Introduction: Intrauterine weeks 3638 with rapid transplacental mineral transfer are crucial for skeletal development. Prematurity and low birthweight may therefore lead to a subnormal peak bone mass. We evaluated the influence of gestational age and low birthweight on bone mineral density (BMD) and content (BMC) in young adults born preterm with very low birthweight (VLBW) and small for gestational age (SGA) at term.
Description of methods/design: Altogether, 186 subjects (females=95) 2628 years of age were included. Of these, 52 were born preterm with VLBW (<1500 g), 56 born SGA at term (<10th percentile) and 75 controls born at term with normal birthweight (>10th percentile). Weight, height, previous fractures, smoking, physical activity, calcium and vitamin D intake were recorded. BMC and BMD at spine, femoral neck, hip and whole body and spine trabecular bone score (TBS) were measured by DXA. Serum bone markers were analyzed.
Results: The VLBW and SGA groups were significantly shorter compared to controls. The VLBW group was more physically inactive and reported higher calcium intake. Previous fractures, smoking and vitamin D were similar between the groups. The VLBW group exhibited significantly lower BMC and BMD at most sites measured, also controlled for known confounders. Femoral neck BMD was 6.7% lower in VLBW. BMD was apparently dependent on gestational age, as each additional week of gestation resulted in 0.037 units increase in femoral neck Z-score. The SGA group displayed lower BMC at spine and lower whole body Z-score. No differences were observed in TBS or bone markers, except for higher Dkk1 in the VLBW groups.
Conclusion: Adults born premature with VLBW and SGA at term displayed significantly shorter height, and lower BMC and BMD compared to controls. The lower peak bone mass may imply an increased fracture risk in the future.