Fetal acoustic stimulation, an adjunct to external cephalic version: a blinded, randomized crossover study.

OBJECTIVE: Our purpose was to determine whether fetal acoustic stimulation can improve the chance of successful external cephalic version in patients at 36 to 38 weeks' gestation with fetal midline spine position.

STUDY DESIGN: A randomized, blinded crossover trial was performed. In this "N of 1" study, the patient served as her own control.

RESULTS: Twenty-six patients were enrolled in the study, and three were excluded due to engagement of the fetal breech. In the initial trial with fetal acoustic stimulation to the maternal abdomen, 12 of 12 (100%) changed position to spine lateral and 11 of 12 (92%) were successfully verted. In the control group (fetal acoustic stimulation to nurse's arm), none of 11 (0%) changed position to spine lateral and one of 11 (9%) were successfully verted (p < 0.0001). In the crossover trial eight of 10 (80%) of the original placebo (control) patients were successfully verted after fetal acoustic stimulation to the maternal abdomen and none of 1 (0%) from the original treatment group were successfully verted after placebo fetal acoustic stimulation (p < 0.0001). Combined data from the original and crossover trials indicates 19 of 22 (86%) successful versions after fetal acoustic stimulation to maternal abdomen compared with one of 12 (8%) that had successful external cephalic version after placebo fetal acoustic stimulation.

CONCLUSION: Fetal acoustic stimulation shifts fetal position to spine lateral, which increases successful version of fetuses with midline fetal spine presentations.