Strip of the Month

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 has been endorsed by both the American College of Obstetricians and Gynecologists (ACOG) and the Association of Women's Health, Obstetric and Neonatal Nurses (AWHONN). The terminology definitions and assumptions found in the NICHD publication form the basis for interpretation of the fetal tracings in this series and are summarized here. Normal values for arterial umbilical cord gas values and indications of acidosis are defined in the TableT1.Decelerations are tentatively called recurrent if they occur with ≥50% of uterine contractions in a 20-minute period.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 27-year-old G1 P0 woman presents to labor and delivery at 41+5 weeks’ gestation with complaints of vaginal bleeding with urination. Her prenatal course was uneventful. Past history is positive for exposure to lead (worked in India), bleeding in the first trimester with threatened abortion, and iron deficiency anemia. Vaginal examination reveals the cervix dilated 2 cm, 70% effaced, and at a −2 station. Uterine contractions are mild and irregular. The patient was scheduled for an induction for postterm dates later in the day. A fetal tracing is obtained at admission (Fig. 1).Findings on EFM Strip #1 are: Administration of intravenous fluids and oxygen are initiated. The nurse also attempts vibroacoustic stimulation (VAS) to elicit an acceleration of the FHR, but the attempt is unsuccessful. A well-oxygenated fetus responds to VAS by demonstrating an acceleration that is more than 15 beats/min above the baseline and lasting more than 15 seconds. Research has shown that this type of acceleration in response to stimulation correlates with a fetal blood pH of greater than 7.2. The absence of an acceleration does not diagnose acidemia, but approximately 40% of fetuses in this group have blood pH values less than 7.2 and always require further evaluation to rule out acidemia. The mother reports that she felt increased fetal movement this morning. The physician discusses the following plan of care with the patient and significant other: Start induction with oxytocin; monitor the fetus continuously to assess its ability to tolerate labor; and if the fetus does not demonstrate a reassuring FHR, consider a cesarean section. Approximately 1½ hours after admission, oxytocin administration is started at 1 MU/min and another tracing is obtained (Fig. 2).Findings on EFM Strip #2 are: All of the previously noted interventions are undertaken, and approximately 2½ hours later, another fetal tracing is obtained (Fig. 3).Findings on EFM Strip #3 are: Seventy minutes later, when the oxytocin administration is at 2 MU/min, another tracing is obtained (Fig. 4).Findings on EFT Strip #4 are: The previously noted interventions are successful in re-establishing a reassuring strip. For the next 3 hours, the labor continues, oxytocin is restarted, and the physician ruptures the patient's membranes, revealing meconium-stained fluid. The vaginal examination reveals the cervix to be dilated 2 to 3 cm. Approximately 1½ hours later, the cervix is 3 cm dilated, 100% effaced, and the presenting part is at a −1 station. A fetal scalp electrode is applied, and another tracing is obtained (Fig. 5).Findings of EFM Strip #5 are: After the previously noted interventions, the fetus recovers to a normal baseline with minimal variability. However, because of the recurrent prolonged deceleration pattern, postterm dates, and the fact that the patient is not likely to deliver vaginally for many hours, delivery by cesarean section is undertaken.Forty minutes later, a viable female infant is delivered by cesarean section with Apgar scores of 8 at 1 minute and 9 at 5 minutes. One nuchal cord is noted at delivery. Arterial cord gas values reveal a mild respiratory acidosis, which is consistent with the fetal heart rate changes.T2