The present volume of the book series Advances in Anatomy, Embryology and Cell Biology brings together current reviews from leading experts to address the diversity of placentation by which species establish and maintain pregnancy. Development of viviparity and placentation in rodents, dogs, pigs, cattle, horses, marsupials, primates and elephants are discussed. 

The development of viviparity in mammals, including some invertebrate species, required the adaptation of the placenta to serve as a functional conduit for interplay between the semiallograftic fetus with the maternal uterus. Although the placenta protects the fetus from maternal immune rejection and provides oxygen and nutrient flow to support it to term across all the species, structural differentiation of this fetal-maternal interface can vary from simple to very complex. E.C. Amoroso contributed greatly to our early understanding and knowledge of placentation across a great variety ofspecies. His work on placentation provides numerous illustrations and histological sections which are used for teaching and stimulating research today. With this book, we want to pay tribute to his lifetime contributions to the field by reviewing our current understanding of the development of viviparity and placentation in different species.

The book is written for researchers, physicians and medical students working in the field of reproductive science or with an interest in placentation and viviparity.

Dr. Rodney Geisert is a Professor in the Division of Animal Sciences at the University of Missouri.  His research has focused on elucidating the expression of genes involved with regulation of early conceptus development and uterine function.  Research from his laboratory has described and identified the cellular and molecular processes involved with rapid trophoblastic elongation of pig conceptuses during early gestation. His laboratory has established that specific cellular changes in progesterone and estrogen receptors are involved with critical events in uterine secretion and embryonic development and placental attachment in the pig.  Rapid conceptus elongation and estrogen release are both essential for maintenance of pregnancy in the pig.  Although conceptus estrogen synthesis and release has been implicated in maternal recognition of pregnancy in the pig by others, his laboratory were the first to indicate that there were two phases of conceptus estrogen secretion needed for establishment of pregnancy to term.  The model established how placental attachment is initiated in the pig and regulation of conceptus cytokines such as IL-1b and prostaglandins such as PGE play an essential role in the initiation and maintenance of placental attachment. His laboratory has utilized gene editing technology to knockout key conceptus genes to determine their specific role in the establishment of pregnancy.

Dr. Tom Spencer is a Curators Distinguished Professor in the Division of Animal Sciences and Department of Obstetrics, Gynecology and Womens Health at the University of Missouri. His research program has discovered key physiological and genetic mechanisms regulating development and function of the uterus and placenta and seeks to translate that knowledge to improvement of fertility in domestic animals and humans. His research in reproductive and developmental biology utilizes a number of different animal models (sheep, beef cattle, dairy cattle, mice) as well as human tissues. Broadly, current discovery foci of the program include understanding: (1) cellular and molecular mechanisms regulating gland development and function in the uterus using genetically engineered mice and sheep; (2) genetic pathways regulating fertility in beef cattle, dairy cattle, mice and humans; and (3) physiological pathways regulating pregnancy recognition and establishment using cattle, sheep and mice. Notable research efforts established the essential roles of uterine glands in implantation and pregnancy establishment and elucidated how endogenous retroviruses regulate placental development in mammals.

Mammalian Placentation: A Tribute to E.C. Amorosos Contributions to Placenta Development.- The Evolution of Viviparity in Vertebrates.- Development of Pre-Implantation Mammalian Blastocyst.- Placentation in Marsupials.- The Early Stages of Implantation and Placentation in the Pig.- Placentation in Equids.- Implantation and Placentation in Ruminants.- Canine Endotheliochorial Placenta - Morpho-Functional Aspects.- Placentation in The African Elephant (Loxodonta Africana).- Development of the Mouse Placenta.- Placentation in the Human hnd Higher Primates.