Strip of the Month: October 2011

Abstract

Electronic fetal monitoring (EFM) is a popular technology used to establish fetal well-being. Despite its widespread use, 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 Table 1.A three-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 Gynecocol. 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 28-year-old G2P1 woman at 38–3/7 weeks' gestation presents to labor and delivery in early labor desiring a trial of labor after cesarean section (TOLAC). She is currently contracting every 6 minutes, with intact membranes, and is admitted for augmentation of labor. She reports positive fetal movement and denies bleeding or leaking of fluid. Her history includes gestational diabetes (controlled by diet), a previous cesarean section for arrest of dilation at 3 cm, and a large-for-gestational age baby weighing 9 lb 8 oz. Her temperature is 36.8°C, heart rate is 78 beats/min, respiratory rate is 18 breaths/min, and blood pressure is 95/60 mm Hg. A cervical examination is deferred at this time. An initial FHR tracing is obtained shortly after admission (Fig. 1).Findings on EFM Strip #1 are: Over the next few hours, the patient receives early epidural analgesia and oxytocin therapy, and her contractions increase in intensity and frequency to every 2 minutes. Vital signs remain within normal limits, and she is afebrile. A cervical examination reveals 1 cm dilation, 70% effacement, and −2 station. Membranes are intact and oxytocin infusion is now at 10 MU/min. The FHR tracing remains a Category I, indicating a normal acid-base and a well-oxygenated fetus at this time. Four hours later, cervical examination shows 5 cm dilation, 80% effacement, and a floating station. A fetal tracing is obtained (Fig. 2).Findings on EFM Strip #2 are: Two hours later, results of a cervical examination document no changes, with 5 cm dilation and 80% effacement, but the station is now −2, allowing artificial rupture of the membranes. Clear fluid is noted. A fetal scalp electrode (FSE) and intrauterine pressure catheter (IUPC) are inserted to assess FHR variability more accurately and quantify uterine activity and intrauterine pressure. The associated tracing is seen in Figure 3.Findings on EFM Strip #3 are: Over the next hour, the FHR tracing remains a Category I, with recurrent early decelerations. Contractions continue every 2 minutes, with 180 MVUs. Maternal vital signs are within normal limits. The plan is to continue to monitor FHR and uterine activity and recheck the cervix in 2 hours to rule out an arrest of dilatation. However, the findings on the FHR tracing obtained 1 hour later (Fig. 4) prompt a change in plans.Findings on EFM Strip #4 are: Approximately 9 minutes later, a viable female infant weighing 3,620 kg is delivered by cesarean section with Apgar scores of 8 and 8 at 1 and 5 minutes, respectively. Cord gases indicate a mild respiratory acidosis (Table 2). Even though there was no evidence of a uterine rupture, the decision to deliver immediately was a good one and reflects a very efficient team that was well prepared to expedite the delivery of the infant within minutes of the prolonged deceleration.