Osteogenesis imperfecta (OI) is a heterogeneous group of genetic bone disorders that are characterised by decreased bone mass, increased bone fragility and susceptibility to fractures. The severe, perinatal lethal form (Type II) (OMIM 166210) is characterised by bone fragility, with perinatal fractures, severe bowing of long bones, undermineralisation, and death in the perinatal period owing to respiratory insufficiency. The overall prevalence of OI Type II is unknown. There are three subtypes of OI Type II (A, B and C) that are characterised by different radiological features, and may be caused by different genetic faults. Two fetuses with OI Type IIA are presented.