Fetal and infant growth predict hip geometry at 6 y old: findings from the Southampton Women's Survey

BACKGROUND: We investigated relationships between early growth and proximal femoral geometry at age 6 y in a prospective population-based cohort, the Southampton Women's Survey. METHODS: In 493 mother-offspring pairs, we assessed linear size using high-resolution ultrasound at 11, 19, and 34 wk gestation (femur length) and at birth and 1, 2, 3,4, and 6 y (crown-heel length/height). SD scores were created and conditional regression modeling generated mutually independent growth variables. Children underwent hip dual-energy X-ray absorptiometry (DXA) at 6 y; hip structure analysis software yielded measures of geometry and strength. RESULTS: There were strong associations between early linear growth and femoral neck section modulus (Z) at 6 y, with the strongest relationships observed for femur growth from 19 to 34 wk gestation (beta = 0.26 cm(3)/SD, P < 0.0001), and for height growth from birth to 1 y (beta = 0.25 cm(3)/SD, P < 0.0001) and 1 to 2 y (beta = 0.33 cm(3)/SD, P < 0.0001), with progressively weaker relationships over years 3 (beta = 0.23 cm(3)/SD, P = 0.0002) and 4 (beta = 0.10 cm(3)/SD, P = 0.18). CONCLUSION: These results demonstrate that growth before age 3 y predicts proximal femoral geometry at 6 y old. These data suggest critical periods in which there is capacity for long-term influence on the later skeletal growth trajectory.