title: Preterm Infant Growth Velocity Calculations: A Systematic Review.
abstract: BACKGROUND
  Clinicians assess the growth of preterm infants and compare growth velocity using a variety of methods.
  
  
  OBJECTIVE
  We determined the numerical methods used to describe weight, length, and head circumference growth velocity in preterm infants; these methods include grams/kilogram/day (g/kg/d), grams/day (g/d), centimeters/week (cm/week), and change inzscores.
  
  
  METHODS
  A search was conducted in April 2015 of the Medline database by using PubMed for studies that measured growth as a main outcome in preterm neonates between birth and hospital discharge and/or 40 weeks' postmenstrual age. English, French, German, and Spanish articles were included. The systematic review was conducted by using Preferred Reporting Items for Systematic Reviews and Meta-analyses methods.
  
  
  METHODS
  Of 1543 located studies, 373 (24%) calculated growth velocity.
  
  
  METHODS
  We conducted detailed extraction of the 151 studies that reported g/kg/d weight gain velocity.
  
  
  RESULTS
  A variety of methods were used. The most frequently used method to calculate weight gain velocity reported in the 1543 studies was g/kg/d (40%), followed by g/d (32%); 29% reported change inzscore relative to an intrauterine or growth chart. In the g/kg/d studies, 39% began g/kg/d calculations at birth/admission, 20% at the start of the study, 10% at full feedings, and 7% after birth weight regained. The kilogram denominator was not reported for 62%. Of the studies that did report the denominators, the majority used an average of the start and end weights as the denominator (36%) followed by exponential methods (23%); less frequently used denominators included birth weight (10%) and an early weight that was not birth weight (16%). Nineteen percent (67 of 355 studies) made conclusions regarding extrauterine growth restriction or postnatal growth failure. Temporal trends in head circumference growth and length gain changed from predominantly cm/wk to predominantlyzscores.
  
  
  CONCLUSIONS
  The lack of standardization of methods used to calculate preterm infant growth velocity makes comparisons between studies difficult and presents an obstacle to using research results to guide clinical practice.
authors.affiliation: Department of Community Health Sciences, Institute of Public Health, Alberta Children's Hospital Research Institute, and tfenton@ucalgary.ca.|Nutrition Services, Alberta Health Services, Calgary, Alberta, Canada.
authors.forename: Tanis R
authors.initials: TR
authors.lastname: Fenton
authors.affiliation: Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Hilton T
authors.initials: HT
authors.lastname: Chan
authors.affiliation: Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Aiswarya
authors.initials: A
authors.lastname: Madhu
authors.affiliation: UC Davis Medical Center, Sacramento, California.
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Griffin
authors.affiliation: Clínica del Country, Universidad el Bosque, Bogotá, Colombia.
authors.forename: Angela
authors.initials: A
authors.lastname: Hoyos
authors.affiliation: University of Iowa Children's Hospital, Iowa City, Iowa.
authors.forename: Ekhard E
authors.initials: EE
authors.lastname: Ziegler
authors.affiliation: Case Western Reserve University School of Medicine, Cleveland, Ohio.
authors.forename: Sharon
authors.initials: S
authors.lastname: Groh-Wargo
authors.affiliation: University of Iowa Children's Hospital, Iowa City, Iowa.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Carlson
authors.affiliation: CHU de Liege, CHR de la Citadelle, University of Liege, Liege, Belgium.
authors.forename: Thibault
authors.initials: T
authors.lastname: Senterre
authors.affiliation: Baylor College of Medicine, Houston, Texas; and.
authors.forename: Diane
authors.initials: D
authors.lastname: Anderson
authors.affiliation: Yale School of Medicine, New Haven, Connecticut.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Ehrenkranz
mesh_terms: D001827:Body Height; D002508:Cephalometry; D006801:Humans; D007223:Infant; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007234:Infant, Premature / Q000254:growth & development*; D008954:Models, Biological; D015430:Weight Gain