Osteonecrosis is thought to result from the temporary or permanent loss of blood supply to the bones. Without proper nutrition, the bone tissue dies, is resorbed, and collapses. If the process involves the bones in a joint, it often leads to collapse of the joint surface. Four new cases of bilateral osteonecrosis of the femoral head occurring during pregnancy are described, with pathologic examination of core tissue biopsy substantiating the diagnoses. Operative and nonoperative management included anti-inflammatory medication, pulsating electromagnetic fields, core decompression, and total hip replacement. A review of the literature is undertaken to document the reported cases of osteonecrosis of the femoral head associated with pregnancy. Idiopathic osteoporosis of the femoral head is a condition that mimics osteonecrosis of the femoral head and can be a challenge in diagnosis during the latter stages of pregnancy. Bilateral osteonecrosis of the femoral head during pregnancy is rare. Patients may have other predisposing factors leading to femoral head necrosis. Transient osteoporosis of the femoral head during pregnancy can present with a clinical picture similar to osteonecrosis. Avascular necrosis of the femoral head should be considered in the differential diagnosis of pain about the hip developing during pregnancy or in the immediate postpartum period.