Electronic fetal monitoring (EFM) is a popular technology used to establish fetal well-being. Despite its widespread use, the terminology used to describe patterns seen on the monitor has not been consistent until recently. In 1997, the National Institute of Child Health and Human Development (NICHD) Research Planning Workshop published guidelines for interpretation of fetal tracings. This publication was the culmination of 2 years of work by a panel of experts in the field of fetal monitoring and was endorsed in 2005 by both the American College of Obstetricians and Gynecologists (ACOG) and the Association of Women’s Health, Obstetric and Neonatal Nurses (AWHONN). In 2008, ACOG, NICHD, and the Society for Maternal-Fetal Medicine reviewed and updated the definitions for fetal heart rate patterns, interpretation, and research recommendations. Following is a summary of the terminology definitions and assumptions found in the 2008 NICHD workshop report. Normal values for arterial umbilical cord gas values and indications of acidosis are defined in the Table.A 3-tier Fetal Heart Rate Interpretation system has been recommended as follows:Data from Macones GA, Hankins GDV, Spong CY, Hauth J, Moore T. The 2008 National Institute of Child Health and Human Development workshop report on electronic fetal monitoring. Obstet Gynecol. 2008;112:661-666 and American College of Obstetricians and Gynecologists. Intrapartum fetal heart rate monitoring: nomenclature, interpretation, and general management principles. ACOG Practice Bulletin No. 106. Washington, DC: American College of Obstetricians and Gynecologists; 2009.We encourage readers to examine each strip in the case presentation and make a personal interpretation of the findings before advancing to the expert interpretation provided.A 29-year-old gravida 1 para 0 women at 401/7 weeks’ gestation with diet-controlled gestational diabetes presented with newly diagnosed polyhydramnios. Her prenatal care was notable for a 100-g glucose tolerance test that had elevated 1-, 2-, and 3-hour blood glucose values, thus meeting the criteria for gestational diabetes. Her gestational diabetes was subsequently well controlled with lifestyle and diet modifications. The remainder of her medical and surgical histories were unremarkable. An estimated fetal weight performed 1 week before presentation was 3,475 g (59th percentile for gestational age).On presentation, she denied vaginal bleeding, loss of fluids, contractions, or fever and noted active fetal movement. She had no sick contacts at home. Her blood glucose on arrival measured 92 mg/dL (5.11 mmol/L). Induction of labor was recommended because of the new finding of polyhydramnios. Because of an unfavorable Bishop score, vaginal misoprostol was used for cervical ripening.After serial misoprostol administration, spontaneous rupture of membranes occurred. The patient progressed into latent labor and was started on oxytocin for augmentation. Twenty-six hours after initiation of labor induction, the maternal heart rate became tachycardic, ranging from 100 to 120 beats per minute. The fetal tracing (red) with maternal continuous heart rate monitoring (purple) is displayed in Fig 1.Findings from EFM strip 1 are as follows:One hour later, the patient was found to have an axillary temperature of 39.38°C (102.9°F). Shortly after developing a fever, the fetal (red) and maternal (purple) EFM tracing in Fig 2 is obtained.Findings from EFM strip 2 are as follows:Chorioamnionitis is a polymicrobial infection, most commonly associated with Enterobacteriaceae and cervical and vaginal flora such as group B Streptococcus that are transferred into the uterine cavity and infect products of conception. The diagnosis requires the presence of maternal fever as well as 2 of the following conditions: maternal leukocytosis (>15,000/μL [15 × 109/L]), maternal tachycardia (>100 beats per minute), uterine tenderness, and/or foul odor of the amniotic fluid. (1) This patient met the criteria of fever, maternal tachycardia, and fetal tachycardia. Initiation of intravenous ampicillin and gentamicin provided broad antimicrobial coverage, with the goal of preventing further maternal and fetal complications, such as sepsis, neonatal pneumonia, and meningitis. Additionally, administration of acetaminophen has the potential to reduce fetal tachycardia, thereby decreasing fetal stress. (2) Definitive treatment of chorioamnionitis is ultimately delivery.Three hours later, the fetal (red) and maternal (purple) EFM tracing shown in Fig 3 is obtained.Findings from EFM strip 3 are as follows:Recurrent late decelerations raise the concern for fetal acidosis. The goal at this point is to incorporate different interventions to increase uteroplacental perfusion. These maneuvers include maternal lateral repositioning, discontinuing oxytocin to decrease uterine contraction frequency and intensity, providing supplemental oxygen, and administering intravenous fluids. The late decelerations resolved after implementation of these maneuvers.Three hours later, the fetal (red) and maternal (purple) EFM shown in Fig 4 is obtained.Findings from EFM strip 4 are as follows:The patient was reexamined and found to have cervical expansion of 8 cm, with minimal cervical change from her last examination. Furthermore, her cervix was progressively more edematous. Oxytocin augmentation was warranted for the protraction disorder, but recurrent late decelerations were again noted with oxytocin augmentation, which precluded administration. Persistent late decelerations on FHR tracings raise the possibility for fetal acidemia and have been associated with neonatal encephalopathy, cerebral palsy, and neonatal acidosis. (3) Given the persistent category II tracing, chorioamnionitis, and the inability to augment with oxytocin, cesarean delivery was recommended.A liveborn female infant was delivered from the right occipital transverse position with a loose double nuchal cord. The infant weighed 3.34 kg, with Apgar scores of 8 and 9 at 1 and 5 minutes, respectively. The NICU team was present for the delivery because of the chorioamnionitis. Immediately after delivery, the infant was vigorous with spontaneous cry. Septic evaluation revealed an elevated white blood cell count of 18,500/μL (18.5 × 109/L), but no left shift or bandemia was seen on the differential count and she had negative blood cultures. The infant received empiric antibiotic treatment but otherwise had an uncomplicated immediate neonatal course.The incidence of chorioamnionitis is 2% to 4% in term deliveries, with a substantially higher incidence in preterm deliveries. Furthermore, the risk of infection has been found to be as high as 12% in patients who initially labor but ultimately have a cesarean delivery. (4) Risk factors associated with chorioamnionitis include prolonged labor, prolonged membrane rupture, repeated cervical examinations, meconium-stained amniotic fluid, a history of chorioamnionitis, nulliparity, and positive group B Streptococcus status. This patient’s risk factors included protracted labor and prolonged rupture of membranes.Another important consideration in making clinical decisions in the setting of infection is the duration of elapsed time from the time of chorioamnionitis diagnosis. While there is no threshold limit for delivery in the setting of chorioamnionitis, the maternal and fetal statuses need be interpreted in the appropriate context. Rouse et al (4) demonstrated an association of increased duration of labor once criteria for chorioamnionitis have been met with adverse maternal and fetal outcomes. Adverse maternal outcomes include increased risk for blood transfusion, uterine atony, septic pelvic thrombophlebitis, cesarean delivery, cellulitis, prolonged hospitalization and pelvic abscess. Fetal risks include neonatal sepsis, pneumonia, and meningitis. In addition, use of intrapartum antibiotics has been shown to decrease the risk of fetal adverse outcomes. (5)Due to the persistent category II tracing in the setting of chorioamnionitis and fetal intolerance of oxytocin augmentation, ongoing expectant management was not recommended. In this case, a cesarean delivery was the appropriate intervention, ultimately resulting in a viable and healthy infant as well as an uncomplicated neonatal and maternal postpartum course.