Author's Response

We thank Dr. Wax for his interest in our article. In their study, Wax et al evaluated 38 cases and 114 matched controls, and found that the frequencies of operative vaginal and cesarean delivery in cases did not differ from those of controls (3/38 versus 1/114, p = 0.56 and 4/38 versus 8/114, p = 0.51, respectively). Nevertheless, we suspect that this study is underpowered to compare the mode of delivery between these two groups. A sample size analyses shows that in order to detect a difference between cesarean section (CS) rate of 10.5% (study group) and 7% (control group), > 1000 women in each group are required to achieve a power of 80% with a significance level of 0.05. Similar analysis for instrumental delivery rates (7.8% versus 0.8%) shows that 158 women in each group are needed.

In our study, we compared 96 cases and 192 matched controls. The rate of intrapartum CS in the study group was 19.8% (19/96), which was 3.2 times higher than that in the controls (12/192, 6.25%, p < 0.001). Furthermore, we claimed that the combined analysis of CS and instrumental delivery is important for the correct evaluation of deviations from normal labor. If we use the report of Wax et al, this combined rate in their study group (7/38, 18.4%) was higher than in controls (9/114, 7.8%). This is almost statistically significant (p = 0.067, OR = 2.63; 95% CI, 0.90-7.6), and should alert the reader to the understanding that a larger study is required.

Our study was in agreement with other reports,[1] [2] [3] although we did not find higher rates of nonreassuring fetal heart rate patterns in our study group. We speculated that the higher CS rate in the study group could be explained by the higher mean gestational age at delivery and birth rate or the rate of macrosomia in this group. Additionally, we showed that higher rates of labor dystocia and malpresentations could be a part of that. We thought that the longer interval from ECV to delivery in women who had CS was also contributory (this might explain the higher gestational age at delivery and birth rate). Because labor induction may increase the CS rate we do not recommend it for this population, other than for accepted obstetrical indications.

We believe that it is important to explain the possibility of increased risk of intrapartum CS after successful ECV to women that undergo this procedure. We also welcome prospective studies addressing this issue of delivery following successful ECV.

REFERENCES

• 1a Lau T K, Lo K W. Rogers M. Pregnancy outcome after successful external cephalic version for breech presentation.  Am J Obstet Gynecol . 1997;  176 218-223
• 2a Stine L E, Phelan J P, Wallace R, Eglinton G S, van Dorsten J P, Schifrin B S. Update on external cephalic version performed at term.  Obstet Gynecol . 1985;  65 642-646
• 3a Laros Jr R K, Flanagan T A, Wallace R, Kilpatrick S J. Management of term breech presentation: a protocol of external cephalic version and selective trail of labor.  Am J Obstet Gynecol . 1995;  172 1916-1923