title: Sexually dimorphic response to feeding mode in the growth of infants.
abstract: BACKGROUND
  The relation between infant feeding and growth has been extensively evaluated, but studies examining sex differences in the influence of infant milk feeding on growth are limited.
  
  
  OBJECTIVE
  We examined the interaction of infant feeding and sex in relation to infant growth and compared growth trajectories in breastfed and formula-fed boys and girls.
  
  
  METHODS
  In 932 infants in a Singapore mother-offspring cohort, feeding practices in the first 6 mo were classified into the breastfeeding group (BF), mixed feeding group (MF), and formula feeding group (FF). Infant weight and length were measured and converted to WHO standards for weight-for-age z scores (WAZs) and length-for-age z scores (LAZs). Differences in WAZ and LAZ from birth to 6 mo, 6 to 12 mo, and 12 to 24 mo of age were calculated. Three-way interactions were examined between feeding mode, sex, and age intervals for WAZ and LAZ changes, with adjustment for confounders.
  
  
  RESULTS
  The interaction between feeding mode, sex, and age intervals was significant for LAZ changes (P = 0.003) but not WAZ changes (P = 0.103) after adjustment for potential confounders. Compared with BF girls, BF boys showed similar LAZ gain (+0.28 compared with +0.39, P = 0.544) from 0 to 6 mo of age but greater LAZ gain from 6 to 12 mo of age (+0.39 compared with -0.10, P = 0.008). From 0 to 6 mo of age, FF boys and girls showed greater LAZ gains than their BF counterparts; from 6 to 12 mo of age, FF girls showed higher LAZ gain (+0.25 compared with -0.10, P = 0.031) than BF girls, which was not seen in boys.
  
  
  CONCLUSIONS
  During infancy, there is a sexually dimorphic growth response to the mode of infant milk feeding, raising questions about whether formula feeding ought to remain sex neutral. However, further investigations on sex-specific feeding and infant growth are warranted before a conclusive message can be drawn based on our current findings. This trial was registered at www.clinicaltrials.gov as NCT01174875.
authors.affiliation: Department of Paediatrics.
authors.forename: Tuck Seng
authors.initials: TS
authors.lastname: Cheng
authors.affiliation: KK Research Centre.
authors.forename: See Ling
authors.initials: SL
authors.lastname: Loy
authors.affiliation: Center for Quantitative Medicine, and Department for International Health, University of Tampere, Tampere, Finland;
authors.forename: Yin Bun
authors.initials: YB
authors.lastname: Cheung
authors.affiliation: KK Research Centre, Department of Reproductive Medicine, and Duke-NUS Medical School, Singapore;
authors.forename: Jerry Kok Yen
authors.initials: JK
authors.lastname: Chan
authors.affiliation: Department of Obstetrics and Gynaecology, and.
authors.forename: Wei Wei
authors.initials: WW
authors.lastname: Pang
authors.affiliation: MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, United Kingdom; NIHR Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom;
authors.forename: Keith M
authors.initials: KM
authors.lastname: Godfrey
authors.affiliation: Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research, Singapore; and Liggins Institute, University of Auckland, Auckland, New Zealand.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Gluckman
authors.affiliation: Department of Maternal Foetal Medicine, KK Women's and Children's Hospital, Singapore;
authors.forename: Kenneth
authors.initials: K
authors.lastname: Kwek
authors.affiliation: Saw Swee Hock School of Public Health, National University of Singapore, Singapore;
authors.forename: Seang Mei
authors.initials: SM
authors.lastname: Saw
authors.affiliation: Department of Obstetrics and Gynaecology, and.
authors.forename: Yap-Seng
authors.initials: YS
authors.lastname: Chong
authors.affiliation: Department of Paediatrics, Yong Loo Ling School of Medicine, and Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research, Singapore; and.
authors.forename: Yung Seng
authors.initials: YS
authors.lastname: Lee
authors.affiliation: Department of Paediatrics, Duke-NUS Medical School, Singapore;
authors.forename: Ngee
authors.initials: N
authors.lastname: Lek
authors.affiliation: Department of Paediatrics, Duke-NUS Medical School, Singapore; fabian.yap.k.p@singhealth.com.sg.
authors.forename: Fabian
authors.initials: F
authors.lastname: Yap
mesh_terms: D001827:Body Height; D001903:Bottle Feeding / Q000009:adverse effects; D001942:Breast Feeding / Q000009:adverse effects; D002657:Child Development; D015331:Cohort Studies; D005260:Female; D057238:Growth Charts; D006801:Humans; D041943:Infant Formula / Q000008:administration & dosage*; D007227:Infant Nutritional Physiological Phenomena; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D009035:Mothers; D012727:Sex Characteristics; D012846:Singapore; D015430:Weight Gain
keywords: breastfeeding; formula feeding; gender; growth; infant; interaction