Trajectories of length, weight, and bone mineral density among preterm infants during the first 12 months of corrected age in China

Background: Limited evidence has been provided on the trajectories of length, weight, and bone mineral density (BMD) among preterm infants in early life in Asian countries. Methods: We conducted a longitudinal study, which included 652 late preterm (gestational age: 34-36.9 weeks), 486 moderate preterm (32-33.9), 291 very preterm (28-31.9), 149 extremely preterm infants (<= 28.9) and 1434 full-term peers (>= 37) during the first 12 months of corrected age in Wuhan, China. Weight and length were measured at birth, once randomly before term, and every month thereafter. BMD was examined at 3, 6, 9 and 12 months using dual-energy X-ray absorptiometry. Results: From birth to 12 months of corrected age, growth peaks in length and weight were observed at 1-3 months among preterm infants. No catch-up growth in length, weight, and BMD was observed among preterm infants. However, accelerated growth in length, weight, and BMD was found. Among extremely preterm infants, relative to full-term infants, length was -6.77 cm (95 % CI: -7.14, -6.40; P for trend < 0.001) lower during the first 12 months; weight was -1.23 kg (-1.33, -1.13; P for trend < 0.001) lower; and BMD was -0.070 g/cm(2)(-0.087, -0.053; P for trend < 0.001) lower; however, average growth rates of these measures were higher (Ps < 0.05). Small gestational age and low birth weight were independently associated with lower length, weight, and BMD. Conclusion: Growth peaks in length and weight among preterm infants were observed at 1-3 months. No catch-up growth in length, weight, and BMD was observed, however, there was accelerated growth in length, weight, and BMD.