Does intra-uterine environment influence fetal head-position preference? A comparison between breech and cephalic presentation

Background: Cephalic fetuses have increasing lateralised head-position near term. Aim: Is this development affected by breech presentation? Subjects and methods. Fetal head-position was studied longitudinally in 13 healthy fetuses in breech presentation and 10 healthy fetuses in cephalic presentation by means of real-time ultrasound. Recordings were obtained weekly from 33 weeks gestational age until birth. Results: As in previous research, a significant (p=0.045) decrease in midline head-position was found for the cephalic fetuses with advancing gestational age. The development of a lateralised head-position preference was clearly less outspoken in the breech fetuses when compared to the cephalic ones, especially after 36 weeks gestational age. Furthermore, as cephalic fetuses showed a preference for a right-sided head-position, breech fetuses that did show a lateralised head-position did not have a clear preference for left or right. Our data show an association between the orientation of the fetal vertebral column and head-position predominance in the group of cephalic fetuses, which complies with Previc's left-otolithic dominance theory. No association could be detected between fetal head shape and head-position preference. Conclusions: This study shows evidence that development in head laterality is influenced by the breech presentation. The discussion addresses possible explanations for the differences we found between the breech and cephalic fetuses. © 2004 Elsevier Ireland Ltd. All rights reserved