Oxytocin augmentation of second-trimester abortion: safe or hazardous?

The role of oxytocin in augmenting the uterine activity of second-trimester instillation abortions is controversial. To evaluate the efficacy and safety of oxytocin augmentation, we studied 10,013 women who underwent hypertonic saline instillation procedures and 1,241 women who underwent prostaglandin F2a (PGF2a) instillation procedures in the United States in the period 1971 through 1975. Data were obtained through the Joint Program for the Study of Abortion under the auspices of the Center for Disease Control, a multi-center, prospective, cohort study. We found that concurrent administration of oxytocin was associated with a significantly shorter instillation-to-abortion time for hypertonic saline, but with a significantly longer time for PGF2a. For hypertonic saline, use of concurrent oxytocin did not affect either the success rate or the major complication rate; however, it did not affect the specific type of complication that occurred. For PGF2a, use of concurrent oxytocin was associated with a lower success rate and a higher major complication rate than when PGF2a was used alone; however, the relatively small number of observations and limitations in our study design may have affected our results. When we compared the 2 main abortifacients, even when we controlled for concurrent oxytocin augmentation, unaugmented PGF2a had higher major complication rates than hypertonic saline.