Adaptations to Pregnancy and Related Nursing Care

Adaptations to pregnancy include physiologic and psychosocial changes that occur in a pregnant patient in response to a developing fetus.

Physiologic changes during pregnancy affect the body from head-to-toe, including the cardiovascular, respiratory, and reproductive systems.

Starting with the cardiovascular system, pregnancy is considered a high-volume state, meaning that blood volume gradually increases during the pregnancy to provide circulation to expanding maternal tissues; exchange nutrients, oxygen, and waste in the placenta; and create a reserve for blood loss during delivery.

The composition of blood changes too. Both plasma and red blood cells increase; although there’s a larger increase in plasma, which leads to dilutional anemia, sometimes referred to as a physiologic anemia of pregnancy, where hemoglobin and hematocrit levels are decreased.

White blood cells, primarily neutrophils, increase along with clotting factors, like VII, VIII, X, and fibrinogen. Increased clotting factors minimize bleeding after delivery but also increase the risk of venous thromboembolism.

Now, in order to pump the extra blood and increase cardiac output, the heart rate increases by 10 to 15 beats per minute; the stroke volume, or the amount of blood pumped with each heartbeat, increases as well; and the heart enlarges from this extra workload.

In fact, the uterus also enlarges and pushes on the diaphragm, causing the heart to be slightly displaced up and to the left. Blood pressure decreases despite increased blood volume, due to elevated progesterone and estrogen, which cause vasodilation and decreased vascular resistance, increasing the risk of orthostatic hypotension.

Moreover, when lying flat, the weight of the uterus can compress the inferior vena cava, reducing blood return to the heart. As a result, cardiac output decreases and supine hypotension occurs, causing dizziness and lightheadedness.

Also, as less blood circulates to the placenta, fetal hypoxia can occur. This can be avoided if patients turn to their side or place a pillow under their lower back when lying down, to relieve pressure from the inferior vena cava and restore venous return to the heart.

Next, there are changes in the respiratory system to accommodate an increase in oxygen consumption. Tidal volume, or the amount of air inhaled and exhaled with each breath, rises along with respiratory minute volume, or the amount of air breathed every minute, increasing the amount of oxygen and carbon dioxide exchange.

As the expanding uterus places pressure on the diaphragm, the lungs have less room to expand, which can cause shortness of breath until the fetus descends into the pelvis later in the third trimester. Additionally, elevated progesterone levels increase the sensitivity of the respiratory center in the medulla oblongata and decrease airway resistance.