Effect of intrapartum use of oxytocin on estimated blood loss and hematocrit change at vaginal delivery.

We hypothesized that exogenous oxytocin given for labor induction or augmentation results in a greater blood loss at vaginal delivery compared with spontaneous labor. Second, we theorized that duration of exposure, and maximum or final dosage of oxytocin, would be positively correlated with blood loss. We retrospectively studied records of 111 women undergoing labor induction or augmentation by oxytocin infusion along with those of 76 women who had spontaneous labor. The outcomes evaluated included clinically estimated blood loss (EBL), and a change of hematocrit from admission to postpartum. These were further compared to duration and dosage of oxytocin infused. A combination of chi-square and analysis of variance were used to compare the study group with the controls. Regression analysis was used to evaluate possible relationships within the study group. The demographics of the study group who received oxytocin were similar to those of the control group, with the exception of the percent who received an epidural (77% versus 29%, p < 0.0001) and length of labor (381 versus 277 min, p < 0.001). There was no demonstrated relationship between oxytocin use and EBL or hematocrit change. Within the study group of 111 patients, there was a statistically significant increase in EBL (p < 0.01) and hematocrit change (p < 0.0003) with increasing maximum dose of oxytocin. In addition, hematocrit change was greater with an increase in both duration (p < 0.001) and final dose of oxytocin (p < 0.0003). No relationship was demonstrated between exogenous oxytocin administration and increased blood loss, in a group of patients matched for variables other than spontaneous or oxytocin exposed labors. However, among those patients who received oxytocin, there was a correlation between amount of oxytocin exposure and blood loss. The initial hypothesis compared means between the two groups; however, the latter hypothesis sought to correlate increased exposure to oxytocin with increasing blood loss as measured by duration, maximum, and final dose.