ABSTRACT
OBJECTIVE: Fetuses found to be in the breech presentation have limited motion of their lower limbs. The aim of this study was to test the hypothesis that bone speed of sound (SOS) would be lower in infants born after breech presentation than in those born after vertex presentation. STUDY DESIGN: We studied 127 singleton, appropriate for gestational age, term infants delivered by a scheduled cesarean delivery at approximately 38 weeks of gestation because of breech presentation or repeat elective cesarean section with vertex presentation. We used the Sunlight Omnisense 7000p device to measure axially transmitted SOS of the right tibia within the first 96 h of life. RESULT: Fifty-three infants studied (42%) were born by cesarean section after breech presentation compared to 74 vertex controls. Bone SOS was significantly lower in the breech presentation group, even after taking into account the effect of gender and parity (as well as gestational age at birth and birth weight). CONCLUSION: Bone SOS is lower in infants born after breech presentation than in those born after vertex presentation. We speculate that limited motion of lower limbs in fetuses found to be in the breech presentation leads to a decrease in bone mineralization and strength.
