Role of gestational age and intrauterine growth on bone mass in adolescents: findings from a Brazilian Birth Cohort Study.

Osteoporosis in adulthood often originates in early life, and some forms can be prevented through appropriate attention to bone health during the neonatal period and childhood, particularly in cases involving preterm infants or with intrauterine growth restriction.

Purpose: To test the association of gestational age and intrauterine growth with bone mass in adolescents.

Methods: With data from the 2004 Pelotas Birth Cohort, the outcomes density (aBMD) and content (BMC) were obtained by dual-energy X-ray absorptiometry, measured at 15 years. The exposures of interest were: prematurity (< 37 weeks of gestation), gestational age (≤ 36, 37-41, and ≥ 42 weeks) and intrauterine growth (small - SGA, appropriate - AGA or large for gestational age - LGA). Linear regression stratified by sex was run. Exclusive breastfeeding at 3 months was tested as an effect modifier.

Results: One thousand four hundred ninety-four participants were included. In full adjusted model, including adolescent's height, preterm females had lower aBMD femoral neck than the full-term (β - 0.04 g/cm²; 95% CI - 0.07; - 0.01; p = 0.012) and those born with ≥ 42 weeks of gestation (β - 0.07 g/cm²; 95% CI - 0.13; - 0.01; p = 0.026). Males born with ≤ 36 and 37-41 weeks of gestation presented less BMC femoral neck than those born with ≥ 42 weeks (β - 0.8 g; 95% CI - 1.4; - 0.2 and β - 0.8 g; 95% CI - 1.4; - 0.2, respectively). LGA females presented approximately 100 g more in the whole-body BMC (β 97.3 g; 95% CI 20.5; 174.1; p = 0.022) than AGA females. SGA females who received exclusive breastfeeding at 3 months presented higher BMD (lumbar spine and femoral neck) and BMC than those who did not receive exclusive breastfeeding.

Conclusion: Even the adolescence phase can be impaired due to premature birth and intrauterine growth restriction.