check before delivery were used. However, the data during pregnancy were not used. If the latest data differed depending on the item in the medical check-up data, we used the data from the medical check-up when the body mass index was recorded at the nearest time before delivery