Category I: FHR tracings are normal
Criteria include all of the following:
• Baseline rate: 110-160 beats/min
• Baseline FHR variability: moderate
• Late or variable decelerations: absent
• Early decelerations: present or absent
• Accelerations: present or absent
Interpretation: strongly predictive of normal fetal acid-base status at time of observation
Action: monitoring in a routine manner, with no specific action required
Category II: FHR tracings are indeterminate
These include all FHR tracings not categorized as category I or III, and may represent an appreciable fraction of those encountered in clinical care.
Interpretation: not predictive of abnormal fetal acid-base status
Action: evaluation and continued surveillance and reevaluation, taking into account theentire associated clinical circumstances
Category III: FHR tracings are abnormal
Criteria include absent baseline FHR variability and any of the following:
• Recurrent late decelerations
• Recurrent variable decelerations
• Bradycardia
• Sinusoidal pattern
Interpretation: associated with abnormal fetal acid-base status at time of observation;requires prompt evaluation
Action: expeditious intrauterine resuscitation to resolve the abnormal FHR pattern; if trac-ing does not resolve with these measures, prompt delivery should take place.
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Chapter 16 l Intrapartum Fetal Monitoring
180
FHR
100
50
UC 0
| Early Decelerations—head compression | 1 minute | |
| 180 | ||
| FHR | ||
| 100 | ||
| 50 | ||
| UC | ||
| 0 | 1 minute | |
| Late Decelerations—uteroplacental insufficiency | ||
180 FHR
100
50
UC 0
| Variable Decelerations—umbilical cord compression | 1 minute | |
Figure I-16-3. Electronic Fetal Monitor Decelerations
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INTRAUTERINE RESUSCITATION
Decrease uterine contractions: Turn off any IV oxytocin infusion or administer terbutaline0.25 mg subcutaneously to enhance intervillous placental blood flow.
Augment IV fluid volume: Infuse the parturient with a 500 mL bolus of intravenous normalsaline rapidly to enhance uteroplacental infusion.
Administer high-flow oxygen: Give the parturient 8–10 L of oxygen by facemask to increasedelivery of maternal oxygen to the placenta.
Amniofusion is useful for eliminating or reducing the severity of variable decelerations.
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USMLE Step 2 l Obstetrics
Change position: Removing the parturient from the supine position decreases inferior venacava compression and enhances cardiac return, thus cardiac output to the placenta. Turning the parturient from one lateral position to the other may relieve any umbilical cord compression that may be present.
Vaginal examination: Perform a digital vaginal examination to rule out possible prolapsedumbilical cord.
Scalp stimulation: Perform a digital scalp stimulation observing for accelerations, which wouldbe reassuring of fetal condition.
FETAL pH ASSESSMENT
Intrapartum—fetal scalp blood pH may be used in labor if the EFM strip is equivocal.Prerequisites include cervical dilation, ruptured membranes, and adequate descent of the fetal head. Contraindications are suspected fetal blood dyscrasia. A small, shallow fetal scalp incision is made resulting in capillary bleeding. The blood is collected in a heparinized capillary tube and sent to the laboratory for blood gas analysis. Normal fetal pH is >7.20. This procedure is seldom performed today.
Postpartum—umbilical artery blood pH is used to confirm fetal status at delivery. It involvesobtaining both umbilical cord venous and arterial samples. Arterial Pco2 and base deficit values are higher than venous, but pH and Po2 are lower. Normal fetal pH is >7.20.
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