Abstract
Pregnancy- and lactation-associated osteoporosis (PLO) is a rare type of premenopausal osteoporosis, typically occurring during the third trimester of pregnancy and the early postpartum lactation period. This report presents a case involving severe multiple vertebral fractures due to PLO with low bone mineral density (BMD) and heightened bone turnover. A 39-year-old primiparous Japanese woman reported low back pain (LBP) starting at 28 weeks of pregnancy. The pain temporarily improved after delivery, although the LBP recurred and worsened 2 months into breastfeeding. Thereafter, the patient visited the Obstetrics and Orthopedic departments. Plain radiographs of the thoracic and lumbar spine showed loss of vertebral body height at the T4-12 and L1-3,5 vertebrae, leading to a diagnosis of 13 fractured vertebrae. BMD and serum bone turnover markers revealed low bone density and heightened bone turnover. In the absence of any identified alternative cause of secondary osteoporosis, the diagnosis was severe PLO with 13 vertebral fractures related to pregnancy and lactation. After treatment with bisphosphonates and an active vitamin D analog, the patient exhibited an increased BMD and normalization of bone turnover and resumed regular daily activities. Although the optimal PLO treatment strategy remains uncertain, bisphosphonates are an option; however, bisphosphonates can potentially affect the fetus through placental transfer. Therefore, careful consideration is required for patients planning pregnancy. Despite bisphosphonates' widespread use and cost-effectiveness, selecting PLO medications involves multiple factors, necessitating further research.