nutrients Article Extensive Study of Breast Milk and Infant Growth: Protocol of the Cambridge Baby Growth and Breastfeeding Study (CBGS-BF) Laurentya Olga 1 , Clive J. Petry 1 , Janna A. van Diepen 2 , Philippa M. Prentice 1 , Ieuan A. Hughes 1 , Jacques Vervoort 3,† , Jos Boekhorst 4 , Maciej Chichlowski 5 , Gabriele Gross 2 , David B. Dunger 1,6,† and Ken K. Ong 1,6,7, *   Citation: Olga, L.; Petry, C.J.; van Diepen, J.A.; Prentice, P.M.; Hughes, I.A.; Vervoort, J.; Boekhorst, J.; Chichlowski, M.; Gross, G.; Dunger, D.B.; et al. Extensive Study of Breast Milk and Infant Growth: Protocol of the Cambridge Baby Growth and Breastfeeding Study (CBGS-BF). Nutrients 2021, 13, 2879. https:// doi.org/10.3390/nu13082879 Academic Editor: Johannes B. van Goudoever Received: 23 July 2021 Accepted: 19 August 2021 Published: 21 August 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Paediatrics, University of Cambridge, Cambridge CB2 0QQ, UK; lo290@medschl.cam.ac.uk (L.O.); cjp1002@medschl.cam.ac.uk (C.J.P.); philippaprentice@doctors.org.uk (P.M.P.); iah1000@medschl.cam.ac.uk (I.A.H.); dbd25@cam.ac.uk(D.B.D.) 2 Department of Internal Medicine and Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6545 CJ Nijmegen, The Netherlands; Janna.vanDiepen@rb.com (J.A.v.D.); Gabriele.Gross@rb.com (G.G.) 3 Laboratory of Biochemistry, Wageningen University, 6708 PB Wageningen, The Netherlands; jacques.vervoort@wur.nl 4 NIZO Food Research BV, 6718 ZB Ede, The Netherlands; Jos.Boekhorst@nizo.com 5 Department of Medical Affairs, Mead Johnson Nutrition, Evansville, IN 47721, USA; Maciej.Chichlowski@rb.com 6 Wellcome-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK 7 MRC Epidemiology Unit, University of Cambridge, Cambridge CB2 0SL, UK * Correspondence: Ken.Ong@mrc-epid.cam.ac.uk † Deceased. Abstract: Growth and nutrition during early life have been strongly linked to future health and metabolic risks. The Cambridge Baby Growth Study (CBGS), a longitudinal birth cohort of 2229 mother– infant pairs, was set up in 2001 to investigate early life determinant factors of infant growth and body composition in the UK setting. To carry out extensive profiling of breastmilk intakes and composition in relation to infancy growth, the Cambridge Baby Growth and Breastfeeding Study (CBGS-BF) was established upon the original CBGS. The strict inclusion criteria were applied, focusing on a normal birth weight vaginally delivered infant cohort born of healthy and non-obese mothers. Crucially, only infants who were exclusively breastfed for the first 6 weeks of life were retained in the analysed study sample. At each visit from birth, 2 weeks, 6 weeks, and then at 3, 6, 12, 24, and 36 months, longitudinal anthropometric measurements and blood spot collections were conducted. Infant body composition was assessed using air displacement plethysmography (ADP) at 6 weeks and 3 months of age. Breast milk was collected for macronutrients and human milk oligosaccharides (HMO) measurements. Breast milk intake volume was also estimated, as well as sterile breastmilk and infant stool collection for microbiome study. Keywords: infant growth; breast milk; early life; cohort profile; infant nutrition; breast milk nutrients; human milk oligosaccharides; breastfeeding; childhood obesity; prevention 1. Introduction The original Cambridge Baby Growth Study (CBGS) was set up in 2001, historically to investigate the effect of environmental factors on male reproductive development but then the entire birth cohort (males and females) were included to examine the ante- and postnatal determinants of infant growth and body composition, including genetic and environmental factors [1]. The recruitment took place until 2009 among pregnant mothers from a single maternity hospital in Cambridge. The study visits were conducted twice during pregnancy and four times postnatally at 3, 12, 18, and 24 months. The original CBGS Nutrients 2021, 13, 2879. https://doi.org/10.3390/nu13082879 https://www.mdpi.com/journal/nutrients