Prevalence:

• Spontaneous death of one fetus occurs in 1% of monochorionic twins. 

Implications:

• Death of one twin is associated with acute hemorrhage from the co-twin into the fetoplacental unit of the dead one. In the co-twin there is a 15% risk of death and ≥ 25% of the survivors have severe neurological injury. There is also a high risk (60-70%) of preterm birth.
• If death of a fetus occurs at <24 weeks' gestation the co-twin is more likely to also die but if it survives, neurologic damage may be less; if death occurs >24 weeks the co-twin is more likely to survive but also more likely to suffer brain damage.

Management:

• Ultrasound examination to estimate whether the death of the fetus occurred within the previous 48 hours or earlier (mild generalized edema, ascites and pleural effusions), and assessment of the survivor for evidence of brain hemorrhage, heart failure and hyperdynamic circulation with high middle cerebral artery peak systolic velocity (MCA PSV).
• Death at <48 hours and MCA PSV ≥1.5 multiple of the median: intrauterine blood transfusion and repeat Doppler 5-10 hours later. If the PSV is again >1.5 multiple of the median another transfusion is necessary. If there is polyhydramnios and the cervical length is <20 mm consider amniodrainage.
• Death at <48 hours and MCA PSV <1.5 multiple of the median: repeat Doppler studies within 24 hours. If the PSV becomes >1.5 multiple of the median an intrauterine blood transfusion is necessary. If there is polyhydramnios and the cervical length is <20 mm consider amniodrainage.
• Death at >48 hours and no evidence of fetal heart failure: expectant management irrespective of MCA PSV. If there is polyhydramnios and the cervical length is <20 mm consider amniodrainage.
• If the fetus survives: neurosonography should be carried out in 2 and 4 weeks and MRI at 32 weeks to determine if there is evidence of brain damage. If brain development, fetal growth and Dopplers are normal there is no need for early delivery. If there is evidence of brain damage, in some countries pregnancy termination would be a legal option.