Outcomes after internal versus external tocodynamometry for monitoring labor. Augmentation of labor: does internal tocography result in better obstetric outcome than external tocography? Induction of labour: does internal tocography result in better obstetric outcome than external tocography.
It has been hypothesized that internal tocodynamometry, as compared with external monitoring, may provide a more accurate assessment of contractions and thus improve the ability to adjust the dose of oxytocin effectively, resulting in fewer operative deliveries and less fetal distress. However, few data are available to test this hypothesis.
                We performed a randomized, controlled trial in six hospitals in The Netherlands to compare internal tocodynamometry with external monitoring of uterine activity in women for whom induced or augmented labor was required. The primary outcome was the rate of operative deliveries, including both cesarean sections and instrumented vaginal deliveries. Secondary outcomes included the use of antibiotics during labor, time from randomization to delivery, and adverse neonatal outcomes (defined as any of the following: an Apgar score at 5 minutes of less than 7, umbilical-artery pH of less than 7.05, and neonatal hospital stay of longer than 48 hours).
                We randomly assigned 1456 women to either internal tocodynamometry (734) or external monitoring (722). The operative-delivery rate was 31.3% in the internal-tocodynamometry group and 29.6% in the external-monitoring group (relative risk with internal monitoring, 1.1; 95% confidence interval [CI], 0.91 to 1.2). Secondary outcomes did not differ significantly between the two groups. The rate of adverse neonatal outcomes was 14.3% with internal monitoring and 15.0% with external monitoring (relative risk, 0.95; 95% CI, 0.74 to 1.2). No serious adverse events associated with use of the intrauterine pressure catheter were reported.
                Internal tocodynamometry during induced or augmented labor, as compared with external monitoring, did not significantly reduce the rate of operative deliveries or of adverse neonatal outcomes. (Current Controlled Trials number, ISRCTN13667534; Netherlands Trial number, NTR285.)
                2010 Massachusetts Medical Society Labor was augmented in 250 patients for slow progress. These women were randomized to have uterine contractions recorded by either an external tocotransducer or an intrauterine catheter. Oxytocin was titrated to achieve an optimal frequency of contractions of six to seven every 15 minutes in each group; additional information on active contraction area profiles was available for those patients who had an intrauterine catheter. There was no statistically significant difference between the groups in the length of the post-augmentation period. The mean maximum dose of oxytocin was 11.1 mU/minute in the external tocography group and 11.0 mU/minute in the internal tocography group. Evidence of uterine hyperstimulation requiring temporary reduction of the oxytocin dose occurred in 19 and 20.2% of the patients in the external and internal tocography groups, respectively. Cesarean delivery was necessary in 12.6 and 16.9% of patients in the external and internal tocography groups, respectively, which is a nonsignificant difference. The incidence of low Apgar scores in the neonates and admission to neonatal intensive care was similar in both groups. The incidence of poor Apgar scores was not different between those who had transient hyperstimulation and those who had no hyperstimulation. In the management of augmented labor, monitoring of uterine contractions by intrauterine pressure catheters did not confer any advantage over tocography by external transducers. A prospective randomized study was undertaken to evaluate the benefit of intrauterine catheters in induced labour. Two hundred and thirty nine women who had induced labour were studied. The patients in one group had intrauterine catheters inserted and oxytocin was titrated to achieve the 75th percentile of uterine activity observed in spontaneous normal labour according to parity. Contractions were assessed by external tocography in the other group and oxytocin was titrated to achieve 6 to 7 contractions per 15 minutes each lasting > 40 seconds. Mean maximum dose of oxytocin, mode of delivery, Apgar score < 7 at 5 minutes, cord arterial blood pH < 7.15 and admission to neonatal intensive care unit did not differ significantly in the 2 groups. In conclusion, women who had intrauterine catheters did not have a shorter duration of labour, lower dose of oxytocin, fewer operative deliveries or fewer babies in poor condition at birth compared with those who had external tocography in induced labour.
This review found no differences between the two types of monitoring (internal or external tocodynamometry) for any of the maternal or neonatal outcomes. Given that this review is based on three studies (N = 1945 women) of moderate quality, there is insufficient evidence to recommend the use of one form of tocodynamometry over another for women where intravenous oxytocin was administered for induction or augmentation of labour.