Chapter 15: Fetal Assessment During Labor

The systematic assessment of the fetus during labor is critical for maintaining adequate oxygen supply and promoting health after birth, especially since labor presents a period of significant physiological stress. Current practice often relies on electronic fetal monitoring (EFM), used in over 80% of labors in the United States, to visualize fetal heart rate (FHR) patterns and uterine contractions (UC). The interpretation of EFM tracings uses a three-tier system: Category I tracings are normal and predict a standard fetal acid-base status, characterized by a baseline FHR between 110–160 beats per minute (bpm) and moderate variability. Category II tracings are indeterminate and require continuous vigilance, encompassing characteristics like minimal or marked variability, or baseline rates falling into tachycardia (greater than 160 bpm) or bradycardia (lesser than 110 bpm). Category III tracings are abnormal and signal fetal metabolic acidemia, demanding immediate intervention due to the presence of absent baseline variability combined with recurrent late or variable decelerations, bradycardia, or a sinusoidal pattern. Fetal monitoring can be achieved externally using an ultrasound transducer for FHR and a tocotransducer to measure contraction frequency and duration, or internally, which provides a more accurate assessment but necessitates ruptured membranes for the placement of a spiral electrode and an intrauterine pressure catheter (IUPC). Internal monitoring also allows for the calculation of Montevideo units (MVUs) to objectively measure contraction intensity. Intermittent auscultation (IA) is an alternative method recommended for low-risk women, promoting mobility and requiring the nurse to assess the counted FHR and rhythm between, during, and after contractions, though it does not provide a permanent visual record of variability. Characteristic FHR patterns include accelerations, which are abrupt, temporary increases that indicate the absence of metabolic acidemia. Decelerations are categorized based on their relation to UCs: Early decelerations mirror the contraction and are benign, caused by transient fetal head compression; Late decelerations occur after the contraction begins, stemming from transient hypoxemia due to uteroplacental insufficiency; and Variable decelerations are defined by their abrupt U, V, or W shape, caused by umbilical cord compression. Prolonged decelerations, lasting longer than 2 minutes but lesser than 10 minutes, require immediate notification of the obstetric provider and intervention. Nursing management focuses on intrauterine resuscitation, which includes changing maternal position, increasing intravenous fluid rates, and administering supplemental oxygen to improve fetal oxygenation. Specific interventions include amnioinfusion to relieve recurrent variable decelerations by cushioning the umbilical cord in cases of low amniotic fluid, or tocolytic therapy to inhibit excessive uterine activity. Additional assessments, such as fetal scalp stimulation to elicit an FHR acceleration, aid in evaluating fetal acid-base balance. Nurses are legally responsible for accurate interpretation and timely, complete documentation using standardized terminology.