In December 2003, ACOG, the American College of Obstetricians and Gynecologists, issued a Practice Bulletin (#49) for its members, in which it recommended the use of intrauterine monitoring of contractions during augmentation or induction of labor in select patients, such as those suffering from obesity. There were some obstetrical organizations who were recommending the routine use of internal contraction monitoring to assess contractions more accurately.
Of course, the intent behind such recommendations was ostensibly to provide the attending obstetrician with better/more accurate information with which to make clinical decisions regarding the need for an operative birth (i.e. C-section or instrument assisted birth), dosing effectively with oxytocin nad avoidance of complications in such labor situations – the common end-result being to improve fetal and maternal outcomes in such deliveries.
On the other side of the risk/benefit equation, it is only common sense that the use of an internal monitor would increase certain risks – the medical literature speaks of the most common of these as being placental and/or fetal vessel damage, infection and anaphylactic reaction.
A new study by the Academic Medical Center in Amsterdam, led by Jannet J. H. Bakker, MSc, and reported by The New England Journal of Medicine on January 28, 2010 - NEJM — Outcomes after Internal versus External Tocodynamometry for Monitoring Labor raises serious questions about the use of such monitoring when one applies a science-based risk/benefit analysis.
The study reports in pertinent part:
In summary, the results of our trial do not support the routine use of internal tocodynamometry for monitoring contractions in women with induced or augmented labor.
In this multicenter, randomized trial we found no significant difference in rates of operative delivery with internal tocodynamometry as compared with external monitoring of uterine contractions among women in whom oxytocin was used for induction or augmentation of labor. On the basis of the lower boundary of the confidence interval around the observed relative risk of the primary outcome, our data are plausibly consistent with no more than a 9% reduction and up to a 20% increase in the risk of operative delivery associated with internal tocodynamometry. For cesarean section alone, plausible results range from a 17% reduction in risk to a 30% increase in risk with internal tocodynamometry. These results are in concordance with those of three previous small trials that compared internal and external uterine monitoring (each including between 127 and 250 patients), all of which showed a nonsignificant increase in the frequency of cesarean sections in the internal-tocodynamometry group.
Our trial also showed no significant difference between the two types of monitoring in the rates of adverse neonatal outcomes, rates of use of analgesia or antibiotics, or time to delivery. Similarly, none of the earlier studies showed significant benefits in terms of other maternal or neonatal outcomes with the use of an intrauterine pressure catheter.
For a full review of the patient population, the limitations of the study, please refer to the NEJM article.