Maternal human milk feedings continue an offspring’s exposure to the programming stimuli of maternal metabolism during the postnatal period. While considerable research focuses on associations between in utero environments and offspring metabolic disease, few studies have been able to specifically measure how human milk composition modifies programming of children’s growth in conjunction with comprehensive measures of maternal glycaemia during pregnancy.

The Glycemia Range and Offspring Weight and adiposity in response To Human milk (GROWTH) Study is a longitudinal cohort enrolling women with a singleton pregnancy who (1) undergo serial testing of glycaemia during pregnancy and (2) are intending to provide their breast milk through direct breastfeeding or pumped milk as the primary nutrition for their infant. Enrolment started in October 2023 and is expected to be completed in December 2026. Key procedures include virtual lactation support visits, serial human milk sampling at three time points, maternal and infant blood sampling, serial maternal and child anthropometric measurements and diet assessment. After delivery, mother–child dyads are followed until children turn 2 years of age. The primary exposure variable is maternal glycaemia obtained from a fasting, 3 hour 100 g oral glucose tolerance test performed at 24–28 weeks of gestation, and the primary outcome measure is the composite of human milk linoleic and docosahexaenoic acid concentrations in milk samples collected at 1 month postpartum.

Lurie Children’s Hospital Institutional Review Board (IRB) provides central oversight of the GROWTH Study in conjunction with each participating centre’s IRB. The GROWTH Study data has the potential to inform perinatal health and future research in lactation and human milk science by providing comprehensive measures of human milk composition and early childhood growth and body composition parameters impacted by maternal metabolism in pregnancy.