title: [Factors influencing the bone mineral density in preterm infants].
abstract: OBJECTIVE
  To study the bone mineral development and the factors influencing the development in preterm infants.
  
  
  METHODS
  Ninety preterm and 90 term infants followed up by the child health care service were randomly enrolled. Tibia quantitative ultrasound measurements were used to evaluate bone mineral density described as supersonic speed of sound (SOS) and Z scores at 6 months old (corrected gestational age for preterm infants). The factors influencing bone mineral development were investigated by questionnaire.
  
  
  RESULTS
  The SOS values and Z scores in term infants were significantly higher than those in preterm infants at 6 months old. In the preterm group, the SOS values and Z scores were significantly different in infants with different birth weights or gestational ages (P<0.05). The SOS values in preterm infants with different weaning time were significantly different. The Z scores in female preterm infants were significantly higher than that in males (P<0.05). Multiple regression analysis indicated that weaning time and daily time of outdoor activities were independent factors influencing SOS values in preterm infants.
  
  
  CONCLUSIONS
  It is helpful to promote bone mineral development by an appropriate weaning time or increasing the time of outdoor activities in preterm infants.
authors.affiliation: Department of Pediatrics, West China Second Hospital of Sichuan University, Chengdu, China.
authors.forename: Wen-Xu
authors.initials: WX
authors.lastname: Yang
authors.forename: Hui-Ming
authors.initials: HM
authors.lastname: Yang
mesh_terms: D015519:Bone Density; D001942:Breast Feeding; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology*; D008297:Male; D012044:Regression Analysis; D012727:Sex Characteristics