Why do contractions stop after a series of them in labor?

Why Contractions Stop After Multiple Consecutive Contractions

Contractions may cease after a prolonged series due to uterine muscle fatigue from inadequate rest periods between contractions, excessive oxytocin stimulation causing uterine hyperstimulation followed by exhaustion, or as a protective mechanism when uterine activity becomes excessive (tachysystole). 1

Physiologic Mechanisms of Contraction Cessation

Uterine Hyperstimulation and Exhaustion

• Excessive uterine activity—defined as more than 5 contractions in 10 minutes—can lead to uterine muscle fatigue and subsequent cessation of contractions. 2
• Oxytocin overdosage causes hyperstimulation with strong (hypertonic) or prolonged (tetanic) contractions, or a resting tone of 15-20 mm H₂O or more between contractions, which can lead to uterine dysfunction. 1
• When uterine contractions become too powerful or frequent, the myometrium may become refractory and stop contracting effectively as a protective response. 1

Inadequate Recovery Time Between Contractions

• The uterine muscle requires adequate rest periods between contractions to maintain effective contractility throughout labor. 3
• Contractions with abnormal shapes—specifically those with prolonged fall-to-rise (F:R) ratios greater than 1.64 seconds—are associated with poor labor progress and may precede contraction cessation. 4
• Ischemia during isometric uterine contractions activates nociceptors, and prolonged ischemia without adequate reperfusion periods can impair subsequent contractile function. 5

Clinical Recognition and Management

Identifying the Problem

• If contractions stop after a series of strong contractions, immediately assess whether hyperstimulation occurred by reviewing the contraction frequency and intensity. 2, 1
• Evidence of hyperstimulation requiring intervention occurs in approximately 19-20% of augmented labors. 6
• Monitor for resting uterine tone elevation, which indicates inadequate relaxation between contractions. 1

Immediate Management Steps

• If oxytocin is being administered, discontinue the infusion immediately when contractions cease after hyperstimulation, as oxytocic stimulation will wane quickly. 1
• Administer oxygen to the mother and evaluate both maternal and fetal status. 1
• Position the patient in left lateral decubitus to optimize uterine blood flow and allow uterine recovery. 7

Restarting Contractions Safely

• After uterine rest, if contractions do not resume spontaneously and labor augmentation is still indicated, restart oxytocin at a lower dose (1-2 mU/min) and increase gradually in increments of no more than 1-2 mU/min. 1
• The goal is to achieve a contraction pattern similar to normal labor (no more than 5 contractions per 10 minutes) with adequate rest periods between contractions. 2, 1
• Frequent monitoring of fetal heart rate, resting uterine tone, and contraction frequency, duration, and force is essential. 1

Common Pitfalls to Avoid

• Do not assume that more frequent or stronger contractions will accelerate labor progress—excessive stimulation leads to uterine dysfunction and contraction cessation. 1, 4
• Avoid continuing oxytocin infusion when contractions become tetanic or when resting tone remains elevated, as this will worsen uterine exhaustion. 1
• Do not restart oxytocin at the same dose that caused hyperstimulation; always reduce the dose and titrate more slowly. 1
• External tocodynamometry does not provide information about contraction strength, so clinical assessment and consideration of intrauterine pressure monitoring may be needed in cases of suspected hyperstimulation. 3, 6

Underlying Causes Beyond Hyperstimulation

• Inadequate uterine activity may be the primary problem rather than hyperstimulation, particularly in cases of labor dystocia. 8, 3
• Other factors contributing to contraction cessation include cephalopelvic disproportion, fetal malposition, maternal obesity, and excessive neuraxial anesthesia. 7
• Uterine overdistention from multiple pregnancy or polyhydramnios can impair effective contractions. 7