Effect of external cephalic version at term on fetal circulation

OBJECTIVE: We sought to investigate the subclinical effect of external ceph alic version on fetal circulation. STUDY DESIGN: A prospective observational study was conducted on 136 subjec ts who had external cephalic version at or beyond 36 weeks of gestation wit hout clinical complication. Doppler ultrasonographic studies of the umbilic al and middle cerebral circulations were performed before and after the ext ernal cephalic version. The following Doppler indexes were measured: (1) th e pulsatility index of the umbilical artery, which represents disturbance o f placental circulation, and (2) the pulsatility index of the fetal middle cerebral artery, which represents fetal response. The Wilcoxon signed rank test was used for ail statistical analyses. RESULTS: There was no significant difference in pulsatility index of the um bilical artery before and after external cephalic version (P=.674). There w as a statistically significant reduction in the pulsatility index of the mi ddle cerebral artery after external cephalic version (P=.043), and this dif ference existed only among multiparous women (P=.029), among those in whom the external cephalic version was considered to be difficult (P=.038), and when the placenta was posteriorly located (P=.028). The reduction in pulsat ility index was not related to whether the external cephalic version was su ccessful. In all cases the Doppler indexes remained within the normal range s, and there were no associated fetal complications. CONCLUSION: External cephalic version was not associated with any significa nt disturbance of placental resistance to blood flow. Conversely, external cephalic version was associated with a significant reduction in the pulsati lity index of the middle cerebral circulation, especially among the multipa rous women, after a difficult procedure or in those with a posterior placen ta. This probably represents a normal fetal physiologic response to manipul ation of the fetal head.