**1. Introduction**

Multiple pregnancies are the result of one of the three possibilities: a fertilization of two or more oocytes from different spermatozoids, a single fertilization followed by a splitting of the zygote, or a combination of both [1]. These pregnancies have an increased risk of several complications for both mother and fetuses, such as diabetes mellitus, hypertensive disorders associated with pregnancy, preeclampsia, anemia, hyperemesis, hemorrhage, and cesarean

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

delivery [2–5] in the maternal side and higher risk of fetal anomalies, fetal demise, neonatal death [6], and preterm birth in the fetal side [7].

The term "third circulation" that represents an "area of transfusion" and the potential harmful effect of vascular connections between the fetuses was first described by Schatz in 1896 [20]. In 1965, Naeye [21] identified the effect of chronic nutritional deprivation on the size of organs in one twin while appreciating that transfusion to the other increased the hemoglobin concentration and hematocrit, with subsequent cardiomyopathy and hypertension. Since then, several authors have proposed diagnosis criteria and different kinds of treatments of the MC pregnancy problems. In this session, the main complications of the MC gestations will be discussed.

Complications in Monochorionic Pregnancies http://dx.doi.org/10.5772/intechopen.83390 127

One of the first suggestions of this disease in history lies in a Dutch painting from 1617 named the Early-Deceased Children of Jacob de Graeff and Aeltge Boelens that illustrates two children. One of them is pale and the other plethoric (**Figure 1**). Twin to twin transfusion syndrome is one of the main complications that occurs in about 10–15% of the MC pregnancies

If left untreated, TTTS mortality rates are about 70–100%. Perinatal mortality is the result of either miscarriage or very preterm delivery as a consequence of severe polyhydramnios and

**Figure 1.** The Dutch painting the Early-Deceased Children of Jacob de Graeff and Aeltge Boelens shows two male twins:

uterine distention or fetal demise due to severe cardiovascular disturbances [24, 25].

**3.1. Twin to twin transfusion syndrome**

one pale and the other plethoric.

with an overall incidence of 3 in 10,000 pregnancies [22, 23].

It is known that monochorionic (MC) pregnancies have higher rates of fetal morbidity and mortality when compared to dichorionic (DC) ones [1, 8, 9]. Besides that, the MC pregnancies have specific complications such as the twin to twin transfusion syndrome (TTTS), the selective fetal growth restriction (sFGR), the twin anemia polycythemia sequence (TAPS), and the twin reversed arterial perfusion sequence (TRAPS). Most of these complications can be managed and treated in order to decrease the fetal morbimortality.
