THE SEQUENTIAL IN-UTERO DEATH OF HETEROKARYOTIC MONOZYGOTIC TWINS - ACASE-REPORT AND LITERATURE-REVIEW

A case of monozygotic twins in a 19-year-old primigravida is presented . Ultrasound examination at 15 weeks' gestation showed one twin to hav e a cystic hygroma and hydrops fetalis. The other twin appeared normal . The twins appeared to occupy the same amniotic cavity. Fluid was tak en from the cystic hygroma under ultrasound guidance for karyotyping a nd this showed 45,XO chromosomes. Conservative management was adopted. Serial ultrasound examination showed deteriorating hydrops and at 26 weeks the first twin died. Intensive monitoring of the remaining twin was undertaken with weekly ultrasound, cardiotocography (CTG), and clo tting screens. At 29 weeks' gestation the CTG and clotting were normal , but ultrasound revealed that multicystic encephalomalacia had develo ped in the Second twin. A very thin dividing membrane was seen for the first time between the twins. The parents decided to terminate the pr egnancy. Prior to an intracardiac potassium chloride injection, a feta l blood sample was taken which revealed 46,XX chromosomes and a normal clotting screen including natural anticoagulant levels. Labour was th en induced. Delivery took place 5 h later and the woman made an uneven tful recovery. The mechanism for genetic differences between monozygot ic twins is discussed and the literature reviewed. A non-disjunction e vent around the time of splitting of the twins is proposed as the caus e. The prognosis for the remaining twin is also discussed, as is the p athogenesis of the cerebral damage.