Bone Abstracts

Animal studies suggest that fetal movements are key to healthy skeletal development, but evidence in humans is limited. Breech presentation occurs in 3% of term births and is associated with reduced fetal movement and higher incidence of hip dysplasias, but more general effects on bone development have not been explored.

Offspring whole body bone outcomes were measured using dual-energy X-ray absorptiometry (DXA) at mean(SD) 6(5) days after birth in 993 individuals (513 male) from the longitudinal Southampton Women’s Survey. Of these, 41 children (20 male) had a breech presentation at birth. To examine whether group differences were evident in later childhood, total body, hip and spine bone outcomes were examined by DXA at 4.12(0.06) years of age in 1015 individuals (524 male) of whom 39 (20 male) had been breech presentation.

Adjusting for maternal parity, social class, smoking, ethnicity, and offspring age at time of scan, infants with breech presentation had 11.0g lower neonatal total body bone mineral content (BMC; 95% CI −16.0g to −5.9g, P<0.001), 18.5 cm² lower bone area (BA; 95% CI −26.9 cm² to −10.2 cm², P<0.001) and 6.7g/ cm² lower bone mineral density (BMD; 95% CI −10.1g/cm² to −3.3g/cm², P=0.041). At four years, in similarly adjusted models breech presentation was associated with lower hip BMC (−5.3g, 95% CI −10.3g to 0.4g, P=0.036) and BA (−0.78 cm², 95%CI −1.40 cm² to −0.15 cm², P=0.015) but not BMD (P=0.466); there were no associations between breech presentation and total body or spine bone outcomes. Additional adjustment for gestational age partially attenuated associations between breech presentation and bone outcomes e.g. neonatal BA (−6.7 cm², 95%CI −14.2 cm² to 0.3 cm², P=0.083) and four year hip BA (−0.61 cm², 95%CI −1.17 cm² to −0.04 cm², P=0.035).

These results suggest that breech presentation is associated with lower neonatal whole body BMC, BA and BMD, and with lower hip BMC and BA at 4 years. These associations are in part explained by differences in gestational age. The associations with hip bone parameters at age 4 years correspond to the location of dysplasias found commonly in breech presentation.

Disclosure: The authors declared no competing interests.