Pregnancy- and lactation-associated osteoporosis is a rare disease. Although researchers have reported a few cases, there are no established diagnostic criteria for pregnancy- and lactation-associated osteoporosis. However, a diagnosis can be easily obtained by an accurate medical interview, physical examination, imaging studies, and laboratory data, including bone mineral density measurement. This disease should be suspected when a woman presents with severe back pain in the late stages of pregnancy or the early postpartum period. An accurate and prompt diagnosis helps with appropriate treatment and prevents the progression of the disease.