Internal Tocodynamometry Disappoints in Large Trial


Major Finding: Thirty-one percent of women in the internal-tocodynamometry group and thirty percent in the external-monitoring group required operative delivery, a nonsignificant difference.

Data Source: A multicenter trial of 1,456 women.

Disclosures: None reported.

Internal tocodynamometry during induced or augmented labor failed to reduce the rate of operative deliveries compared with external monitoring of uterine contractions, according to a report.

Nor did internal tocodynamometry improve the rate of adverse neonatal outcomes, the use of analgesia, the use of antibiotics, or duration of labor in a multicenter trial comparing the two approaches, according to Jannet J.H. Bakker of the Academic Medical Center, Amsterdam, and her associates.

Internal tocodynamometry is advocated by professional obstetric societies because it “is thought to quantify the frequency, duration, and magnitude of uterine activity more accurately” than external monitoring. This in turn is assumed to allow better adjustment of oxytocin infusion and improved interpretation of fetal heart-rate patterns.

“However, clinical data to support such hypotheses are limited, and recommendations are based on expert opinion” in the absence of definitive data, the investigators noted.

Only three small clinical trials have compared the two techniques, and “the small samples in these trials resulted in limited power to detect differences and in wide confidence intervals around estimated risk reductions,” they said.

Ms. Bakker and her colleagues assessed 1,456 women who delivered at six hospitals in the Netherlands over a 4-year period. All the women had singleton, term pregnancies and received oxytocin for induction or augmentation of labor. They were randomized to internal tocodynamometry (734 patients) or external monitoring (722 patients).

The primary outcome was the rate of operative delivery. In all, 230 women (31%) in the internal-tocodynamometry group and 214 (30%) in the external-monitoring group required operative delivery, a nonsignificant difference, the researchers said (N. Engl. J. Med. 2010;362:306-13).

The rates of secondary outcomes also were similar between the two groups. These included adverse neonatal outcomes, use of antibiotics during labor, use of analgesia, and total amount of oxytocin used.

Internal tocodynamometry carries serious risks, “including placental or fetal-vessel damage, infection, and anaphylactic reaction. We did not observe any complications of internal monitoring in our study, but it was not powered to detect these events,” which are estimated to occur in up to 1 in 300 deliveries.

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