Table 3 Common methodological flaws of included studies (n = 20)

• Research question or study outcomes related to aBME not well-defined

• Incomplete description of study procedures preventing reproducibility (target population, inclusion/exclusion criteria, exposures/interventions, outcomes)

• Limited description of the aBME protocol and supports provided to study participants

• Limited information on the collection of colostrum from aBME, its use postpartum, and impact on the study outcomes

• Inadequate or incomplete measures of lactational and breastfeeding outcomes

• Limited information on participant retention and loss-to-follow-up, and comparative data between the final study sample and non-respondents/those lost during the course of the study

• Lack of comprehensive baseline data on study participants

• Limited collection or presentation of data on patterns of exclusive and mixed breastfeeding, pumping and infant formula supplementation, and little information on the reasons for infant formula supplementation (in-hospital or after discharge)

• For randomized trials, limited description of randomization, allocation and blinding procedures

• For quantitative studies, lack of pre-sample size calculations or power considerations

• For quantitative studies, inappropriate matching of comparisons groups, or insufficient description of the matching criteria

• For quantitative studies, not accounting for, or reporting on, participant compliance to the study intervention

• For qualitative studies, limited information on the validity of the data collection tools, theoretical frameworks applied to guide study design or data analysis

• For mixed methods studies, rationale for using a mixed-methods design was infrequently provided and there was limited integration of qualitative and quantitative findings

• Not accounting for confounding variables or mediating factors (e.g. parity, obesity, breastfeeding history in previous pregnancies, socioeconomic status and breastfeeding supports received)