Objective: To identify the effect of spinal anesthesia on the success rate of external cephalic version after 36 weeks' gestation.
Methods: Women with singleton breech presentations after 36 weeks' gestation were offered enrollment. Those who agreed were randomized to receive spinal anesthesia or no anesthesia. Up to four attempts were made using ultrasound surveillance. External cephalic version was terminated with patient discomfort or fetal heart decelerations. Statistical analysis based on intent-to-treat was performed using chi2, Student t tests, and multivariate analysis. Sample size projection based on 20% difference in success rate from a baseline of 50% indicated a need for 50 women in each group.
Results: One hundred two women were entered in the study from October 1993 to August 1997. There were no differences between groups in parity, maternal age, amniotic fluid index, gestational age, birth weight, placental location, type of breech presentation, maternal weight, or gestational age at delivery. Forty-four external cephalic versions were successful. Fifty (49%) women received spinal anesthesia, and 52 (51%) did not; there was no difference in the overall success rate between groups (44% spinal versus 42% no spinal). Spontaneous version occurred before external cephalic version was attempted in four patients in the spinal group (after the spinal was given) and one patient in the no-spinal group. These patients were included in the analysis.
Conclusion: Spinal anesthesia does not increase the external cephalic version success rate in singleton pregnancies with breech presentations after 36 weeks' gestation.