Magnetic resonance imaging and ultrasonography in the antenatal evaluation of conjoined twins.

Magnetic resonance imaging and sonography were used as diagnostic aids in the antepartum evaluation of two sets of conjoined twins. Magnetic resonance imaging was performed at 20 weeks' estimated gestational age on thoracopagus/omphalopagus twins and on omphalopagus twins at 20 and 30 weeks. Magnetic resonance imaging is a complementary adjunct to ultrasonography and provides additional anatomically precise clinical data. The advantages of this noninvasive technique include a large diagnostic window allowing total fetal imaging with excellent resolution of tissue composition. Unlike computerized tomographic imaging, there is no associated radiation exposure. The principal disadvantages of magnetic resonance imaging at this time are the cost of the equipment and the lack of real-time imaging capability.