A 36-year-old woman, gravida 1 para 0, at 36 weeks gestation is undergoing induction of labor due to preeclampsia with severe features. The patient is receiving a magnesium sulfate infusion for seizure prophylaxis and an oxytocin infusion for labor augmentation. She had spontaneous rupture of membranes with clear fluid 4 hours ago. The patient had epidural anesthesia placed due to increasingly painful contractions and now has adequate pain relief. She has a history of hypothyroidism that has been poorly controlled during pregnancy. Temperature is 39.4 C (103 F), blood pressure is 150/90 mm Hg, and pulse is 114/min. Fetal heart rate tracing is shown below: Which of the following is the most likely cause of this patient's fetal heart rate tracing?

Question

A 36-year-old woman, gravida 1 para 0, at 36 weeks gestation is undergoing induction of labor due to preeclampsia with severe features.  The patient is receiving a magnesium sulfate infusion for seizure prophylaxis and an oxytocin infusion for labor augmentation.  She had spontaneous rupture of membranes with clear fluid 4 hours ago.  The patient had epidural anesthesia placed due to increasingly painful contractions and now has adequate pain relief.  She has a history of hypothyroidism that has been poorly controlled during pregnancy.  Temperature is 39.4 C (103 F), blood pressure is 150/90 mm Hg, and pulse is 114/min.  Fetal heart rate tracing is shown below:  Which of the following is the most likely cause of this patient's fetal heart rate tracing?

Quizplus · Accepted Answer

11ec25c8_d29f_fdec_bc81_055ae8c1864e_MD0003_00 This fetal heart rate tracing shows fetal tachycardia, a fetal heart rate with a baseline >160/min. Fetal tachycardia is associated with medication side effects (eg, beta agonists) and fetal hyperthyroidism; however, the most common cause (particularly during labor) is maternal fever from intraamniotic infection (IAI) (chorioamnionitis), as the temperature elevation and increased metabolic demand create an elevated fetal heart rate. Fetal tachycardia IAI occurs due to polymicrobial vaginal bacteria ascending into the uterus during labor. Patients have maternal fever ≥39.0 C (in the absence of another clear cause), leukocytosis (>15,000/mm³), and/or purulent amniotic fluid. The risk of developing IAI increases as labor progresses and after membrane rupture (as in this patient). Treatment is with antipyretic therapy, broad-spectrum antibiotics, and delivery (eg, induction, augmentation) to prevent fetal morbidity (eg, sepsis, cerebral palsy) and mortality. (Choice A) Poorly controlled maternal hypothyroidism is associated with pregnancy complications (eg, preeclampsia, impaired fetal cognitive development). However, congenital hypothyroidism is typically caused by fetal thyroid dysgenesis (not maternal thyroid dysfunction), and fetal monitoring is usually normal or has signs of metabolic slowing (eg, fetal bradycardia <110/min). (Choice B) Epidural anesthesia blocks the sympathetic drive and may cause a decrease in maternal blood pressure, resulting in a transient reduction in placental blood flow. This typically results in fetal bradycardia and/or late decelerations. (Choice C) Magnesium sulfate prevents seizures (eclampsia) in patients with preeclampsia with severe features (as in this patient). Fetal heart rate tracings typically reveal a transient decrease in variability due to CNS depression. variability (Choice E) Uterine tachysystole (>5 contractions in 10 minutes) may be associated with late fetal decelerations because there is a transient decrease in placental perfusion during contractions and inadequate recovery time between contractions. This patient has had only 4 contractions in 10 minutes. late fetal decelerations Educational objective: Fetal tachycardia is defined as a fetal heart rate baseline >160/min and is commonly associated with maternal fever due to intraamniotic infection (chorioamnionitis). References: Accuracy of signs of clinical chorioamnionitis in the term parturient. (http://www.ncbi.nlm.nih.gov/pubmed/23154669) Evidence for the clinical management of chorioamnionitis. (http://www.ncbi.nlm.nih.gov/pubmed/21962477) Chorioamnionitis and neonatal outcome in preterm infants: a clinical overview. (http://www.ncbi.nlm.nih.gov/pubmed/26135227) Fever and pregnancy. (http://www.ncbi.nlm.nih.gov/pubmed/27386764)

A 36-Year-Old Woman, Gravida 1 Para 0, at 36 Weeks