Fertilization and normal embryonic and early fetal development

The anatomy and physiology of placental and embryonic development is a field where medicine exerts its greatest impact on early pregnancy at present time, and it opens fascinating aspects of embryonic differentiation. Clinical assessment of those stages of growth relies heavily on three-dimensional (3D) and four-dimensional (4D) sonography, one of the most promising forms of noninvasive diagnostics today. The embryologic phenomenon, once matters for textbooks, is now routinely recorded with outstanding clarity. Fertilization is the end of the complicated process of conjunction of gametes by entering one spermatozoon into the oocyte. Receptors of those factors have been identified on human conceptus. Synthesis of many of those factors has been detected in early conceptus itself or in maternal tissues; therefore, it is reasonable to conclude that these factors act as autocrine or paracrine agents that promote the early development.