Motor deficits of lower limbs during pregnancy and the puerperium are relatively frequent. They are usually attributed to complications which are associated with neuroaxial techniques performed by the anesthesiologist. But there are other possible causes, such as transient osteoporosis of the hips. Transient osteoporosis of pregnancy is a rare and self-limited pathology of unknown etiology. The most severe complication that can occur are pathological fractures, mainly in the load joints. This pathology usually occurs in the third trimester of pregnancy and is showed up with pain and functional impotence of the lower limb affected. We present the case of a 35-year-old woman, 40+3 weeks of pregnancy who starts labour. Normally functioning epidural catheter is placed and finally cesarean section is decided because failure to progress; 48h later the patient begins with functional impotence and pain in the lower left limb. MRI is performed, epidural hematoma is ruled out and osteopenia of the hips is proved. The patient is diagnosed with transient osteoporosis of pregnancy.