Transient osteoporosis of the hip in pregnancy.

Transient osteoporosis of the hip is an uncommon bone marrow oedema syndrome of unknown pathophysiology affecting previously healthy pregnant women and young to middle-aged men. The disorder is characterised by hip pain, reduced mobility, and the risk of fracture, which is significantly higher in pregnant than in non-pregnant individuals. Diagnosis is by magnetic resonance imaging. Other than a single case-control study, published literature is limited to case series and case reports, with no evidence to guide management, risk of fracture, mode of delivery, safety of breastfeeding and risk of recurrence. An international pregnancy registry may be useful to try to answer some of these questions.