Discontinuing Oxytocin During Active Labor Appears Largely Safe

NEW YORK (Reuters Health) – Routinely discontinuing oxytocin stimulation during active labor, and while electronic fetal monitoring is under way, significantly reduces the risks of uterine hyperstimulation and abnormal fetal heart rate, although it might lead to a small rise in C-sections, a clinical trial from Denmark shows.

Four meta-analyses have suggested that labor continues if oxytocin is stopped during active labor, “resulting in a lower risk of caesarean section for fetal indications secondary to uterine hyperstimulation,” researchers write in The BMJ. But researchers have questioned the quality of the studies that were analyzed.

“It is now up to clinicians worldwide to decide whether they find the current evidence (including this study) sufficient to routinely discontinue oxytocin stimulation in the active phase of induced labor,” lead author Dr. Sidsel Boie of Randers Regional Hospital told Reuters Health by email.

She and her colleagues conducted a randomized, double-blind, multi-center trial involving nearly 1,200 women at nine delivery wards in Denmark and one in the Netherlands, enrolled from 2016 to 2020. All participants were 18 or older, with a singleton live fetus with a cephalic presentation.

Oxytocin stimulation consisted of an intravenous infusion that started at 3.3 mIU/min and increased every 20 minutes by 3.3 mIU/min until regular contractions were achieved (three to five contractions every 10 minutes).

Participants were randomized when active labor was established, defined as ruptured membranes with complete effacement of the cervix, cervical dilatation of at least 6 cm, and at least three contractions every 10 minutes. After randomization, the infusion was replaced by the study medication: Either continued oxytocin at the standard concentration, or saline placebo.

All participants were continuously monitored with cardiotocography.

The difference in the rates of cesarean section in women who discontinued (16.6%) versus continued oxytocin (14.2%) was not statistically significant (relative risk, 1.17; 95% confidence interval, 0.90 to 1.53).

The discontinuation of oxytocin significantly reduced (P< 0.001 for all) the risks of uterine hyperstimulation (3.7% vs. 12.9%) and fetal heart-rate abnormalities (27.9% vs. 40.8%), but also lengthened labor (median from randomization to delivery, 282 vs. 201 min).

The smaller risks of uterine hyperstimulation and abnormal fetal heart rate patterns “may be important in settings where close observation of mother and fetus may be challenging owing to shortages of resources,” the authors suggest.

“It could be that cessation is not beneficial for every woman,” Dr. Boie said. “Perhaps the laboring woman with barely acceptable progression of labor despite maximal dosage of oxytocin stimulation would not benefit from discontinuation, but the woman who progresses rapidly after initiation of only a minimal dosage of the oxytocin infusion does not need continuous stimulation.”

She and her coauthors describe theirs as “the largest truly double blinded trial on discontinuation of oxytocin stimulation in the active phase of induced labour.”

They note that their findings vary from those of previous studies, “which suggested that oxytocin discontinuation significantly reduces the risk of caesarean section.” They point out, however, that most previous studies either were designed to measure duration of labor as the primary outcome or had such limitations as open-label administration or small sample sizes of 100-200 women.

Dr. Vincenzo Berghella, director of the Division of Maternal Fetal Medicine at Thomas Jefferson University, in Philadelphia, worked on one of the meta-analyses finding fewer C-sections with discontinued oxytocin.

He told Reuters Health by email that given the Danish findings, “My conclusion is probably that overall caesarean rate is not affected; certainly we cannot say discontinuation increases cesarean, as this is not significant in any study.”

In both his group’s 2017 meta-analysis and the Danish study, Dr. Berghella said, “discontinuation of oxytocin was associated with a decrease in uterine tachysystole – which is very important, since it is associated with non-reassuring fetal status. And discontinuation is consistently associated with an increase in the duration of the active phase of labor – this is also important, as longer labor eventually can be associated with more bleeding and infection.”

The bottom line, he concluded, is “it probably does not make much of a difference; I would consider stopping oxytocin if labor is progressing well, and there is no reason to ‘speed’ labor.”

The Danish findings, Dr. Berghella said, “confirm that if there are too many contractions (more than 3 in 10 min.) and the fetal heart rate is being affected by too many contractions, oxytocin should be safely stopped.”

SOURCE: https://bit.ly/2SeCZOK The BMJ, online April 14, 2021.

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