**1. Introduction**

The placenta is a fascinating organ, unique in that it is critical for human development, yet becomes dispensable once extra-uterine life has begun. During embryogenesis, the placenta functions as the maternal-fetal interface and performs the roles of the lungs, liver, and kidneys for the growing gestation, as well as providing nutrition. Placental development is intriguing in the balancing act performed when invading the maternal endometrium to permit growth of the blastocyst, however, unlike neoplasms, its invasion and growth has set end points, beyond which pathologic states can develop **Pictures 1**–**6**.

The term *placentation* is defined as the formation or arrangement of the placenta in the body of a woman or female animal. As discussed later in this chapter under the ectopic implantation discussion, the definition of placentation will be extended beyond implantation only in the uterus to "the body".

**Picture 1.**  *Placenta previa with placenta accreta.* 

**Picture 2.**  *Increased endometrial invasion by placental vasculature suspicious for placenta accreta.* 

Over the last couple centuries, scientific investigation has allowed us to understand the embryology, anatomy, and physiology of normal and abnormal placentation on both an organ system and a molecular level. We have established and continue expanding our understanding of how placental abnormalities and malfunctions contribute to the development of maternal, fetal, and neonatal disease, with

### *Placental Abnormalities DOI: http://dx.doi.org/10.5772/intechopen.81579*

current investigations examining the correlations between in utero conditions on future disease development during childhood and adulthood. Placental organogenesis, development, function, and malfunction remain fields of vast potential research

**Picture 3.**  *Placental separation.* 

**Picture 4.**  *Velamentous cord insertion.* 

### **Picture 5.**

*Placenta previa with placenta percreta invading the bladder.* 

### **Picture 6.**  *Placenta previa with measured Cervical Canal.*

that are covered in depth in other chapters in this book. The goal of this chapter is to delineate the real-world implications of placental abnormalities and provide the reader with a basis for understanding the other chapters that delve into microbiology, genomics, immunohistochemistry, and biochemistry of the placenta **Table 1**.

**Table 1.** 

*Placenta previa and placenta accreta by number of cesarean deliveries.* 
