Lethal osteogenesis imperfecta: Second trimester sonographic diagnosis in a twin gestation

A second trimester sonographic diagnosis of twins discordant for lethal osteogenesis imperfecta is reported. A 29 year old primigravida was referred for an ultrasonogram at 20 weeks and 2 days' gestation after a 24 cm fundal height was noted. Examination revealed an intrauterine dichorionic twin pregnancy. The male fetus was appropriately grown with sonographically normal anatomy. The hypoechoic and compressible calvarium of the female co-twin permitted unusually clear visualization of the intracranial anatomy. This fetus exhibited multiply fractured femora, one of which measured 1.6 a cm in length, tetramicromelia, and a hypoechoic skeleton. Accurate and timely diagnosis of the type II osteogenesis imperfecta allowed the parents to be counseled appropriately and the pregnancy managed in accordance with the well-being of the viable co-twin.