PreImplantation Factor and Endocrinology of Implantation and Establishment of Early Pregnancy: A Contemporary View

The earliest stages of pregnancy are marked by countless changes in the maternal environment. A specific coordination of activity is required for a successful pregnancy, starting early in the menstrual cycle. Early establishment of maternal-fetal crosstalk is critical for the progression of pregnancy. Many factors, both maternal and fetal derived, play specific and important roles immediately following fertilization, through implantation and beyond. Here we present a review of some of the key factors involved with a focus on PreImplantation Factor (PIF), a small peptide secreted only by competent embryos, which carries an important role required for pregnancy progression.