A 26-year-old woman, gravida 2 para 1, at 35 weeks gestation comes to the labor and delivery department due to regular, painful contractions over the past 3 hours. The patient has had no prenatal care during this pregnancy. She has no chronic medical conditions, and her only surgery was a low transverse cesarean delivery 2 years ago. Her cervix on admission is 7 cm dilated and 100% effaced with the fetal head at +2 station. Fetal heart rate tracing on admission is category 1. Epidural analgesia is administered, and the patient has pain relief from the contractions. Rupture of membranes results in bright-red amniotic fluid. Blood pressure is 130/80 mm Hg and pulse is 112/min. Current fetal monitoring is as seen in the exhibit. Which of the following is the most likely cause of this fetal heart rate tracing?

Question

A 26-year-old woman, gravida 2 para 1, at 35 weeks gestation comes to the labor and delivery department due to regular, painful contractions over the past 3 hours.  The patient has had no prenatal care during this pregnancy.  She has no chronic medical conditions, and her only surgery was a low transverse cesarean delivery 2 years ago.  Her cervix on admission is 7 cm dilated and 100% effaced with the fetal head at +2 station.  Fetal heart rate tracing on admission is category 1.  Epidural analgesia is administered, and the patient has pain relief from the contractions.  Rupture of membranes results in bright-red amniotic fluid.  Blood pressure is 130/80 mm Hg and pulse is 112/min.  Current fetal monitoring is as seen in the exhibit.  Which of the following is the most likely cause of this fetal heart rate tracing?

Quizplus · Accepted Answer

11ec25c8_da30_ca37_bc81_97dc5b9c96f7_MD0003_00 Fetal heart rate (FHR) monitoring in labor assesses fetal oxygenation and metabolic status to prevent fetal morbidity and mortality. A category I FHR tracing (reassuring) has a low risk of fetal hypoxemia and acidemia and is managed expectantly. In contrast, a category III FHR tracing has an increased risk of fetal compromise and requires urgent intervention to prevent fetal injury and demise. This patient has a sinusoidal fetal heart rate tracing, defined as a smooth, wave-like oscillation (ie, rolling line), with fixed amplitude (5-15/min) and frequency (3-5 cycles/min). Sinusoidal tracings are a category III tracing and are considered ominous because they are associated with severe fetal anemia, suggested in this patient with likely fetal blood loss from ruptured vasa previa (eg, bright-red amniotic fluid). Due to rapid fetal exsanguination and deterioration, this patient requires urgent cesarean delivery. smooth, wave-like oscillation vasa previa (Choice B) Intraamniotic infection (chorioamnionitis) is usually associated with prolonged membrane rupture. FHR monitoring typically shows fetal tachycardia (>160/min) due to maternal fever and increased sympathetic drive. fetal tachycardia (Choices C and E) Oligohydramnios (amniotic fluid index ?5 cm) may cause variable decelerations due to umbilical cord compression. Variable decelerations occur because, as the uterus contracts, the umbilical cord is compressed, initially affecting the thin-walled umbilical vein and causing a transient reflex rise in the FHR. Continued cord compression eventually occludes the thick-walled umbilical artery, causing a rapid increase in blood pressure and subsequent abrupt drop in heart rate (ie, parasympathetic response). As the contraction releases, there is an equally rapid return to baseline. variable decelerations (Choice D) Preterm (<37 week) gestation may be associated with an increased FHR baseline, reduced variability, and lower-amplitude accelerations. It does not cause sinusoidal rhythms. Educational objective: Sinusoidal fetal heart rate tracings are typically associated with severe fetal anemia. They are a category III tracing that reflects an increased risk of fetal compromise (eg, hypoxemia, acidemia) and requires urgent cesarean delivery. References: Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour. (http://www.ncbi.nlm.nih.gov/pubmed/28157275) Massive fetomaternal hemorrhage as a cause of severe fetal anemia. (http://www.ncbi.nlm.nih.gov/pubmed/29341561) Antepartum high-frequency fetal heart rate sinusoidal rhythm: computerized detection and fetal anemia. (http://www.ncbi.nlm.nih.gov/pubmed/19114268)

A 26-Year-Old Woman, Gravida 2 Para 1, at 35 Weeks