Oxytocin Regimen for Labor Augmentation, Labor Progression, and Perinatal Outcomes

To the Editor: We read with great interest the article by Zhang et al1 on oxytocin regimens in labor (low-dose oxytocin compared with higher doses). Both the source of the data, the “Consortium on Safe Labor,” and the strong conclusions might exert a relevant influence on clinical practice: “High-dose oxytocin regimen…is associated with a shorter duration of first-stage of labor for all parities without increasing the cesarean delivery rate or adversely affecting perinatal outcomes.”1 We believe there are methodologic questions and explanations of the results that might benefit from additional information and discussion by the authors. This is an intra-regimens analysis, and the value for odds is defined by group with the lowest dosage. We appreciated the positive message to consider a “high oxytocin regimen” a maximum dosage of 20 milliunits per minute, which is well below some aggressive “individualized” regimens observed in clinical practice. However, which are the criteria to titrate oxytocin? We believe that the very criteria of stratification in high-dose and low-dose based on infused milliunits and not on uterine activity is questionable. Oxytocin has a tremendous individual variability,2 especially when infusion is started from a dilatation of 1 cm to the acceleration part of the active phase of labor,3 and reported doses in the three arms widely overlap, as reported in Table 2 of the article.1 From this point of view, the aim to compare low-dose and high-dose might be challenged, and the results might be considered as an overall outcome in oxytocin accelerating term labors with fetuses in vertex presentation. The second step was to look at outcome. The reported evidence in the whole cohort of nulliparous women at term was surgical abdominal deliveries: 15.6%, operative vaginal deliveries: 16%, shoulder dystocia: 1.2%, third–fourthdegree perineal lacerations: 5.9%, and neonatal intensive care unit admission: 6.8%. In our region, Lombardy, in 2008, women with cesarean deliveries in Robson Class 1 less than 8% yielded an overall rate of cesarean delivery below 25%. Those with cesarean deliveries in Robson Class 1 greater than 14% yielded an overall cesarean delivery rate of less than 35%.4 We believe that, to understand the relationship between oxytocin intervention and outcome, the case mix at recruitment should be available to the reader. If these outcome data belong to Robson Class 1 deliveries (normal pregnancies, term, spontaneous labor at term, vertex presentation), there should be some concern about the level of cesarean and operative deliveries. Unfortunately, no information is provided on the prevalence of maternal or fetal risk at delivery (late-onset preeclampsia, gestational diabetes, intrauterine growth restriction, macrosomic fetuses). Not even maternal body mass index or fetal weights are reported. Similar lack of information does not help us understand the effects of oxytocin on postpartum hemorrhage and fetal distress. The prevalence of postpartum hemorrhage—minor, major, or severe—is not reported. Maternal complications related to postpartum hemorrhage are embedded in a composite index that ranges from abruptio in labor, to postpartum hemorrhage, to transfusions, to hysterectomy. We can suppose that postpartum hemorrhages occurred in approximately 1 of every 10 deliveries, but their severity is undeterminable. The same goes for the composite index of neonatal outcome, which ranges from neonatal death to transient tachypnea, with a prevalence on the whole cohort of nulliparous women of 3.1% (one in two fetuses admitted to the neonatal intensive care unit). We believe that, without additional information on 1) a case-mix of this cohort and 2) maternal and neonatal composite indices, it is almost impossible to sort out which poor outcome could be ascribed to oxytocin labor augmentation and which to preexisting abnormal maternal and fetal conditions. In its present form, this article seems to support the idea that oxytocin, whatever the dose, achieves 48 –78 minutes worth of reduction of the length of labor with an identical obstetric outcome, depending on the unknown case-mix of the cohort. This might be good news for the attending physician.2 We doubt that it is that good for the mother and the neonate. Care and support in labor might achieve similar results in duration of labor without exposing women to the iatrogenic effects of an unnecessary medical intervention.5–7