INTRODUCTION: We present a case report on the clinical management of a pregnant patient with type I osteogenesis imperfecta (OI). OI is an inherited disease with an incidence in pregnancy of 1 in 25 000 to 30 000. The basic pathology is a defective maturation of type I collagen. CASE PRESENTATION: A 35-year-old primigravida with OI and a prior history of 30 fractures is presented. During pregnancy, all antenatal ultrasound scans showed normal fetal development. At 21 weeks of gestation, the patient had to be immobilised for 3 weeks due to premature labour. At 32 weeks of gestation, the patient developed increasing pain of the lumbar spine and arthralgia of the hip joints leading to hospitalisation. After a new fracture could be excluded, treatment with metamizole and a daily dose of 1000 mg of calcium and 800 IU of vitamin D was initiated. Since her first visit at 13 weeks of gestation, the patient was monitored by Quantitative Ultrasonometry (QUS) of the phalanges to estimate the fracture risk. There was a clinically relevant continuous decrease in the amplitude-dependent speed of sound (AD-SOS) and the T-score from 2052 m/sec and - 1.03 at 12 weeks 6 days of gestation to 2004 m/sec and - 1.71 at 32 weeks 5 days of gestation which correlated with the increase in pain. At 33 weeks 5 days of gestation, an elective caesarean section was performed due to intolerable pain and increased fracture risk. CONCLUSION: During pregnancy, our patient with OI showed a continuous decline in QUS variables and T-scores as well as a clinically significant increase in lumbar pain and arthralgia of the hip joints finally leading to an elective caesarean section. During pregnancy, no maternal fracture occurred, and the neonate showed a normal skeletal status without clinical signs of OI.