Unsolved Mysteries of the Human Mammary Gland: Defining and Redefining the Critical Questions from the Lactation Consultant's Perspective

Epigenetic impact of hypothyroidism on the functional differentiation of the mammary gland in rats

Mammary gland (MG) lactogenic differentiation involves epigenetic mechanisms. We have previously shown that hypothyroidism (HypoT) alters the MG transcriptome in lactation. However, the role of thyroid hormones (T3 and T4 a. k.a. THs) in epigenetic differentiation of MG is still unknown. We used a model of post-lactating HypoT rats to study in MG: a) Methylation and expression level of Gata3, Elf5, Stat6, Stat5a, Stat5b; b) Expression of Lalba, IL-4Rα and Ncoa1 mRNA; c) Histone H3 acetylation and d) Estrogen and progesterone concentration in serum. HypoT increases the estrogen serum level, decreases the progesterone level, promotes methylation of Stat5a, Stat5b and Stat6, decreasing their mRNA level and of its target genes (Lalba and IL-4Rα) and increases the Ncoa1 mRNA expression and histone H3 acetylation level. Our results proved that HypoT alters the post-lactation MG epigenome and could compromise mammary functional differentiation.

Mother's Emotional Experiences of Breastfeeding with Primary Low Milk Supply in the First Four Months Postpartum: An Interpretative Phenomenological Analysis

Background: Primary low milk supply (PLMS) prevents mothers from producing sufficient milk to breastfeed exclusively. However, limited evidence exists regarding women's experiences of breastfeeding with PLMS. Objective: This article aims to investigate the emotional experiences of mothers breastfeeding with PLMS in the first 3 months postpartum. Materials and Methods: The study was conducted in Ireland and used a phenomenological methodology to investigate the lived experiences of breastfeeding mothers with PLMS. Nine first-time breastfeeding mothers with PLMS participated, and data collection took the form of unstructured interviews. Data analysis was completed using Interpretative Phenomenological Analysis. Results: Being in the Whirlwind is one of four superordinate themes identified in this study. This theme relates to participants' internalized experiences of breastfeeding with PLMS in the first 3 months postpartum. During this time, participants struggled to come to terms with having PLMS and became caught up in all-consuming efforts to increase their milk supply. They experienced guilt, sadness, confusion, anger, and anxiety, with many describing the early months postpartum as traumatic. Participants revealed how triple-feeding (a regime of breastfeeding, pumping, and supplementing) negatively affected their mental health and reported that supplementing with infant formula was emotionally upsetting. Conclusions: Our findings reveal that the combination of PLMS and triple feeding can negatively impact a mothers' mental health. A greater understanding among health care professionals of the emotional impact of having PLMS and triple-feeding could enhance the provision of sensitive and person-centered support for those with PLMS. Antenatal breastfeeding education should acknowledge that PLMS is a challenge for a small cohort of women and place greater emphasis on the emotional aspects of breastfeeding challenges.

"I didn't want to let go of the dream": Exploring women's personal stories of how their low milk supply was discovered

PROBLEM

Low milk supply is the most common reason women give for stopping breastfeeding early and yet there is a lack of understanding about these women's experiences.

BACKGROUND

Most women plan to breastfeed but many experience challenges such as low milk production, leading them to seek help and support.

AIM

To explore women's personal stories of how their low supply was discovered.

METHODS

Inductive template analysis was used to analyse free-text online survey responses of women from the United States of America, Australia and the United Kingdom.

FINDINGS

384 women responded to the open-ended survey item between October 2021 and January 2022. We identified three themes: (i) Events and observations: From 'risk factors' to 'failure of breast changes' to 'my baby was so unhappy', (ii) Seeking support and taking action: 'I tried everything' and (iii) A rollercoaster of emotion: 'I didn't want to let go of the dream'.

DISCUSSION

Our findings emphasise women's need to feel heard and understood and their quest to find answers. The rollercoaster of emotions they experienced largely stemmed from a gap between the expectations and reality of breastfeeding. Some participants described accepting a different feeding journey.

CONCLUSION

Findings underscore the need for quality and accessible psychosocial support for women experiencing low milk supply, in addition to the provision of evidence-based advice.

Causes of Low Milk Supply: The Roles of Estrogens, Progesterone, and Related External Factors

Low milk supply (LMS) poses a significant challenge to exclusive and continued breastfeeding, affecting ∼10% to 15% of mothers. Milk production is intricately regulated by both endocrine and autocrine control mechanisms, with estrogens and progesterone playing pivotal roles in this process. In addition to endogenously produced hormones, external substances capable of interfering with normal hormonal actions, including phytoestrogens, mycoestrogens, synthetic estrogens, and hormonal contraceptives, can influence milk production. The effects of these extrinsic hormones on milk production may vary based on maternal body mass index. This comprehensive review examines the multifaceted causes of LMS, focusing on the involvement of estrogens, progesterone, and related external factors in milk production. Furthermore, it investigates the interplay between hormonal factors and obesity, aiming to elucidate the endocrine mechanisms underlying obesity-associated LMS. Insights from this review provide valuable perspectives for developing interventions to improve milk production and address the challenges associated with LMS.

Kindlin-2 in myoepithelium controls luminal progenitor commitment to alveoli in mouse mammary gland

Myoepithelium plays an important role in mammary gland development, but less is known about the molecular mechanism underlying how myoepithelium controls acinus differentiation during gestation. Herein, we found that loss of Kindlin-2 in myoepithelial cells impaired mammary morphogenesis, alveologenesis, and lactation. Using five genetically modified mouse lines combined with single-cell RNA sequencing, we found a Kindlin-2-Stat3-Dll1 signaling cascade in myoepithelial cells that inactivates Notch signaling in luminal cells and consequently drives luminal progenitor commitment to alveolar cells identity. Single-cell profiling revealed that Kindlin-2 loss significantly reduces the proportion of matured alveolar cells. Mechanistically, Kindlin-2 depletion in myoepithelial cells promotes Stat3 activation and upregulates Dll1, which activates the Notch pathway in luminal cells and inhibits luminal progenitor differentiation and maturation during gestation. Inhibition of Notch1 with tangeretin allowed luminal progenitors to regain commitment ability in the pregnant mice with Kindlin-2 depletion in myoepithelium. Taken together, we demonstrated that Kindlin-2 is essential to myoepithelium-controlled luminal progenitors to alveoli transition during gestation.

Parental factors that impact the ecology of human mammary development, milk secretion, and milk composition-a report from "Breastmilk Ecology: Genesis of Infant Nutrition (BEGIN)" Working Group 1

The goal of Working Group 1 in the Breastmilk Ecology: Genesis of Infant Nutrition (BEGIN) Project was to outline factors influencing biological processes governing human milk secretion and to evaluate our current knowledge of these processes. Many factors regulate mammary gland development in utero, during puberty, in pregnancy, through secretory activation, and at weaning. These factors include breast anatomy, breast vasculature, diet, and the lactating parent's hormonal milieu including estrogen, progesterone, placental lactogen, cortisol, prolactin, and growth hormone. We examine the effects of time of day and postpartum interval on milk secretion, along with the role and mechanisms of lactating parent-infant interactions on milk secretion and bonding, with particular attention to the actions of oxytocin on the mammary gland and the pleasure systems in the brain. We then consider the potential effects of clinical conditions including infection, pre-eclampsia, preterm birth, cardiovascular health, inflammatory states, mastitis, and particularly, gestational diabetes and obesity. Although we know a great deal about the transporter systems by which zinc and calcium pass from the blood stream into milk, the interactions and cellular localization of transporters that carry substrates such as glucose, amino acids, copper, and the many other trace metals present in human milk across plasma and intracellular membranes require more research. We pose the question of how cultured mammary alveolar cells and animal models can help answer lingering questions about the mechanisms and regulation of human milk secretion. We raise questions about the role of the lactating parent and the infant microbiome and the immune system during breast development, secretion of immune molecules into milk, and protection of the breast from pathogens. Finally, we consider the effect of medications, recreational and illicit drugs, pesticides, and endocrine-disrupting chemicals on milk secretion and composition, emphasizing that this area needs much more research attention.

Long-term impact of hypothyroidism during gestation and lactation on the mammary gland

The functional differentiation of the mammary gland (MG) is fundamental for the prevention of mammary pathologies. This process occurs throughout pregnancy and lactation, making these stages key events for the study of pathologies associated with development and differentiation. Many studies have investigated the link between mammary pathologies and thyroid diseases, but most have ignored the role of thyroid hormone (TH) in the functional differentiation of the MG. In this work, we show the long-term impact of hypothyroidism in an animal model whose lactogenic differentiation occurred at low TH levels. We evaluated the ability of the MG to respond to hormonal control and regulate cell cycle progression. We found that a deficit in TH throughout pregnancy and lactation induces a long-term decrease in Rb phosphorylation, increases p53, p21, Cyclin D1 and Ki67 expression, reduces progesterone receptor expression, and induces nonmalignant lesions in mammary tissue. This paper shows the importance of TH level control during mammary differentiation and its long-term impact on mammary function.

Fatty Acid Transfer from Blood to Milk Is Disrupted in Mothers with Low Milk Production, Obesity, and Inflammation

BACKGROUND

Obesity is associated with chronic inflammation and is a risk factor for insufficient milk production. Inflammation-mediated suppression of LPL could inhibit mammary uptake of long-chain fatty acids (LCFAs; >16 carbons).

OBJECTIVES

In an ancillary case-control analysis, we investigated whether women with low milk production despite regular breast emptying have elevated inflammation and disrupted transfer of LCFAs from plasma into milk.

METHODS

Data and specimens from a low milk supply study and an exclusively breastfeeding control group were analyzed, with milk production measured by 24-h test-weighing at 2-10 wk postpartum. Low milk supply groups were defined as very low (VL; <300 mL/d; n = 23) or moderate (MOD; ≥300 mL/d; n = 20) milk production, and compared with controls (≥699 mL/d; n = 18). Serum and milk fatty acids (weight% of total) were measured by GC, serum and milk TNF-α by ELISA, and serum high-sensitivity C-reactive protein (hsCRP) by clinical analyzer. Group differences were assessed by linear regression models, chi-square exact tests, and Kruskal-Wallis nonparametric tests.

RESULTS

VL cases, as compared with MOD cases and controls, had higher prevalence of elevated serum hsCRP (>5 mg/L; 57%, 15%, and 22%, respectively; P = 0.004), detectable milk TNF-α (67%, 32%, and 33%, respectively; P = 0.04), and obesity (78%, 40%, and 22%, respectively; P = 0.003). VL cases had lower mean ± SD LCFAs in milk (60% ± 3%) than MOD cases (65% ± 4%) and controls (66% ± 5%) (P < 0.001). Milk and serum LCFAs were strongly correlated in controls (r = 0.82, P < 0.001), but not in the MOD (r = 0.25, P = 0.30) or VL (r = 0.20, P = 0.41) groups (Pint < 0.001).

CONCLUSIONS

Mothers with very low milk production have significantly higher obesity and inflammatory biomarkers, lower LCFAs in milk, and disrupted association between plasma and milk LCFAs. These data support the hypothesis that inflammation disrupts normal mammary gland fatty acid uptake. Further research should address impacts of inflammation and obesity on mammary fatty acid uptake for milk production.

Obesity-derived alterations in the lactating mammary gland: Focus on prolactin

Obesity is a modern pandemic with negative consequences in women's reproductive health. Women with overweight and obesity can develop mammary gland alterations that unable exclusive breastfeeding. Obesity associates with a disturbed lactating mammary gland endocrine environment including a decreased action of the hormone prolactin (PRL), the master regulator of lactation. The PRL receptor and the action of PRL are reduced in the mammary gland of lactating rodents fed an obesogenic diet and are contributing factors to impaired lactation in obesity. Also, treatment with PRL improves milk yield in women with lactation insufficiency. This review focuses on the impact of diet-induced obesity in the lactating mammary gland and how obesity impairs the lactogenic action of PRL. Although obesity alters lactation performance in humans and rodents, the responsible mechanisms have been mainly addressed in rodents.

Oxylipins as Potential Regulators of Inflammatory Conditions of Human Lactation

Chronic low-grade inflammation can be associated with obesity or subclinical mastitis (SCM), which is associated with poor infant growth in low- to middle-income country settings. It is unknown what physiological mechanisms are involved in low milk supply, but our research group has shown that mothers with low milk supply have higher inflammatory markers. Studies investigating oxylipin signaling have the potential to help explain mechanisms that mediate the impacts of inflammation on milk production. Animal studies have reported various elevated oxylipins during postpartum inflammation, mastitis, and mammary involution in ruminant models. Several investigations have quantified oxylipins in human milk, but very few studies have reported circulating oxylipin concentrations during lactation. In addition, there are technical considerations that must be addressed when reporting oxylipin concentrations in human milk. First, the majority of milk oxylipins are esterified in the triglyceride pool, which is not routinely measured. Second, total milk fat should be considered as a covariate when using milk oxylipins to predict outcomes. Finally, storage and handling conditions of milk samples must be carefully controlled to ensure accurate milk oxylipin quantitation, which may be affected by highly active lipases in human milk.

Best practices to quantify the impact of reproductive toxicants on development, function, and diseases of the rodent mammary gland

Work from numerous fields of study suggests that exposures to hormonally active chemicals during sensitive windows of development can alter mammary gland development, function, and disease risk. Stronger links between many environmental pollutants and disruptions to breast health continue to be documented in human populations, and there remain concerns that the methods utilized to identify, characterize, and prioritize these chemicals for risk assessment and risk management purposes are insufficient. There are also concerns that effects on the mammary gland have been largely ignored by regulatory agencies. Here, we provide technical guidance that is intended to enhance collection and evaluation of the mammary gland in mice and rats. We review several features of studies that should be controlled to properly evaluate the mammary gland, and then describe methods to appropriately collect the mammary gland from rodents. Furthermore, we discuss methods for preparing whole mounted mammary glands and numerous approaches that are available for the analysis of these samples. Finally, we conclude with several examples where analysis of the mammary gland revealed effects of environmental toxicants at low doses. Our work argues that the rodent mammary gland should be considered in chemical safety, hazard and risk assessments. It also suggests that improved measures of mammary gland outcomes, such as those we present in this review, should be included in the standardized methods evaluated by regulatory agencies such as the test guidelines used for identifying reproductive and developmental toxicants.

Impaired Lactation: Review of Delayed Lactogenesis and Insufficient Lactation

It is estimated that as many as 1 in 20 women worldwide are unable to successfully breastfeed or provide adequate nutrition for their infants through their breast milk alone. Compromised nutrition in the early stages of life places the infant at risk for insufficient growth as well as serious and potentially disabling or life-threatening complications. This review summarizes risk factors associated with impaired lactation that may result in either delayed lactogenesis or insufficient lactation. The risk factors for insufficient lactation are categorized into preglandular, glandular, and postglandular causes. Impaired lactation can occur despite maternal motivation, knowledge, support, and appropriate breastfeeding technique. Although there is no clear way to predict who will experience impaired lactation, knowledge about the risk factors can enable health care professionals to better identify at-risk mother-infant dyads. Early intervention may help prevent infant complications associated with inadequate nutritional intake.

Endocrine disrupting chemicals and the mammary gland

Development of the mammary gland requires coordination of hormone signaling pathways including those mediated by estrogen, progesterone, androgen and prolactin receptors. These hormones play important roles at several distinct stages of life including embryonic/fetal development, puberty, pregnancy, lactation, and old age. This also makes the gland sensitive to perturbations from environmental agents including endocrine disrupting chemicals (EDCs). Although there is evidence from human populations of associations between EDCs and disruptions to breast development and lactation, these studies are often complicated by the timing of exposure assessments and the latency to develop breast diseases (e.g., years to decades). Rodents have been instrumental in providing insights-not only to the basic biology and endocrinology of the mammary gland, but to the effects of EDCs on this tissue at different stages of development. Studies, mostly but not exclusively, of estrogenic EDCs have shown that the mammary gland is a sensitive tissue, that exposures during perinatal development can produce abnormal mammary structures (e.g., alveolar buds, typically seen in pregnant females) in adulthood; that exposures during pregnancy can alter milk production; and that EDC exposures can enhance the response of the mammary tissue to hormones and chemical carcinogens. Other studies of persistent organic pollutants have shown that EDC exposures during critical windows of development can delay development of the gland, with lifelong consequences for the individual. Collectively, this work continues to support the conclusion that EDCs can harm the mammary gland, with effects that depend on the period of exposure and the period of evaluation.

Modern, exogenous exposures associated with altered mammary gland development: A systematic review

BACKGROUND

Many women report low milk supply as the reason for premature breastfeeding cessation. Altered mammary gland development may impact a woman's lactation ability.

OBJECTIVE

This review identifies modern exogenous exposures which alter mammary gland development during embryonic life, puberty and pregnancy.

METHODS

A systematic review was undertaken whereby Medline, CINAHL and Embase articles published from January 1, 2005 to November 20, 2020 were searched using the keywords puberty or embry* or fetal or foetal or foetus or fetus or pregnan* or gestation* AND "mammary gland development" or "breast development" or "mammary development" or "mammary gland function" or "mammary function" or "insufficient glandular tissue" or "mammary hypoplasia" or "breast hypoplasia" or "mammary gland hypoplasia" or "tubular breast*" or "tuberous breast*" or "glandular tissue" or "breast composition" or "mammary composition" or "mammary gland composition". After initial screening of 1207 records, 60 full texts were assessed for eligibility; 6 were excluded due to lack of information about exposure or outcome, leaving 54 studies.

RESULTS

The review included results from 52 animal (rats and mice, monkeys, rabbits, sheep, goats pigs and cows) and 2 human studies. Various endocrine disrupting chemicals and an obesogenic diet were found to be associated with altered mammary gland morphology during key development stages.

CONCLUSIONS

To improve lactation outcomes, future studies need to focus on lactation as the endpoint and be conducted in a standardised manner to allow for a more significant contribution to the literature that allows for better comparison across studies.

Oral galactagogues (natural therapies or drugs) for increasing breast milk production in mothers of non-hospitalised term infants

BACKGROUND

Many women express concern about their ability to produce enough milk, and insufficient milk is frequently cited as the reason for supplementation and early termination of breastfeeding. When addressing this concern, it is important first to consider the influence of maternal and neonatal health, infant suck, proper latch, and feeding frequency on milk production, and that steps be taken to correct or compensate for any contributing issues. Oral galactagogues are substances that stimulate milk production. They may be pharmacological or non-pharmacological (natural). Natural galactagogues are usually botanical or other food agents. The choice between pharmacological or natural galactagogues is often influenced by familiarity and local customs. Evidence for the possible benefits and harms of galactagogues is important for making an informed decision on their use.

OBJECTIVES

To assess the effect of oral galactagogues for increasing milk production in non-hospitalised breastfeeding mother-term infant pairs.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register, ClinicalTrials.gov, the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP), Health Research and Development Network - Phillippines (HERDIN), Natural Products Alert (Napralert), the personal reference collection of author LM, and reference lists of retrieved studies (4 November 2019).

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs (including published abstracts) comparing oral galactagogues with placebo, no treatment, or another oral galactagogue in mothers breastfeeding healthy term infants. We also included cluster-randomised trials but excluded cross-over trials.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane Pregnancy and Childbirth methods for data collection and analysis. Two to four review authors independently selected the studies, assessed the risk of bias, extracted data for analysis and checked accuracy. Where necessary, we contacted the study authors for clarification.

MAIN RESULTS

Forty-one RCTs involving 3005 mothers and 3006 infants from at least 17 countries met the inclusion criteria. Studies were conducted either in hospitals immediately postpartum or in the community. There was considerable variation in mothers, particularly in parity and whether or not they had lactation insufficiency. Infants' ages at commencement of the studies ranged from newborn to 6 months. The overall certainty of evidence was low to very low because of high risk of biases (mainly due to lack of blinding), substantial clinical and statistical heterogeneity, and imprecision of measurements. Pharmacological galactagogues Nine studies compared a pharmacological galactagogue (domperidone, metoclopramide, sulpiride, thyrotropin-releasing hormone) with placebo or no treatment. The primary outcome of proportion of mothers who continued breastfeeding at 3, 4 and 6 months was not reported. Only one study (metoclopramide) reported on the outcome of infant weight, finding little or no difference (mean difference (MD) 23.0 grams, 95% confidence interval (CI) -47.71 to 93.71; 1 study, 20 participants; low-certainty evidence). Three studies (metoclopramide, domperidone, sulpiride) reported on milk volume, finding pharmacological galactagogues may increase milk volume (MD 63.82 mL, 95% CI 25.91 to 101.72; I² = 34%; 3 studies, 151 participants; low-certainty evidence). Subgroup analysis indicates there may be increased milk volume with each drug, but with varying CIs. There was limited reporting of adverse effects, none of which could be meta-analysed. Where reported, they were limited to minor complaints, such as tiredness, nausea, headache and dry mouth (very low-certainty evidence). No adverse effects were reported for infants. Natural galactagogues Twenty-seven studies compared natural oral galactagogues (banana flower, fennel, fenugreek, ginger, ixbut, levant cotton, moringa, palm dates, pork knuckle, shatavari, silymarin, torbangun leaves or other natural mixtures) with placebo or no treatment. One study (Mother's Milk Tea) reported breastfeeding rates at six months with a concluding statement of "no significant difference" (no data and no measure of significance provided, 60 participants, very low-certainty evidence). Three studies (fennel, fenugreek, moringa, mixed botanical tea) reported infant weight but could not be meta-analysed due to substantial clinical and statistical heterogeneity (I² = 60%, 275 participants, very low-certainty evidence). Subgroup analysis shows we are very uncertain whether fennel or fenugreek improves infant weight, whereas moringa and mixed botanical tea may increase infant weight compared to placebo. Thirteen studies (Bu Xue Sheng Ru, Chanbao, Cui Ru, banana flower, fenugreek, ginger, moringa, fenugreek, ginger and turmeric mix, ixbut, mixed botanical tea, Sheng Ru He Ji, silymarin, Xian Tong Ru, palm dates; 962 participants) reported on milk volume, but meta-analysis was not possible due to substantial heterogeneity (I² = 99%). The subgroup analysis for each intervention suggested either benefit or little or no difference (very low-certainty evidence). There was limited reporting of adverse effects, none of which could be meta-analysed. Where reported, they were limited to minor complaints such as mothers with urine that smelled like maple syrup and urticaria in infants (very low-certainty evidence). Galactagogue versus galactagogue Eight studies (Chanbao; Bue Xue Sheng Ru, domperidone, moringa, fenugreek, palm dates, torbangun, moloco, Mu Er Wu You, Kun Yuan Tong Ru) compared one oral galactagogue with another. We were unable to perform meta-analysis because there was only one small study for each match-up, so we do not know if one galactagogue is better than another for any outcome.

AUTHORS' CONCLUSIONS

Due to extremely limited, very low certainty evidence, we do not know whether galactagogues have any effect on proportion of mothers who continued breastfeeding at 3, 4 and 6 months. There is low-certainty evidence that pharmacological galactagogues may increase milk volume. There is some evidence from subgroup analyses that natural galactagogues may benefit infant weight and milk volume in mothers with healthy, term infants, but due to substantial heterogeneity of the studies, imprecision of measurements and incomplete reporting, we are very uncertain about the magnitude of the effect. We are also uncertain if one galactagogue performs better than another. With limited data on adverse effects, we are uncertain if there are any concerning adverse effects with any particular galactagogue; those reported were minor complaints. High-quality RCTs on the efficacy and safety of galactagogues are urgently needed. A set of core outcomes to standardise infant weight and milk volume measurement is also needed, as well as a strong basis for the dose and dosage form used.

Conserved and variable: Understanding mammary stem cells across species

Postnatal mammary gland development requires the presence of mammary stem and progenitor cells (MaSC), which give rise to functional milk-secreting cells and regenerate the mammary epithelium with each cycle of lactation. These long-lived, tissue-resident MaSC are also targets for malignant transformation and may be cancer cells-of-origin. Consequently, MaSC are extensively researched in relation to their role and function in development, tissue regeneration, lactation, and breast cancer. The basic structure and function of the mammary gland are conserved among all mammalian species, from the most primitive to the most evolved. However, species vary greatly in their lactation strategies and mammary cancer incidence, making MaSC an interesting focus for comparative research. MaSC have been characterized in mice, to a lesser degree in humans, and to an even lesser degree in few additional mammals. They remain uncharacterized in most mammalian species, including "ancient" monotremes, marsupials, wild, and rare species, as well as in common and domestic species such as cats. Identification and comparison of MaSC across a large variety of species, particularly those with extreme lactational adaptations or low mammary cancer incidence, is expected to deepen our understanding of development and malignancy in the mammary gland. Here, we review the current status of MaSC characterization across species, and underline species variations in lactation and mammary cancer through which we may learn about the role of MaSC in these processes. © 2017 International Society for Advancement of Cytometry.

Hormonal and Neuromuscular Responses to Breastfeeding: A Pilot Study

OBJECTIVES

Difficult breastfeeding in the first weeks after birth may result in muscle tension in infants and activation of the maternal hypothalamic-pituitary-adrenal (HPA) axis and sympathetic nervous system (SNS). Our primary objective was to examine the feasibility of collecting neuroendocrine markers of maternal HPA axis and SNS activation (salivary cortisol and α-amylase [sAA]) and electromyographic (EMG) markers of infant distress during feeding in the first 2 weeks after birth. We also examined the relationships of these indices to each other and to mother-infant interactive behaviors during feeding.

METHODS

We recruited mothers in the postpartum unit of a teaching hospital and observed a feeding in the dyad's home. Cortisol and sAA were sampled before feeding, 10 min into feeding, at feeding end, and 20 min after feeding. Infant muscle activity was recorded continuously with an EMG data logger. We used the Nursing Child Assessment Feeding Scale to measure mother-infant interaction.

RESULTS

The 20 mothers reported no disruption to breastfeeding and no change in infant behavior due to collection measures. Mean cortisol levels decreased significantly; there was no significant change in sAA levels. Relationships were found between interactive behavior and trends in neuroendocrine biomarkers. Longer bursts of infant muscle activity were associated with higher levels of maternal cortisol during feeding but not mother-infant interactive behaviors.

CONCLUSIONS

Maternal salivary biomarkers and their association with feeding behaviors can be a useful tool for clinical longitudinal research beginning soon after birth. Infant EMG data may be useful for assessing maternal arousal.

Low milk supply and the pediatrician

PURPOSE OF REVIEW

Human milk is the optimal food for human infants, and provides many diverse and well described benefits for both mother and infant. Low milk supply, whether perceived or actual, is one of the most common reasons why mothers stop breastfeeding. Breastfeeding mothers often seek out the guidance and support of their pediatrician in evaluating and resolving milk production concerns.

RECENT FINDINGS

Recent evidence supports the importance of breastfeeding for maternal and child health in both developing and developed countries. Lack of knowledge regarding optimal breastfeeding management accounts for the large majority of low milk supply concerns, but there is emerging evidence that impaired glucose tolerance may contribute to intrinsic low milk supply.

SUMMARY

Breastfeeding mother-infant dyads should be followed closely until lactation is well established and the infant is gaining well. Further research is needed to understand the physiologic contributors to low milk supply and to guide evidence-based interventions to optimize maternal success in reaching breastfeeding goals, particularly for women of poorer metabolic health.