In many birth injury cases, a great deal of time is involved in evaluating the electronic fetal monitor information and determing what should have been done by the labor and delivery team in response to the developing data. The big picture that should always be kept in mind is that the electronic fetal monitor is a real time print-out of data that tells the L & D team the current acid-base status of the baby. What follows is an excerpt from the current ICSI Management of Labor Guidelines from May 2009 related to interpretation of the electronic fetal monitor tracings. It is provided here so that the reader can put meaning to the terminology in the labor and deliver records when reviewing them for appropriateness of care.
- FRH Pattern Is Predictive of Normal Acid-Base Status?
All obstetrical nurses, nurse midwives, and physicians must achieve competence and confidence in fetal heart rate monitoring and FHR pattern analysis. Based on careful review of the available options, a three-tier system for the categorization of FHR patterns is recommended (see Table developed by the guideline committee in Annotation #80 in the original guideline document). Fetal heart rate tracing patterns can provide information on the current acid-base status of the fetus but cannot predict the development of cerebral palsy. Categorization of the FHR tracing evaluates the fetus at that point in time; tracing patterns can and will change [R].
- Deceleration is delayed in timing, onset-to-nadir if the deceleration is 30 seconds or greater, and there is a gradual decrease and return to baseline.
- Onset, nadir and recovery mirror the beginning, peak, and ending of the contraction.
- Abrupt decrease in FHR with onset to nadir of deceleration reached in less than 30 seconds, decrease in FHR is 15 seconds or greater and less than two minutes in duration.
- Fluctuations in the FHR baseline over a 10-minute window, accelerations and decelerations are not included in the range.
- Absent - amplitude range is undetectable.
- Minimal - amplitude range is between 2 beats per minutes (bpm) and 5 bpm.
- Moderate - amplitude range is between 6 bpm and 25 bpm.
- Marked - amplitude range is greater than 25 bpm.
- Decelerations that occur with 50% or greater of uterine contractions in any 20-minute window.
- Cyclic, smooth, sine wavelike undulating pattern in the FHR baseline frequency cycle of 3-5 per minute that persists for 20 minutes or longer.
- Assessment and Remedial Techniques
A persistently Category II or Category III FHR tracing requires evaluation of the possible causes. Initial evaluation and treatment may include:
- Discontinuation of any labor stimulating agent
- Cervical examination to assess for umbilical cord prolapse or rapid cervical dilation or descent of the fetal head
- Changing maternal position to the left or right lateral recumbent position, reducing compression of the vena cava and improving uteroplacental blood flow
- Monitoring maternal blood pressure level for evidence of hypotension, especially in those with regional anesthesia (if present, treatment with ephedrine or phenylephrine may be warranted)
- Assessment of patient for uterine hyperstimulation by evaluating uterine contraction frequency and duration
- Amnioinfusion - indications for therapeutic amnioinfusion include repetitive severe variable decelerations and prolonged decelerations [A]. Amnioinfusion for thick meconium is no longer recommended [R].
- Further FHR Assessment Predictive of Normal Acid-Base
Obtain obstetrical or surgical consultation or referral where needed to plan for operative delivery if the FHR pattern is Category III. Consider contacting a neonatology team to plan for possible neonatal intervention.
Scalp stimulation or vibroacoustic testing may be used for further fetal assessment. A 15-beat-per-minute rise in FHR lasting 15 seconds from the beginning to the end of the acceleration in response to scalp stimulation or to vibration or sound is predictive of normal fetal acid-base status. If the scalp stimulation test or vibroacoustic test response is abnormal, immediate delivery is indicated.
Other tests to assess fetal acid-base status may be helpful if available. This includes fetal scalp sampling for PH. A scalp pH greater than 7.19 is a positive result [D], [M].
However, proper FHR pattern interpretation and the response to scalp stimulation or vibroacoustic stimulation can allow the clinician to detect tracings predictive of abnormal feta acid-base status.
Knowledge of the fetal oxygen saturation is not associated with a reduction in the rate of Caesarean delivery or with improvement in the condition of the newborn [A]."