Clinical Review

A reasoned plan to manage a persistent Category-II FHR tracing

OBG Manag. 2011 December;23(12):30-49

	Hear Dr. Miller outline a rational approach to electronic fetal heart rate monitoring

When intrapartum fetal heart-rate monitoring reveals a persistent
Category-II tracing, you don’t have to linger in limbo—you can respond
in a systematic way

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IN THIS ARTICLE

3-tier fetal heart-rate classification
Decision model for management of intrapartum fetal heart rate

References

1. Macones GA, Hankins GD, Spong CY, Hauth J, Moore T. The 2008 National Institute of Child Health and Human Development workshop report on electronic fetal monitoring: update on definitions interpretation, and research guidelines. Obstet Gynecol. 2008;112(3):661-666.

2. American College of Obstetricians and Gynecologists. ACOG Practice Bulletin number 106: Intrapartum fetal heart rate monitoring: nomenclature interpretation, and general management principles. Obstet Gynecol. 2009;114(1):192-202.

3. American College of Obstetricians and Gynecologists. ACOG Practice Bulletin No. 116: Management of intrapartum fetal heart rate tracings. Obstet Gynecol. 2010;116(5):1232-1240.

4. Barbieri RL. Stop staring at that Category-II fetal heart-rate tracing…and do something instead to improve fetal status! OBG Manage. 2011;23(4):6-9.

5. Simpson KR, James DC. Efficacy of intrauterine resuscitation techniques in improving fetal oxygen status during labor. Obstet Gynecol. 2005;105(6):1362-1368.

6. Miller DA. Intrapartum fetal heart rate definitions and interpretation: evolving consensus. Clin Obstet Gynecol. 2011;54(1):16-21.

7. Miller DA. Intrapartum fetal heart monitoring: a standardized approach to management. Clin Obstet Gynecol. 2011;54(1):22-27.

8. To Err is Human: Building a Safer Health System. Kohn LT Corrigan JM, Donaldson MS, eds. Committee on Quality of Health Care in America. Institute of Medicine. Washington, DC: National Academy of Sciences;1999:14.

9. Pettker CM, Thung SF, Norwitz ER, et al. Impact of a comprehensive patient safety strategy on obstetric adverse events. Am J Obstet Gynecol. 2009;200(5):492.e1-8.

10. Clark SL, Belfort MA, Dildy GA, Meyers JA. Reducing obstetric litigation through alterations in practice patterns. Obstet Gynecol. 2008;112(6):1279-1283.

11. MacLennan A. A template for defining a causal relation between acute intrapartum events and cerebral palsy: International consensus statement. BMJ. 1999;319(7216):1054-1059.

12. American College of Obstetricians and Gynecologists. Neonatal Encephalopathy and Cerebral Palsy: Defining the Pathogenesis and Pathophysiology. Washington DC: American College of Obstetricians and Gynecologists; 2003.

13. Nelson KB, Dambrosia JM, Ting TY, Grether JK. Uncertain value of electronic fetal monitoring in predicting cerebral palsy. N Engl J Med. 1996;334(10):613-618.

14. Freeman RK, Nageotte MP. Comments on American College of Obstetricians and Gynecologists Practice Bulletin No. 106. Am J Obstet Gynecol. 2010;202(5):411-412.

15. Parer JT, King T, Flanders S, Fox M, Kilpatrick SJ. Fetal acidemia and electronic fetal heart rate patterns: is there evidence of an association? J Matern Fetal Neonatal Med. 2006;19(5):289-294.

RELATED ARTICLES

Stop staring at that Category-II fetal heart-rate tracing…
Robert L. Barbieri, MD (Editorial, April 2011)
Guidelines on fetal monitoring aim to codify normal, abnormal FHR
Robert L. Barbieri, MD (Editorial, October 2008)

CASE An uncertain interlude during labor

An obstetrician checks on her laboring patient, only to discover that the fetal heart-rate (FHR) tracing has moved from Category I, a normal classification, into Category II—a gray zone. The OB decides to be proactive, not simply to wait for the tracing to return to normal. She has the patient move from a supine to a lateral position, provides oxygen, and administers a bolus of 500 to 1,000 mL of lactated Ringer’s solution over 20 minutes.

The tracing remains in Category II.

What should the OB do next?

When a fetal heart-rate tracing remains in Category II despite well-considered conservative corrective measures, a reasoned, rather than passive, approach is recommended.In 2008, the National Institute of Child Health and Human Development proposed a three-tier classification system for electronic FHR tracings (TABLE 1).¹ Tracings in Category I are considered normal and can be managed routinely.^1-3 Category-III tracings are considered abnormal and require additional attention; if corrective measures do not result in improvement, rapid delivery usually is warranted.^1-3 Category II includes all FHR tracings that do not fit into either of the other categories. Because Category II encompasses such a wide range of FHR tracings, there are many options for management.

TABLE 1

3-tier fetal heart-rate classification system

Category	Description
I	Fetal heart-rate (FHR) tracings include all of the following: baseline rate is 110–160 bpm baseline FHR variability is moderate accelerations are present or absent late or variable decelerations are absent early decelerations are present or absent
II	Includes all FHR tracings not included in Category I or Category III
III	FHR tracings include: absent baseline FHR variability plus: sinusoidal pattern
Source: Adapted from Macones GA, et al.¹

If the case described above sounds familiar, it may be that you read Editor in Chief Dr. Robert L. Barbieri’s editorial on Category-II FHR tracings in the April 2011 issue of OBG Management.⁴ That essay described a number of common conservative corrective measures applicable for Category-II tracings, including the three interventions the OB performed.

Other measures:

reduce or stop infusion of oxytocin
discontinue cervical ripening agents
consider administering a tocolytic, such as terbutaline, if tachysystole is present or if uterine contractions are prolonged or coupled
consider the option of amnioinfusion if variable decelerations are present.^4,5

Systematic review of the oxygen pathway, from the environment to the fetus (maternal lungs, heart, vasculature, uterus, placenta, and umbilical cord), can facilitate recollection of all of these measures. In addition, a simplified “A-B-C-D” approach to the management of a Category-II FHR tracing is helpful (TABLES 2 and 3):

Assess the oxygen pathway
Begin conservative corrective measures
Clear obstacles to rapid delivery
Determine decision-to-delivery time.^6,7

TABLE 2

Conservative corrective measures to improve fetal oxygenation

	“A” Assess oxygen pathway	“B” Begin corrective measures if indicated
Lungs	Airway and breathing	Supplemental oxygen (10 L) using a tight-fitting, non-rebreather face mask for at least 15 minutes
Heart	Heart rate and rhythm	Position changes IV fluid bolus (500–1,000 cc of isotonic fluid over 20 min) Correct hypotension
Vasculature	Blood pressure Volume status
Uterus	Contraction strength Contraction frequency Baseline uterine tone Exclude uterine rupture	Stop or reduce uterine stimulants (oxytocin, prostaglandin) Consider uterine relaxant (terbutaline)
Placenta	Placental separation Bleeding vasa previa
Cord	Vaginal exam Exclude cord prolapse	Consider amnioinfusion
Courtesy of David A. Miller, MD

As the obstetrician in the opening scenario knows all too well, conservative corrective measures do not always transform FHR tracings from Category II to Category I. In fact, it is extremely common for a Category-II tracing to remain in Category II despite every conservative corrective measure in the book. This article presents a practical, systematic, standardized approach to the management of a persistent Category-II FHR tracing.

TABLE 3

Steps involved in preparing for delivery

	“C” Clear obstacles to rapid delivery	“D” Determine decision-to-delivery time
Facility	Operating room availability Equipment	Facility response time
Staff	Notify: Obstetrician Surgical assistant Anesthesiologist Neonatologist Pediatrician Nursing staff	Consider staff: Availability Training Experience
Mother	Informed consent Anesthesia options Laboratory tests Blood products Intravenous access Urinary catheter Abdominal prep Transfer to OR	Surgical considerations (prior abdominal or uterine surgery) Medical considerations (obesity, hypertension, diabetes, SLE) Obstetric considerations (parity, pelvimetry, placental location)
Fetus	Confirm: Estimated fetal weight Gestational age Presentation Position	Consider factors such as: Estimated fetal weight Gestational age Presentation Position
Labor	Confirm adequate monitoring of uterine contractions	Consider factors such as: Arrest disorder Protracted labor Remote from delivery Poor expulsive efforts
Courtesy of David A. Miller, MD

CASE Continued

When the OB’s preliminary interventions fail to nudge the FHR tracing back to Category I, she stops oxytocin and administers terbutaline. She even tries amnioinfusion. Still, the FHR tracing remains in Category II.