Death of one twin followed by extremely variable flow velocity waveforms in the surviving fetus.

Intrauterine death of one fetus after the second trimester in a twin pregnancy, with continuation of the pregnancy is a rare complication. The risks of morbidity and mortality for the surviving fetus are high. A 32-year-old woman was admitted to the antenatal ward at 27 weeks gestation because of intrauterine death of one twin. During the first 24 h after the death of one twin, Doppler ultrasound assessment showed a remarkable variability in flow velocity waveforms in the umbilical artery of the surviving fetus. Changes from reversed to normal end-diastolic flow velocities were recorded within 6 min. These findings are explained by twin-to-twin transfusion due to intravascular blood pressure changes, or by release of vasoactive substances by the dead fetus.