Ultrasound in Multiple Pregnancy Complicated with Single Intrauterine Fetal Demise

Fetal death in utero is more common in multiple pregnancy, compared to singleton pregnancy. Moreover, the death of one of the fetuses in utero raises issues related to etiology, maternal-fetal and fetofetal interrelationship. Just like in many other circumstances of multiple pregnancy, chorionicity has a decisive role. Due to vascular anastomoses and inter-fetal circulation specific to monochorionic placentation, the death of one of the fetuses in utero, by subsequent inter-fetal hemodynamic fluctuations is responsible for approximately 20-40% of the anomalies that occur on the surviving fetus. Singleton fetal death is a risk of 20% for polycystic encphalomalacia and premature birth of the survivors in monochorionic pregnancy. Cerebral anomalies of the surviving fetus result from several mechanisms, the most important one being the hypoxic-ischemic one, eventually resulting in intraventricular haemorrhages and periventricular leukomalacia. The hypovolemic shock the surviving fetus feels is also an important mechanism. According to this theory, the deceased fetus acts on the survivor through a "faucet" effect, which basically bleeds to the deceased fetus, lacking vascular resistance. This rapid transfusion syndrome is done through superficial arterio-arterial and veno-venous anastomoses. The management of the death of one of the fetuses in utero in multiple pregnancy is clearly differentiated by the chorionicity related problem. If in the dichorionic multiple pregnancy the attitude is basically clearer and is particularly based on the expectantly conservative management and systematic fetal evaluation, clearly being subject to the risk of miscarriage or premature death, in monochorionic pregnancy, this attitude is much more complex. If the fatal event of one of the fetuses occurs in the second trimester of pregnancy, the ultrasound surveillance of the surviving fetus is essential, the decision of elective intervention is sensitive, and the prognosis is inevitably subject to hazard.