When a fetal monitor shows late decelerations, what is the first action the nurse should take?

When late decelerations are observed on a fetal monitor, the first action the nurse should take is to position the patient in a left lateral position. This intervention is crucial because positioning the patient can help improve uteroplacental blood flow, which may be compromised. Late decelerations are typically associated with uterine compression or placental insufficiency, indicating a potential decrease in oxygen supply to the fetus. By placing the patient on her left side, it attempts to relieve any pressure on the umbilical cord or the uterus, thus enhancing fetal oxygenation and reducing or eliminating the late decelerations.

This maneuver is often a first-line response because it can be quickly enacted without requiring physician orders or extensive preparation. It is an effective and straightforward nursing intervention that addresses fetal well-being actively and promptly.