Introduction

Establishment and maintenance of pregnancy in a number of mammalian species depends upon a tightly regulated interaction between the semiallogeneic conceptus and the maternal uterine endometrium.The term "Maternal Recognition of Pregnancy" is attributed to Roger V. Short's paper titled "Implantation and the Maternal Recognition of Pregnancy" which was published in proceedings from the 1969 Symposium on Foetal Autonomy.Professor Short's landmark paper stimulated increased interest in elucidating how the conceptus signals its presence to assure maintenance of the corpus luteum beyond the normal length of the estrous or menstrual cycle to allow pregnancy to be established and maintained.Ten years following publication of Professor Short's paper, a Ciba Foundation Symposium entitled "Maternal Recognition of Pregnancy" brought together leading scientists to discuss the multiple mechanisms and pathways by which different viviparous species establish a successful pregnancy.The present volume on "Regulation of Implantation and Establishment of Pregnancy in Mammals" brings together current reviews from leading experts to address the diversity of mechanisms by which species establish and maintain pregnancy.Implantation in mice, dogs, pigs, cattle, sheep, horses, primates, humans and species in which embryonic diapause occurs are discussed.Reviews will provide current knowledge on the role of endometrial steroid receptors, adhesion factors, cytokines, interferons, steroids, prostaglandins, growth factors and immune cells involved with regulation of conceptus development.