Prenatal ultrasound diagnosis of thrombocytopenia with absent radii

Thrombocytopenia with absent radii (TAR syndrome) is an autosomal recessive disorder in which congenital hypoproliferative thrombocytopenia and bilateral radial agenesis are constant features. After the birth of an affected infant, there is a 25% risk for recurrence in future pregnancies. Prenatal diagnosis is available for this disorder by means of fetal radiography, which can demonstrate the presence or absence of fetal radii at 16 to 20 wk gestation. We present a case of a pregnancy at risk for the TAR syndrome in which the affected fetus was detected by real-time ultrasound.