A crucial factor in human reproduction is the length of gestation. The proper timing of birth ensures that the young individual is sufficiently developed to survive and adapt in the extrauterine environment and that the mother is able to provide nutrition and protection to the newborn. This volume reviews research in the area of the maintenance and termination of the pregnancy. The main aim of this research is to reduce the incidence of premature birth which is the primary cause of preterm death worldwide. Contributors to this volume are active researchers into perinatology and they provide chapters which represent a wide spectrum of perinatal research covering both human and non-human primates. The interaction between the mother, the foetus and the placenta is highlighted, with examinations of trophoblast function, myometrial contractility, and the endocrine-paracrine systems fully discussed.