A pregnant woman at 28 weeks gestation is lying supine during a non-stress test when she suddenly becomes pale, diaphoretic, and reports feeling dizzy and nauseous. Her blood pressure drops from 110/70 mmHg to 85/45 mmHg. What is the most appropriate immediate nursing intervention?

Supine hypotension syndrome results from vena cava compression by the gravid uterus. Immediate left lateral positioning is the most effective intervention to relieve compression and restore normal circulation, preventing maternal and fetal complications.

Clinical Judgment This question assesses the ability to recognize an acute change in condition in a third-trimester pregnant woman and determine the Priority Intervention. The key is to identify that the cause of the symptoms is Supine Hypotension Syndrome. When the mother lies in a supine position, the enlarged uterus compresses the Inferior Vena Cava, preventing venous blood from returning to the heart. This leads to a sudden drop in cardiac output, a fall in blood pressure (120/80 → 90/50), and symptoms of inadequate cerebral perfusion (dizziness, pallor, diaphoresis) and nausea. The quickest and most effective solution is to remove the cause of the compression, that is, to move the uterus away from the inferior vena cava. Therefore, the correct answer is to immediately turn her onto her left side. Memory Tip: Supine = Side (Left Lateral)! Or remember "Left Lateral for Low pressure." If symptoms appear in the supine position, turning her onto her side is the very first thing to do. KR vs US In Korea, it is well known as 'Vena Cava Compression Syndrome' or 'Supine Hypotension Syndrome,' and inducing a left lateral position is standard practice in delivery rooms and during prenatal examinations. The NGN places even greater emphasis on Clinical Judgment and the selection of an immediate intervention based on these physiological changes.

Clinical Practice Guide
Avoid placing all mothers after 20 weeks of pregnancy in a supine position. If an examination or procedure is necessary, be sure to support their back with a pillow or towel to maintain a left lateral tilt. When symptoms occur, 1) immediately reposition to the left lateral position, 2) recheck vital signs, and 3) perform fetal heart sound monitoring.
Caution
Oxygen administration (option 1) or leg elevation (option 2) may be supportive interventions, but they do not address the root cause (inferior vena cava compression). Emergency cesarean section (option 3) is not a necessary intervention in this case unless accompanied by other severe complications such as fetal distress. Keep in mind that the question asks for the "most appropriate immediate nursing intervention."