What Constitutes Fetal Distress?

July 6, 2011

With the experts unable to reach consensus, front-line clinicians must continue to rely on their own criteria and experience to decide when a fetus is in jeopardy. Here's how several of your colleagues make that call.

With the experts unable to reach consensus, front-line clinicians must continue to rely on their own criteria and experience to decide when a fetus is in jeopardy. Here's how several of your colleagues make that call.

Despite repeated efforts to define it and to create guidelines for its management, fetal distress remains mostly in the eye of the beholder. Four years ago this month, a committee of perinatologists and other experts convened by the National Institute of Child Health and Human Development (NICHHD) set out to develop standardized and rigorously unambiguous definitions for FHR terminology.

The committee, which met periodically for the next 19 months, found that it was rarely possible to determine from a dozen studies on the efficacy of fetal heart rate monitoring exactly what the authors used for definitions and quantification of the various patterns.1 (The ambiguity extends beyond defining one's terms to deciding what term one should use. "Fetal distress" has met with disfavor in recent years, and the American College of Obstetricians and Gynecologists now urges physicians to employ the more descriptive "nonreassuring fetal heart rate tracing." ACOG acknowledges, however, that the phrase fetal distress has been so commonly applied to abnormal intrapartum FHR patterns that it will be difficult to get obstetricians to abandon the term completely.2)

Despite these obstacles, the committee members did reach consensus on what a full description of an intrapartum FHR tracing should include, which tracing patterns most likely represented a well-oxygenated fetus, and which predicted current or impending asphyxia severe enough to put the fetus at grave risk. (See "Coming to terms with the terms," page 80.) However, they were less successful in determining the meaning of patterns which fell between those signifying a clearly compensated and a clearly compromised fetus, and eventually concluded that attempting to set guidelines for clinical management of FHR tracings at this juncture would be premature.

That decision has left the task of defining fetal distress squarely on the shoulders of those who've always had to make the tough call-the Ob/Gyns who pore over yards and yards of FHR strips, scrutinizing the peaks and troughs of intrapartum tracings in an attempt to distinguish the physiologically compensated fetus from the one in jeopardy of neurological or other damage, or even death. We asked several of those practitioners how they define fetal distress in their practices.

Here is what your colleagues said:
David E. Abel, MD, Morrisville, Vt-We don't use the term fetal distress. Rather, we have instituted a broad definition for a nonreassuring pattern: Decreased long-term variability, repetitive (or any suggestion of late) decelerations, a sinusoidal FHR pattern, or repetitive severe variations, beat to beat.

Leslie Breiten, MD, Binghamton, NY--Fetal distress to me is a FHR of <100 bpm for >60 seconds.

Timothy P. Canavan, MD, Lancaster, Pa--We define fetal distress as a deceleration of the fetal heart rate to 60 bpm for >2 minutes, unresponsive to medical management such as a change in maternal position, O2, or intravenous fluids, in the face of a medically compromised fetus or abnormal labor; or a deceleration =60 bpm for greater than 5 minutes, unresponsive to medical management, in a normal fetus and normal labor.

Joel Cohen, MD, Pleasanton, Calif--Fetal distress is fetal bradycardia that doesn't respond to intrauterine resuscitation attempts.

June Williams Colman, MD, Houston, Tex--We define fetal distress as the presence of late decelerations in >50% of the contractions in a 30-minute period, with decelerations not resolving with intrauterine resuscitation. Also, we believe there is fetal distress when there are deep variables >60 bpm below baseline, and they do not respond to resuscitation.

Robert Cowan, MD, Austin, Tex--Repetitive late decelerations or one prolonged fetal bradycardiac episode indicates fetal distress to us. We have the nurses call us when the FHR tracing shows repetitive, late decelerations; prolonged fetal bradycardia; or deep, variable decelerations.

Joseph H. Cutchin, Jr, MD, Salisbury, Md--To me, fetal distress is a term used by the legal profession after an obstetrician has a bad outcome. I have been practicing obstetrics for 30 years and I still do not know what fetal distress is, nor have I seen any studies that define it.

Mary S. David, MD, Dyersburg, Tenn--We define fetal stress and try to avoid distress. The nurse should call me if she is worried or if the FHR tracing shows severe variables, bradycardia, decreased variability, or late decelerations.

Robert Grover, MD, Bangor, Me--Fetal distress is repetitive severe decelerations (<60 bpm, >60 seconds); persistent fetal tachycardia (>160 bpm) with the loss of beat-to-beat variability; or persistent late deceleration and loss of variability. We've had instances of being called by overanxious or excessively worried nurses, and of not being called by those who are overconfident. We need some standardization to help prevent an increase in cesarean sections for fetal distress.

William Hahn, Jr, MD, Parma, Ohio--If the scalp pH is <7.20, the fetus is distressed. If the physician is unable to do a scalp pH, a tracing with the following represents fetal distress: Recurrent late decelerations with a loss of variability; bradycardia >10 minutes; and severe recurrent variable decelerations with loss of variability at baseline and slow recovery. The nurse is instructed to call us when she sees recurrent late decelerations, a loss of beat-to-beat variability, bradycardia, or severe variables.

Joseph Han, MD, Elgin, Ill--Fetal distress presents on a FHR tracing as significantly decreased variability with late decelerations; late recurrent decelerations; or recurrent and prolonged fetal bradycardia. There are too many false alarms with having criteria for nonreassuring patterns. Overall, however, it is better to be more attentive than to ignore true nonreassuring patterns.

John F. Huddleston, MD, Jacksonville, Fla--Fetal distress is a precarious fetal condition which if allowed to persist may lead to perinatal damage or death. The nurses call us when they see recurrent (occurring with =50% of contractions in a 20-minute window) late or severe variable decelerations, prolonged decelerations, or a nonreactive tracing initially persisting >20 minutes despite fetal acoustic stimulation.

Godwin Onyeike, MD, Staten Island, NY--Fetal distress is a term that has been used to predict fetal hypoxia, but I don't feel we should continue to use it. Non-reassuring FHR tracings is the more proper term. I ask the nurses to call me when they see a baseline bradycardia or tachycardia, decreased variability, or variable-to-late decelerations.

David B. Owens, MD, Overland Park, Kan--A FHR with persistent, true, late decelerations accompanied by loss of beat-to-beat variability and no reactivity-unresponsive to O2, a change in maternal position, or correction of low blood pressure; or persistent severe variables with loss of beat-to-beat variability. Severe variables and loss of beat-to-beat variability should prompt a call from the L&D nurse.

Wesley F. Prater, MD, Canton, Miss--Fetal distress occurs when the fetal heart rate is =120 bpm, or there is a loss of beat-to-beat variability at 36 weeks or later. The nurse should call when she sees a fetal heart rate tracing of =120 bpm, or decreased beat-to-beat variability in a pregnancy =36 weeks, unless it is due to analgesics.

Kevin D. Reilly, MD, Bronx, NY--We define fetal distress as an abnormal fetal heart rate tracing that is characterized by decreased variability; variable or late decelerations; tachycardial, bradycardial, or sinusoidal pattern; and is associated with a scalp pH <7.2. With residents and in-house supervising attendings, our policy is to notify the physician when any decelerations, tachycardia, bradycardia, decreased variability, or sinusoidal patterns occur. The problem is not so much in having a policy but rather in having the nurse recognize the subtle pattern abnormalities.

N.C. Sekharan, MD, Natches, Miss--Fetal distress presents as persistent, late decelerations that don't resolve with medical measures; severe variable decelerations; and severe fetal bradycardia with a sinusoidal pattern.

James E. Seltzer, DO, Woodstock, Ill--Fetal distress cannot be defined by electronic fetal monitoring alone, so we define it as an abnormal fetal heart tracing accompanied by documented evidence of fetal hypoxia, such as abnormal umbilical cord gases.

Sidney R. Sogolow, MD, Los Gatos, Calif--Fetal distress is evidence of deterioration in fetal condition which, left untreated, might lead to fetal compromise. The L&D nurse should call me with any findings that she feels fall under this definition.

Daniel R. Szekely, MD, Port Angeles, Wash--Fetal acidosis indicates fetal distress, and I want to be notified if the FHR tracing shows bradycardia <100 bpm on 2 or more occasions or tachycardia =180 bpm; absent beat-to-beat variability; sinusoidal pattern; or slow recovery from variable decelerations with a FHR strictly above 100 bpm. I also tell the nurses they should fax a tracing to me if they are just thinking that they should.

Patrick Urban, MD, Albuquerque, NM--Distress is indicated by prolonged bradycardia with a FHR <90 bpm for >60 seconds; = 3 consecutive repetitive late decelerations; and recurrent deep, severe variable deceleration lasting >60 seconds that are 60 bpm under baseline or reaching >60 bpm.

Donald P. Ward, MD, Austin, Tex--Fetal distress is continually confused with fetal intolerance to labor. The former exists when the obstetrician has concluded with reasonable certainty that some degree of fetal hypoxia is present and that sustained exposure to this condition is likely to result in irreversible tissue damage. Thus, it may be more appropriately termed obstetrician's distress over severely abnormal indicators.

References
1. National Institute of Child Health and Human Development Research Planning Workshop. Electronic fetal heart rate monitoring: research guidelines for interpretation. Am J Obstet Gynecol. 1997;177:1385-1390.

2. American College of Obstetricians and Gynecologists. Fetal heart rate patterns: monitoring, interpretation, and management. ACOG technical bulletin #207. Washington, DC: ACOG; 1995.

Coming to terms with the terms

While guidelines for interpreting a FHR tracing eluded participants in the National Institute of Child Health and Human Development Research Planning Workshops on electronic fetal heart rate monitoring, they did determine that a full description of a FHR tracing should include a qualitative and quantitative description of baseline rate, baseline FHR variability, the presence of accelerations, periodic or episodic decelerations, and changes or trends of FHR patterns over time.1They also defined the following terms:
Baseline FHR-approximate mean FHR rounded to increments of 5 bpm during a 10-minute segment, excluding periodic or episodic changes, periods of marked FHR variability, and segments of the baseline that differ by >25 bpm. In any 10-minute window, the minimum baseline duration must be at least 2 minutes or the baseline for that period is indeterminate.

Bradycardia-a baseline FHR <110 bpm.

Tachycardia-a baseline FHR >160 bpm.

Baseline FHR variability-fluctuations in the baseline FHR =2 cycles per minute. These fluctuations are irregular in amplitude and frequency, and are visually quantitated as the amplitude of the peak to the trough in beats per minute as follows: amplitude range undetectable, absent FHR variability; amplitude range greater than undetectable but = 5 bpm, minimal FHR variability; amplitude range 6 bpm to 25 bpm, moderate FHR variability; amplitude range >25 bpm, marked FHR variability.

Sinusoidal pattern-a smooth, sine wave-like pattern of regular frequency and amplitude; excluded from the definition of FHR variability.

Acceleration-a visually apparent, abrupt increase (defined as onset of acceleration to peak in <30 seconds) in FHR above the baseline. The increase is calculated from the most-recently determined portion of the baseline. The acme is 15 bpm above the baseline, and the acceleration lasts =15 seconds and <2 minutes from the onset to return to baseline.
Prolonged acceleration-=2 minutes and <10 minutes in duration. Acceleration of =10 minutes is a baseline change.

Late deceleration-a visually-apparent, gradual decrease (defined as onset of deceleration to nadir =30 seconds) and return to baseline FHR associated with a uterine contraction. The decrease is calculated from the most recently determined portion of the baseline. The deceleration is delayed in timing, with the nadir of the deceleration occurring after the peak on the contraction.

Early deceleration-a visually-apparent, gradual decrease (defined as onset of deceleration to nadir =30 seconds) and return to baseline FHR associated with a uterine contraction. The decrease is calculated from the most recently determined portion of the baseline. It is coincident in timing with the nadir of the deceleration occurring at the same time as the peak of the contraction. In most cases the onset, nadir, and recovery of the deceleration are coincident with the beginning, peak, and ending of the contraction, respectively.

Variable deceleration-a visually-apparent, abrupt decrease in FHR below the baseline. The decrease is calculated from the most recently determined portion of the baseline. The decrease in FHR below the baseline is =15 bpm, lasting =15 seconds and =2 minutes from onset to return to baseline.

Prolonged deceleration-a visually-apparent decrease in FHR below the baseline. The decrease from the baseline is =15 bpm, lasting =2 minutes, but <10 minutes from onset to return to baseline. Prolonged deceleration of =10 minutes is a baseline change.

Recurrent decelerations-tentatively defined as occurring with =50% of uterine contractions in any 20-minute segment.

Periodic patterns-FHR patterns associated with uterine contractions.

Episodic patterns-FHR patterns not associated with uterine contractions.

Reference
1. National Institute of Child Health and Human Development Research Planning Workshop. Electronic fetal heart rate monitoring: research guidelines for interpretation. Am J Obstet Gynecol. 1997;177:1385-1390.

The beat goes on . . .even when you're not there

The physician-participants in the NICHHD Research Planning Workshops, held in 1995 and 1996, expressed eager anticipation for the day when computer technology would not only help physicians and nurses quantify beat-to-beat variability but also track the amplitude range and frequency of long-term complexes.

While those applications are being developed, Ob/Gyns throughout the country are making the most of currently available technology. For instance, Michael Messina, MD, of Utica, Mich, already is using computer technology to aid him in assessing fetal heart rate tracings from his home. "We have central monitoring with modem remote capabilities. If the resident or nurse feels uncomfortable with a tracing, I can call in from home and review the real-time and historical strip on my home PC."

Daniel R. Szekely, MD, Port Angeles, Wash, makes use of less-sophisticated but equally valuable available technology. "I have a fax machine at home. I tell the nurses to fax a copy of any tracing of concern."