[Primary observation of a congenital intracranial teratoma in a twin with a healthy brother].

Primary intracranial teratomas are rare germ cell tumors arising from embryonic tissues, which contain cellular or tissue derivates from all three germ layers. Today the early intrauterine diagnosis by ultrasound is possible. We first describe a patient with such a tumor which was diagnosed by routine ultrasound in the 33rd week of gestational age in a twin-pregnancy, of which the 2nd twin developed normally. This must be considered in the obstetrical situation. In such a case the parents should be advised accordingly.