Biological signaling and communication between mothers and infants during breastfeeding may shape infant behavior and feeding. This signaling is complex and little explored in humans, although it is potentially relevant for initiatives to improve breastfeeding rates. The aim of this study was to investigate physiological and psychological aspects of mother-infant signaling during breastfeeding experimentally, testing the effects of a relaxation intervention on maternal psychological state, breast milk intake, milk cortisol levels, and infant behavior and growth. Primiparous breastfeeding mothers and full-term infants were randomly assigned to receive relaxation therapy [intervention relaxation group; n = 33 (RG)] or to the control group [n = 31 (CG); no relaxation therapy] at 2 wk postpartum. Both groups received standard breastfeeding support. Home visits were conducted at 2 (HV1), 6 (HV2), 12 (HV3) and 14 (HV4) wk to measure maternal stress and anxiety, breast milk intake and milk cortisol, and infant behavior and growth. RG mothers had lower stress scores postintervention than the CG (HV3 ∆ = -3.13; 95% CI: -5.9, -0.3) and lower hindmilk cortisol at HV1 (∆ = -44.5%; 95% CI: -76.1%, -12.9%) but not at HV2. RG infants had longer sleep duration (∆ = 82 min/d; 95% CI: 16, 149 min/d) at HV2 and higher gains in weight and body mass index standardized deviation score than the CG infants (∆ = 0.76; 95% CI: 0.3, 1.22; and ∆ = 0.59; 95% CI: 0.09, 1.1, respectively). RG infants had a mean milk intake at HV3 that was 227 g/d higher than that of the CG infants (P = 0.031) after controlling for gender and milk intake at HV1. The trial shows the effectiveness of a simple relaxation intervention for improving maternal and infant outcomes and identifies some potential signaling mechanisms for investigation in future and larger studies, especially in settings where mothers are more stressed, such as those with preterm or low birth weight infants. This trial was registered at clinicaltrials.gov as NCT01971216.

Human milk is a highly complex liquid food tailor-made to match an infant’s needs. Beyond documented positive effects of breastfeeding on infant and maternal health, there is increasing evidence that milk constituents also impact child neurodevelopment. Non-nutrient milk bioactives would contribute to the (long-term) development of child cognition and behavior, a process termed ‘Lactocrine Programming’. In this review we discuss the current state of the field on human milk composition and its links with child cognitive and behavioral development. To promote state-of-the-art methodologies and designs that facilitate data pooling and meta-analytic endeavors, we present detailed recommendations and best practices for future studies. Finally, we determine important scientific gaps that need to be filled to advance the field, and discuss innovative directions for future research. Unveiling the mechanisms underlying the links between human milk and child cognition and behavior will deepen our understanding of the broad functions of this complex liquid food, as well as provide necessary information for designing future interventions.

Background: The exclusive breastfeeding rate in Malaysia is still not satisfactory. Previous studies have shown that breastfeeding self-efficacy is one of the determinants of exclusive breastfeeding, and it can be improved using social cognitive theory. WhatsApp, which is widely used among Malaysians, could be leveraged as a platform to deliver health education interventions. Objective: This study aimed to develop, implement, and evaluate the effect of using a face-to-face and WhatsApp-based health education intervention based on social cognitive theory, namely the Self-Efficacy in Breastfeeding (SeBF) module, on mothers' self-efficacy, knowledge, and attitudes in a district in Selangor state. Methods: This study was a 2-arm, parallel, single-blind, cluster randomized controlled field trial with an intervention and a control group involving primigravida or multigravida mothers who reside in a district in Selangor state and did not exclusively breastfeed during their previous pregnancy. All 12 maternity and pediatric clinics in this district were randomly divided into 6 intervention and 6 control groups. A total of 172 pregnant mothers were randomly assigned to the intervention group (n=86) or the control group (n=86). The control group received usual routine care. The primary outcome was breastfeeding self-efficacy, while secondary outcomes were knowledge and attitude toward breastfeeding. Each subject was assessed at 4 time points: at baseline, immediately after the intervention, 4 weeks post partum, and 8 weeks post partum. Generalized mixed model analysis was applied to measure the effect of health education on breastfeeding self-efficacy, knowledge, and attitude after the intervention. Results: The response rate was 81% (139/172), with the dropout rate being 7% (6/86) in the intervention group and 31% (27/86) in the control group. In the intent-to-treat analysis, the intervention group showed a significant increase in the mean total breastfeeding self-efficacy score 8 weeks after delivery compared with the control group (F21,601=111.73, P<.001). In addition, the mean total score for breastfeeding knowledge increased significantly in the intervention group after the intervention compared to the control group (F21,601=8.33, P<.001). However, no significant difference was found in the mean total score for breastfeeding attitude after the intervention (F21,602=5.50, P=.47). Conclusions: Face-to-face and WhatsApp-based participation in the SeBF program, designed on the basis of social cognitive theory, contributed to improved self-efficacy and knowledge about breastfeeding. Further studies need to be conducted with a longer duration (until 6 months post partum) to evaluate its effectiveness in increasing exclusive breastfeeding. Furthermore, new strategies in health education need to be developed to improve breastfeeding attitudes. Trial Registration: Thaiclinicaltrials.org TCTR20200213004; https://www.thaiclinicaltrials.org/show/TCTR20200213004

Background: Promoting breastfeeding is an important public health intervention, with benefits for infants and mothers. Even modest increases in prevalence and duration may yield considerable economic savings. However, despite many initiatives, compliance with recommendations is poor in most settings – particularly for exclusive breastfeeding. Mothers commonly consult health professionals for infant feeding and behavioural problems. Main body: We argue that broader consideration of lactation, incorporating evolutionary, comparative and anthropological aspects, could provide new insights into breastfeeding practices and problems, enhance research and ultimately help to develop novel approaches to improve initiation and maintenance. Our current focus on breastfeeding as a strategy to improve health outcomes must engage with the evolution of lactation as a flexible trait under selective pressure to maximise reproductive fitness. Poor understanding of the dynamic nature of breastfeeding may partly explain why some women are unwilling or unable to follow recommendations. Conclusions: We identify three key implications for health professionals, researchers and policymakers. Firstly, breastfeeding is an adaptive process during which, as in other mammals, variability allows adaptation to ecological circumstances and reflects mothers’ phenotypic variability. Since these factors vary within and between humans, the likelihood that a ‘one size fits all’ approach will be appropriate for all mother-infant dyads is counterintuitive; flexibility is expected. From an anthropological perspective, lactation is a period of tension between mother and offspring due to genetic ‘conflicts of interest’. This may underlie common breastfeeding ‘problems’ including perceived milk insufficiency and problematic infant crying. Understanding this – and adopting a more flexible, individualised approach – may allow a more creative approach to solving these problems. Incorporating evolutionary concepts may enhance research investigating mother–infant signalling during breastfeeding; where possible, studies should be experimental to allow identification of causal effects and mechanisms. Finally, the importance of learned behaviour, social and cultural aspects of primate (especially human) lactation may partly explain why, in cultures where breastfeeding has lost cultural primacy, promotion starting in pregnancy may be ineffective. In such settings, educating children and young adults may be important to raise awareness and provide learning opportunities that may be essential in our species, as in other primates.

Maternal psychological state is recognised to influence lactation success, largely by affecting milk ejection. Thus, increased psychological distress can disrupt milk flow and in the long‐term, affect milk synthesis. Conversely, it is possible that milk ejection could be improved by using relaxation therapy during breastfeeding. We performed a systematic review to evaluate the effectiveness of interventions using relaxation therapy to improve breastfeeding outcomes and to assess the consequent impact(s) on infant growth and behaviour. A literature search was performed using the PRISMA guidelines where we included intervention studies (including nonrandomised controlled studies) using relaxation therapy in breastfeeding mothers during the post‐natal period. Out of 147 identified records at the initial search, 5 studies were eligible, of which 3 were randomised controlled trials and 2 were nonrandomised or quasi‐experimental studies. These studies were conducted in Europe, America, and India and included 311 mother–infant pairs, of which 64 infants were full‐term and 247 were premature infants. Relaxation therapy was shown to increase milk yield in mothers of preterm infants in 2 randomised trials, however, the milk sampling protocol for these studies could be questioned. None of the studies investigated the consequent effects on infant outcomes. Overall, limited evidence was found on the effectiveness of relaxation therapy on breast milk composition and infant outcomes. Experimental studies with better standardisation of protocol and robust methodological design are needed to investigate the effectiveness of relaxation therapy on both breastfeeding and infant growth and behavioural outcomes.