Interim analysis (n=40 24-hr sessions) yielded biologically implausible data. We do not deem this novel, at-home, participant-led method prudent. Study will continue with only secondary objectives; primary objective (RCT) terminated.

Nova Scotia has among the lowest breastfeeding rates in Canada, with less than one quarter of infants receiving Health Canada's recommended 6 months of exclusive breastfeeding. Compared with feeding formula, breastfeeding has been linked with a number of health advantages, including fewer infections, higher IQ, and a lowered risk of obesity later in life.

How infants consume human milk is changing. Pumping milk has grown in popularity in recent years because some mothers may feel stigmatized breastfeeding, especially in public, but also because it allows other caregivers to help with feeding. Although pumped human milk is considered equal to breastfeeding, there is very little research in this area, especially around responsive feeding and later health outcomes. Since pumped milk is fed from a bottle, the health benefits may be lost (for instance, this may impact a baby's ability to understand if s/he is hungry or full).

The primary aim of this study is to determine if the volume of human milk an infant consumes differs if they consume milk from a bottle versus the breast. The investigators will conduct a cross-over trial in which 62 mother-infant pairs will be randomized to feed at the breast or from a bottle for 24 hours, have a 24 hour wash-out period, and then 'cross-over' to another 24 hour session with the opposite 'treatment.' The volume of milk consumed at each feed within the 24 hour window (via indirect weighing, or weighing the baby before and after eating) will be recorded to determine if there are differences in milk consumption. Mother-infant pairs will complete this 3-day study three times, at 6 weeks, 4 months, and 6 months.

Information from this study will help to better understand current infant feeding practices in Nova Scotia, and the potential role this plays in future health outcomes. Evidence from this study may help to identify means of improving feeding practices and promoting human milk as the main food for Nova Scotian infants, setting them on a path for the best start in life.

See attached full protocol document for full details.

Inclusion criteria: Mother-infant dyads are eligible to participate if:

• mother is aged 19 years or older,
• dyads currently live in the Halifax Regional Municipality in Nova Scotia,
• mother has no chronic diseases,
• the baby is a healthy singleton baby who is younger than 6 weeks of age, and is fed mother's milk directly from the breast and from a bottle,
• mother plans to exclusively feed their baby mother's own milk up to 6 months,
• mother has/had an older child whom they successfully fed mother's own milk for a minimum of 6 months,
• mother is willing to participate in three 3-day study sessions and monthly measurement sessions, and
• mother provides informed consent for herself and her infant to participate.

Exclusion criteria: Mother-infant dyads are ineligible to participate if:

• the baby was born preterm (earlier than 37 weeks gestation),
• the baby was born outside the healthy weight range of 2,500 - 4,000 g (5lb 8oz to 8lb 13oz),
• the baby has a developmental delay diagnosed before the time of enrolment,
• the baby is currently receiving any medical treatment except for vitamin D supplementation (no more than 400 IU/day),
• the mother sought prescription medical treatment for lactation (e.g. domperidone, antibiotics, prescription nipple ointment), or
• the mother plans to move in the 6 months after starting the study.