**14. Conclusion**

In monochorionic placentas the risk of vascular anastomoses could result in disruption that compromises the fetus. These hemodynamic abnormalities are more prevalent after the death of one co-twin; however, it can happen even in surviving infants. This process of hypoxia and ischemia could affect several organs such as the brain (microcephaly, hydrocephalus or hydranencephaly), the gastrointestinal system (intestinal atresia), the kidney, and the skin

Malformations in twins affect the abdominal wall, skull, and chest, as well as the cardiac, musculoskeletal, urogenital and central nervous systems. They are related to embryonic midline fates (neural tube and cardiac defects), hemodynamic instability of the placenta (brain lesions, limb reduction, cardiac defects, renal agenesis, aplasia cutis and intestinal atresia), and anomalies associated with prematurity (patent ductus arteriosus and retinopathy) [113].

The management of discordant anomalies in monochorionic twins is a great challenge when parents decide to keep the pregnancy. The normal fetus is at increased risk of prematurity and its consequences. The major problem occurs after the death of the discordant fetus for con‐ genital anomalies, which increases the risk of death of the normal co-twin around 10-25%. The risk of brain lesions in the surviving infant is approximately 25% [114]. Also, the rate of perinatal death in twins associated with congenital malformations is approximately 15% [115, 116]. Therefore, it is very important to maintain a strict surveillance during the prenatal in

In general, it is known that multiple pregnancies increase the risk for fetal death. Whenever there is death of one fetus, there is also increased rates of prematurity, neurological sequel and death of the other twin. Chorionicity is determinant in these cases, with more unfavorable

The vanishing twin syndrome occurs after the sonographic diagnosis of a twin pregnancy, in which a subsequent ultrasound study fails to identify both fetuses. The dead embryo may be completely reabsorbed or even become incorporate into placental membranes, resulting in

Later single twin demise in monochorionic twins could also happen due to multiple reasons such as infection, chromosomal or structural anomaly, placental factors or even maternal problems (hypertensive disorder, thrombophilia) [118]. In this scenario, the chance of death of the other fetus and the risk of neurological sequel is around 25% [119]. This can be explained by hemodynamic fluctuations and ischemia, where the blood volume of the living fetus is diverted to the vascular space of the dead fetus, thereby causing multicystic encephalomalacia. Serial ultrasonographic monitoring for brain damage is mandatory and it can be complement‐ ed by magnetic resonance imaging. Although the results were inconsistent, some physicians have reported fetal blood sampling and intrauterine transfusion in the surviving twin [118, 120]. Others highlighted the use of ultrasonographic evaluation of the peak systolic velocity

in the middle cerebral artery for detection of fetal anemia [121].

(aplasia cutis) [112].

222 Contemporary Gynecologic Practice

**12. Fetal death**

order to diminish the risks for the normal co-twin.

prognosis in monochorionic pairs [117].

fetus papyraceous [23, 118].

The frequency of multiple pregnancies has been increasing in the last decades. Currently, it seems to have stabilized mainly due to a more strict regulation of assisted reproductive techniques. Advances in medicine allowed for earlier diagnosis not only of twin pregnancy but also chorionicity and amnionicity characteristics, which are directly implied in adverse outcomes and prognosis. Despite the various abnormalities related to monochorionic preg‐ nancies, efforts have been made to overcome medical and parenting challenges. Even though twin pregnancies have many peculiarities and must be followed regularly by well-trained professionals, there is no evidence that planned cesarean delivery may diminish fetal mor‐ bidity and death.
