title: Postnatal growth standards for preterm infants: the Preterm Postnatal Follow-up Study of the INTERGROWTH-21(st) Project.
abstract: BACKGROUND
  Charts of size at birth are used to assess the postnatal growth of preterm babies on the assumption that extrauterine growth should mimic that in the uterus.
  
  
  METHODS
  The INTERGROWTH-21(st) Project assessed fetal, newborn, and postnatal growth in eight geographically defined populations, in which maternal health care and nutritional needs were met. From these populations, the Fetal Growth Longitudinal Study selected low-risk women starting antenatal care before 14 weeks' gestation and monitored fetal growth by ultrasonography. All preterm births from this cohort were eligible for the Preterm Postnatal Follow-up Study, which included standardised anthropometric measurements, feeding practices based on breastfeeding, and data on morbidity, treatments, and development. To construct the preterm postnatal growth standards, we selected all live singletons born between 26 and before 37 weeks' gestation without congenital malformations, fetal growth restriction, or severe postnatal morbidity. We did analyses with second-degree fractional polynomial regression models in a multilevel framework accounting for repeated measures. Fetal and neonatal data were pooled from study sites and stratified by postmenstrual age. For neonates, boys and girls were assessed separately.
  
  
  RESULTS
  From 4607 women enrolled in the study, there were 224 preterm singleton births, of which 201 (90%) were enrolled in the Preterm Postnatal Follow-up Study. Variance component analysis showed that only 0·2% and 4·0% of the total variability in postnatal length and head circumference, respectively, could be attributed to between-site differences, justifying pooling the data from all study sites. Preterm growth patterns differed from those for babies in the INTERGROWTH-21(st) Newborn Size Standards. They overlapped with the WHO Child Growth Standards for term babies by 64 weeks' postmenstrual age.
  
  
  CONCLUSIONS
  Our data have yielded standards for postnatal growth in preterm infants. These standards should be used for the assessment of preterm infants until 64 weeks' postmenstrual age, after which the WHO Child Growth Standards are appropriate. Size-at-birth charts should not be used to measure postnatal growth of preterm infants.
  
  
  BACKGROUND
  Bill & Melinda Gates Foundation.
authors.affiliation: Nuffield Department of Obstetrics & Gynaecology and Oxford Maternal & Perinatal Health Institute, Green Templeton College, University of Oxford, Oxford, UK. Electronic address: jose.villar@obs-gyn.ox.ac.uk.
authors.forename: José
authors.initials: J
authors.lastname: Villar
authors.affiliation: Dipartimento di Scienze della Sanita Pubblica e Pediatriche, Struttura Complessa di Neonatologia Universitaria, Universiti degli Studi di Torino, Turin, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Giuliani
authors.affiliation: Center of Excellence in Women & Child Health, Aga Khan University, Karachi, Pakistan; Center for Global Child Health, Hospital for Sick Children, Toronto, Canada.
authors.forename: Zulfiqar A
authors.initials: ZA
authors.lastname: Bhutta
authors.affiliation: Dipartimento di Scienze della Sanita Pubblica e Pediatriche, Struttura Complessa di Neonatologia Universitaria, Universiti degli Studi di Torino, Turin, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Bertino
authors.affiliation: Nuffield Department of Obstetrics & Gynaecology and Oxford Maternal & Perinatal Health Institute, Green Templeton College, University of Oxford, Oxford, UK; Centre for Statistics in Medicine, Botnar Research Centre, University of Oxford, Oxford, UK.
authors.forename: Eric O
authors.initials: EO
authors.lastname: Ohuma
authors.affiliation: Nuffield Department of Obstetrics & Gynaecology and Oxford Maternal & Perinatal Health Institute, Green Templeton College, University of Oxford, Oxford, UK.
authors.forename: Leila Cheikh
authors.initials: LC
authors.lastname: Ismail
authors.affiliation: Programa de Pós-Graduação em Epidemiologia, Universidade Federal de Pelotas, Pelotas, RS, Brazil; Programa de Pós-Graduação em Saúde e Comportamento, Unversidade Católica de Pelotas, Pelotas, RS, Brazil.
authors.forename: Fernando C
authors.initials: FC
authors.lastname: Barros
authors.affiliation: Centre for Statistics in Medicine, Botnar Research Centre, University of Oxford, Oxford, UK.
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Altman
authors.affiliation: Programa de Pós-Graduação em Epidemiologia, Universidade Federal de Pelotas, Pelotas, RS, Brazil.
authors.forename: Cesar
authors.initials: C
authors.lastname: Victora
authors.affiliation: Department of Engineering Science, University of Oxford, Oxford, UK.
authors.forename: Julia A
authors.initials: JA
authors.lastname: Noble
authors.affiliation: Global Alliance to Prevent Prematurity and Stillbirth (GAPPS), Seattle Childrens' Hospital, Seattle, WA, USA.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Gravett
authors.affiliation: Nagpur INTERGROWTH-21(st) Research Centre, Ketkar Hospital, Nagpur, India.
authors.forename: Manorama
authors.initials: M
authors.lastname: Purwar
authors.affiliation: School of Public Health, Peking University, Beijing, China.
authors.forename: Ruyan
authors.initials: R
authors.lastname: Pang
authors.affiliation: Nuffield Department of Obstetrics & Gynaecology and Oxford Maternal & Perinatal Health Institute, Green Templeton College, University of Oxford, Oxford, UK.
authors.forename: Ann
authors.initials: A
authors.lastname: Lambert
authors.affiliation: Nuffield Department of Obstetrics & Gynaecology and Oxford Maternal & Perinatal Health Institute, Green Templeton College, University of Oxford, Oxford, UK.
authors.forename: Aris T
authors.initials: AT
authors.lastname: Papageorghiou
authors.affiliation: Faculty of Health Sciences, Aga Khan University, Nairobi, Kenya.
authors.forename: Roseline
authors.initials: R
authors.lastname: Ochieng
authors.affiliation: Department of Family & Community Health, Ministry of Health, Muscat, Sultanate of Oman.
authors.forename: Yasmin A
authors.initials: YA
authors.lastname: Jaffer
authors.affiliation: Nuffield Department of Obstetrics & Gynaecology and Oxford Maternal & Perinatal Health Institute, Green Templeton College, University of Oxford, Oxford, UK.
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Kennedy
mesh_terms: D000886:Anthropometry / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature / Q000254:growth & development*; D008297:Male; D011247:Pregnancy; D012015:Reference Standards; D012044:Regression Analysis