Uterine Tachysystole

The terms tachysystole, hypertonus, and hyperstimulation can all be used to refer to excessive uterine activity (contractions) during labor and delivery. Exact definitions for these terms vary; some consider only the frequency of contractions, while others take into account intensity, duration, resting tone between contractions, and/or the impact on the fetus. For the sake of simplicity, we will use the term “uterine tachysystole” throughout this article in reference to any sort of excessive uterine activity during labor and delivery.

Tachysystole deprives a fetus of oxygen and occasionally leads to an emergency complication known as uterine rupture. Some of the most serious long-term outcomes for the baby include hypoxic-ischemic encephalopathy (HIE), cerebral palsy (CP), and seizure disorders.

Uterine tachysystole occurs more frequently in women who have been given synthetic prostaglandins (such as Cytotec) or oxytocin (such as Pitocin). These are medications that doctors sometimes prescribe to induce or augment labor, although Cytotec has not been FDA-approved for this use, and Pitocin should only be given when medically necessary. The risk of tachysystole increases with higher doses of these drugs and is especially high when both drugs are administered together. Research has indicated that administering synthetic prostaglandins increases uterine sensitivity to oxytocin.

When the uterus contracts, the supply of oxygenated blood to the placenta, and ultimately the baby, is temporarily constricted. Babies can withstand a certain degree of diminished oxygenation during labor and delivery, but if contractions are too strong, last too long, or occur too frequently, or there is little or no rest in between, this can lead to a dangerous level of oxygen deprivation. Tachysystole can also occasionally lead to uterine rupture; this is an emergency complication that can result in severe maternal blood loss, birth asphyxia, and fetal acidosis. Infants who have experienced excessive uterine activity and/or uterine rupture may develop conditions such as hypoxic-ischemic encephalopathy (HIE), cerebral palsy (CP), and seizure disorders.

If there are signs of tachysystole or fetal distress (oxygen deprivation), clinicians should cease the administration of labor-enhancing drugs. Even if the infant’s heart rate appears to be normal, doctors should still immediately lower the dosage or stop administration entirely when a woman shows signs of tachysystole. It is possible that the situation will become more severe very quickly.

Treatments for tachysystole and fetal oxygen deprivation include placing the mother in the left lateral position, giving her oxygen, and increasing her IV fluids. Sometimes, additional medications can be given for fetal resuscitation. In some cases – especially if there is uterine rupture – an emergency C-section is necessary in order to prevent permanent harm to the fetus.

When physicians use labor-enhancing drugs, they must carefully monitor the fetus for signs of distress and be prepared to promptly respond if tachysystole occurs.