PHYSICAL EXAMINATION

LABORATORY STUDIES

DIAGNOSIS

Placental abruption

PATHOPHYSIOLOGY OF KEY SYMPTOMS

The third trimester is a time of rapid fetal growth and maturation. The maternal fetal interface is created by the fetal placenta and the maternal uterus to facilitate the delivery of nutrients and removal of wastes from the fetus. The close approximation of fetal placental capillaries and the maternal uterine capillaries provides a very large surface area to facilitate diffusional will exchange (Fig. 82-1). In addition, fetal characteristics enhance the movement of oxygen and glucose. Fetal hemoglobin has a higher affinity for oxygen then does maternal hemoglobin, enhancing the delivery of oxygen to the fetus. Fetal hematocrit is higher than maternal hematocrit, enhancing the oxygen-carrying capacity of the fetal blood. Glucose delivery to the fetus is enhanced by the high maternal plasma glucose levels. Throughout gestation, the growing fetus places additional demands on nutrient and waste exchange at the placenta.

FIGURE 82–1 Top, Organization of the mature placenta. Bottom, Relation of the fetal blood in the villus capillaries to the mother’s blood in the intervillous spaces.

(Modified from Gray H, Goss CM: Anatomy of the Human Body, 25th ed. Philadelphia, Lea & Febiger, 1948; and from Arey LB: Developmental Anatomy: A Textbook and Laboratory Manual of Embryology, 7th ed. Philadelphia, Saunders, 1974.)