Physiology

Abstract

The second trimester of pregnancy has been studied far less intensively than have the trimesters preceding and following it. That the first and third trimesters have received academic emphasis is not surprising. Physiologically speaking, the concerns of early pregnancy center on fertilization, ovum transport, the mechanics of implantation, and the need to provide a nutrient supply for the embryo as well as a place for further growth and development. From the pathophysiologic point of view, there is a fear of early pregnancy loss which focuses heavily upon the relatively large risk of spontaneous abortion and the risks of teratogenic influences. By the third trimester, concern centers on the final spurt of fetal growth, the weeks of prelabor, and the process of labor itself. All of these considerations have been studied extensively in the past two decades. Particular attention has been focused on problems of premature labor, intrapartum death, unanticipated hemorrhagic processes, and dysfunctional labor.