What is the immediate management of uterine hyperstimulation (prolonged uterine contractions) during labour?

Immediate Management of Uterine Hyperstimulation During Labor

If uterine hyperstimulation occurs during labor, immediately discontinue oxytocin (if being administered), reposition the patient to lateral position, administer supplemental oxygen, and increase IV fluid rate; if fetal heart rate abnormalities persist despite these measures, administer subcutaneous terbutaline 0.25 mg for acute tocolysis. 1, 2

Initial Resuscitative Measures

Stop all uterotonic agents immediately if oxytocin or prostaglandins are being administered, as continuing stimulation with abnormal fetal heart patterns risks worsening uteroplacental insufficiency and progressive fetal acidemia. 1, 3

Implement intrauterine resuscitation measures:

• Reposition to left lateral position to improve uteroplacental blood flow 1
• Administer supplemental oxygen via face mask 1
• Increase IV fluid rate to optimize maternal intravascular volume 1
• Assess contraction pattern by palpation (hypercontractility can be evaluated successfully by simple palpation unless obesity prevents it) 1

Definition and Recognition

Uterine hyperstimulation is now termed tachysystole: more than 5 contractions in a 10-minute period, averaged over a 30-minute window, qualified by the presence or absence of fetal heart rate decelerations. 1 The term "hyperstimulation" has been formally abandoned in favor of this more precise terminology. 1

Pharmacologic Tocolysis When Conservative Measures Fail

If fetal heart rate abnormalities persist 5-10 minutes after discontinuing oxytocin and implementing resuscitative measures, administer acute tocolysis:

First-Line Tocolytic Agent

• Subcutaneous terbutaline 0.25 mg is the most effective intervention, with resolution time significantly shorter than oxytocin discontinuation alone (0% persistence at 15 minutes versus 53% with discontinuation alone). 2 This approach allows for more rapid resolution without requiring complete cessation of labor progress. 2

Alternative Tocolytic Agents

Nitroglycerin can be considered when terbutaline is contraindicated or unavailable:

• Administer sublingual nitroglycerin 400-800 mcg or IV nitroglycerin 50-100 mcg bolus for immediate uterine relaxation 4
• Particularly effective for prostaglandin-induced hyperstimulation when removal of the agent (e.g., PROPESS) has not resolved the pattern 4

Magnesium sulfate is a third-line option:

• 4-6 gram IV loading dose over 20 minutes decreases contraction frequency while maintaining amplitude 5
• Less rapid onset than terbutaline or nitroglycerin but may be useful when beta-agonists are contraindicated 5

Critical Assessment for Underlying Pathology

While managing the acute hyperstimulation, simultaneously assess for cephalopelvic disproportion (CPD), as uterotonic stimulation is absolutely contraindicated if CPD is present or cannot be excluded. 1, 6

Examine for signs of CPD:

• Excessive molding without descent (differentiate molding from true descent via serial suprapubic palpation of the fetal skull base) 1, 7
• Marked asynclitism or deflexion of the fetal head 1
• Fetal malposition (occiput posterior or transverse) 1, 7
• Lack of fetal descent despite adequate contractions 1, 7

Decision Algorithm After Resolution

Once tachysystole resolves and fetal heart rate normalizes:

1. If CPD is identified or cannot be excluded with reasonable certainty, proceed to cesarean delivery rather than resuming oxytocin, as the risks of maternal and fetal trauma are too great. 1, 6

2. If CPD is definitively ruled out and labor progress was adequate before hyperstimulation, oxytocin may be cautiously restarted at a lower dose with slow titration in small increments. 1

3. If at advanced dilation (≥8-9 cm) without CPD, expectant management with serial cervical examinations is preferred over immediate oxytocin resumption. 6

Common Pitfalls to Avoid

• Do not continue oxytocin during tachysystole even at reduced rates—complete discontinuation is mandatory until the pattern resolves. 1, 3
• Do not rely solely on external tocodynamometry to assess contraction adequacy; clinical palpation is equally or more reliable unless obesity prevents it. 1
• Do not confuse molding with descent—use suprapubic palpation of the fetal skull base to confirm true descent. 1, 7
• Do not delay tocolytic administration if fetal heart rate abnormalities persist beyond 5-10 minutes of conservative measures, as this risks progressive fetal acidemia. 3, 2

Monitoring After Intervention

Continue continuous electronic fetal monitoring to assess for:

• Resolution of tachysystole (return to ≤5 contractions per 10 minutes) 1
• Normalization of fetal heart rate pattern (return of moderate variability, resolution of decelerations) 1
• Adequate uterine resting tone between contractions 1