Oestrogens and progesterone in human milk and their effects on infant health outcomes: A narrative review.

Human milk (HM) is a complex biological system that contains a wide range of bioactive components including oestrogens and progesterone. Whilst maternal oestrogens and progesterone concentrations drop rapidly after birth, they remain detectable in HM across lactation. Phytoestrogens and mycoestrogens, which are produced by plants and fungi, are also present in HM and can interact with oestrogen receptors to interfere with normal hormone functions. Despite the potential impact of HM oestrogens and progesterone on the infant, limited research has addressed their impact on the growth and health of breastfed infants. Furthermore, it is important to comprehensively understand the factors that contribute to these hormone levels in HM, in order to establish effective intervention strategies. In this review, we have summarized the concentrations of naturally occurring oestrogens and progesterone in HM from both endogenous and exogenous sources and discussed both maternal factors impacting HM levels and relationships with infant growth.

Human Milk Sodium and Potassium as Markers of Mastitis in Mothers of Preterm Infants.

Introduction: This prospective longitudinal study examined changes in milk sodium concentration (Na) and sodium:potassium ratio (Na:K), microbiological culture, milk production, and breast health in relation to mastitis after preterm birth. Methods: We studied women who gave birth at 29-34 weeks of gestation in a tertiary obstetric hospital in Perth, Western Australia. Milk samples, 24-hour milk production, and breast health data were collected every second day to day 10 postpartum, then every third day until infant discharge from the neonatal unit. Milk Na and K were measured at point of care (POC) using handheld ion selective meters, and Na:K calculated. Cultures were performed on postnatal days 8, 13, and every 6 days thereafter. For episodes of mastitis, milk was cultured at onset, and Na and Na:K measured daily until resolution. Women were followed up at 4 and 8 weeks postpartum. Results: In a sample of 44 women, 4 mastitis cases were detected in 3 women during their infants' neonatal stay; all had elevated milk Na and Na:K that resolved within 48 hours; 2/4 experienced reduced milk production and 1/4 had heavy growth of Staphylococcus epidermidis. A further 2 mastitis cases were reported in 39 women followed up to 8 weeks postpartum. Four women had elevated milk Na and Na:K without clinical signs of mastitis; three also had reduced milk production. Conclusions: POC testing of milk Na and/or Na:K may offer a useful indicator of breast health. Mastitis may cause an acute reduction in milk production regardless of the presence of culture-positive infection.

Breastfeeding and Maternal Perceptions of Infant Sleep, Settle and Cry Patterns in the First 9 Months.

This study evaluated relationships between maternal perceptions of infant sleep, settling and crying patterns and breastfeeding. A prospective observational study of 91 mothers of healthy, term infants was conducted with follow ups over 9 months after discharge from a Western Australian maternity hospital. Feeding information, sleep, settle and cry behaviours, maternal bother at infant behaviours and confidence were measured using the Sleep and Settle Questionnaire. Breastfeeding confidence was measured using the Breastfeeding Self-Efficacy Scale-Short Form. Questionnaires were administered at 2 and 6 weeks, 3, 6 and 9 months. Linear mixed models were used to assess associations between maternal bother, feeding method and infant characteristics. The feeding method was not associated with maternal bother, and cessation of breastfeeding did not result in a change in bother scores (p = 0.34). Duration of infant crying in the day, evening and night, frequency of night waking and duration of settling to sleep in the day were associated with increased bother scores. Higher breastfeeding self-efficacy and maternal confidence were associated with lower bother scores (both p < 0.01). Maternal bother is associated with infant behaviours that require parental input, but not breastfeeding status. Resources that address parental expectations regarding infant sleep while providing strategies to support maternal wellbeing and breastfeeding are needed.

Maternal Evaluation of a Team-Based Maternity Care Model for Women of Low Obstetric Risk.

In response to the need for affordable and comprehensive maternity care, a multidisciplinary team-based maternity care service led by general practitioners with obstetric training (GPOs) and midwives was established for women of low obstetric risk. We evaluated maternal satisfaction with this model of care. All women that attended the service and gave birth in 2020 were approached. Participants used an online survey to rate their satisfaction with aspects of their pregnancy, hospital stay and postpartum care and were invited to provide additional written feedback. Fifty percent (81/162) of women (33 ± 3.9 years) responded, with 59% primiparous. Proportions of participants that were very satisfied with their overall pregnancy, hospital stay, and postpartum care were 91%, <50%, and 85%, respectively. Both survey and qualitative data identified high satisfaction with emotional care and time afforded to discuss concerns during appointments. High levels of satisfaction can be achieved in women of low obstetric risk through the provision of GPO-midwife led multidisciplinary care throughout the maternity journey.

Exclusively Breastfed Infant Microbiota Develops over Time and Is Associated with Human Milk Oligosaccharide Intakes.

Temporal development of maternal and infant microbiomes during early life impacts short- and long-term infant health. This study aimed to characterize bacterial dynamics within maternal faecal, human milk (HM), infant oral, and infant faecal samples during the exclusive breastfeeding period and to document associations between human milk oligosaccharide (HMO) intakes and infant oral and faecal bacterial profiles. Maternal and infant samples (n = 10) were collected at 2−5, 30, 60, 90 and 120 days postpartum and the full-length 16S ribosomal RNA (rRNA) gene was sequenced. Nineteen HMOs were quantitated using high-performance liquid chromatography. Bacterial profiles were unique to each sample type and changed significantly over time, with a large degree of intra- and inter-individual variation in all sample types. Beta diversity was stable over time within infant faecal, maternal faecal and HM samples, however, the infant oral microbiota at day 2−5 significantly differed from all other time points (all p < 0.02). HMO concentrations and intakes significantly differed over time, and HMO intakes showed differential associations with taxa observed in infant oral and faecal samples. The direct clinical relevance of this, however, is unknown. Regardless, future studies should account for intakes of HMOs when modelling the impact of HM on infant growth, as it may have implications for infant microbiota development.

A brief gestalt intervention changes ultrasound measures of tongue movement during breastfeeding: case series.

BACKGROUND: Lactation consultants frequently advise adjustments to fit and hold (or positioning and attachment) with the aim of optimising intra-oral nipple placement. However, approaches to fit and hold vary widely, with limited evidence of benefits, and effects of fit and hold on infant tongue movement have not been examined. The aim of this preliminary study was to investigate whether a gestalt breastfeeding intervention alters tongue movement, using measurements from ultrasound imaging to determine nipple placement and intra-oral nipple and breast tissue dimensions. METHODS: Ultrasound measurements were conducted in five breastfeeding dyads, infants aged 4-20 weeks, while feeding in their usual or 'standard' position and again after brief application of gestalt principles of fit and hold. Four of the mother-baby pairs, who had received comprehensive lactation support, reported persisting nipple pain. Three of these infants had difficulty latching and fussed at the breast; three had been diagnosed with oral ties. A fifth pair was breastfeeding successfully. RESULTS: Ultrasound demonstrated that the distance from nipple tip to junction of the hard and soft palate decreased, intra-oral nipple and breast tissue dimensions increased, and nipple slide decreased after a brief gestalt intervention. CONCLUSION: These preliminary findings suggest that changes in fit and hold impact on infant tongue movement and contour. Further research investigating short- and long-term outcomes of a gestalt breastfeeding intervention in larger cohorts is required.

Breast Milk Production in Women Who Use Nipple Shields for Persistent Nipple Pain.

OBJECTIVE: To examine relationships between nipple pain scores and 24-hour milk production volumes, breastfeeding and pumping frequencies, and breastfeeding duration in women using nipple shields for persistent nipple pain. DESIGN: Secondary outcome analysis of a prospective cohort study. SETTING: Research laboratory and participants' homes. PARTICIPANTS: Twenty-five breastfeeding women (6 ± 4 weeks after birth) who used nipple shields for persistent nipple pain. METHODS: We conducted a randomized trial to investigate the primary outcome of milk transfer with and without nipple shields among participants with and without nipple pain. Here, we report secondary outcomes of associations between 24-hour milk production, breastfeeding and pumping frequencies, breastfeeding durations, and intake in participants using a nipple shield for nipple pain. Participants completed demographic, health and breastfeeding questionnaires and, at two monitored breastfeeding sessions, completed a pain visual analogue scale and Brief Pain Inventory-Short Form (BPI-SF; total and subscale scores for pain interference with General Activity, Mood, Sleep, and Breastfeeding). Milk production (milliliters per 24 hours), feed volumes, and percentage of available milk removed were calculated from data and milk samples obtained by participants over one 24-hour period and at study visits. Participants logged 24-hour data on a customized research website. We used descriptive statistics as well as simple and multiple linear regression for analyses. RESULTS: Milk production and feeding duration were not associated with nipple pain scores (visual analogue scale: p = .80, BPI-SF: p = .44). An increase in BPI-SF Breastfeeding subscale score of 1 unit, indicating pain interference with breastfeeding, was associated with a 0.28 decrease in 24-hour breastfeeding frequency (p = .02) and an 18.8-ml decrease in 24-hour breastfeeding intake (p = .04). CONCLUSION: Persistent nipple pain was associated with reduced breastfeeding frequency; therefore, continuing professional support is required to ensure adequate milk removal and pain management.

25 Years of Research in Human Lactation: From Discovery to Translation.

Researchers have recently called for human lactation research to be conceptualized as a biological framework where maternal and infant factors impacting human milk, in terms of composition, volume and energy content are studied along with relationships to infant growth, development and health. This approach allows for the development of evidence-based interventions that are more likely to support breastfeeding and lactation in pursuit of global breastfeeding goals. Here we summarize the seminal findings of our research programme using a biological systems approach traversing breast anatomy, milk secretion, physiology of milk removal with respect to breastfeeding and expression, milk composition and infant intake, and infant gastric emptying, culminating in the exploration of relationships with infant growth, development of body composition, and health. This approach has allowed the translation of the findings with respect to education, and clinical practice. It also sets a foundation for improved study design for future investigations in human lactation.

Reproducibility of the creamatocrit technique for the measurement of fat content in human milk.

Quantification of human milk (HM) fat is important for determining the energy intake of infants. The simplest and most rapid method is the creamatocrit method. However, the reliability of the creamatocrit has not been comprehensively investigated. The aims of this study were to test the inter- and-intra-rater reliability of: 1) HM sampling after hand- or-machine mixing methods and 2) HM fat measurement by the creamatocrit method. Inter-and-intra rater HM sampling after hand- or-machine mixing methods had high intraclass correlation coefficient (>0.91). Inter-rater reliability of measurement of HM with low fat (<2%) resulted in high variability (median coefficient of variations (CVs) > 15%). Intra- and inter-rater reliability of measurement of HM with higher fat (>3.5%) had low variability (median CVs < 10%). As the greatest variation in the creamatocrit method occurred during the measurement of HM samples with low fat, duplicate readings are necessary to reduce discrepancies in every HM fat determination.

Nipple shield use does not impact sucking dynamics in breastfeeding infants of mothers with nipple pain.

Nipple shields (shield) may reduce pain during breastfeeding, but the impact on infant sucking dynamics is not known. We examined the effects of shield use on sucking dynamics, milk removal and nipple pain in two groups of breastfeeding dyads: pain group (PG): shield used for nipple pain; comparison group (CG): no breastfeeding difficulties. Twenty PG (6 ± 4 weeks postnatal) and 28 CG dyads (8 ± 6 weeks postnatal) attended 2 monitored breastfeeding sessions with shield use randomised. Within-subject outcomes were compared. PG: shield use did not affect intra-oral vacuum (peak p = 0.17, baseline p = 0.59), sucking frequency (p = 0.20) or milk transfer (40 mL vs 48 mL, p = 0.80; percentage of available milk removed (PAMR) 55% vs 57%, p = 0.88), and reduced McGill pain scores (p = 0.012). CG: shield use increased non-nutritive sucking (10% more, p = 0.049), and reduced nutritive sucking (18% less, p = 0.017) and milk transfer (63 mL vs 31 mL p < 0.001, PAMR 65% vs 36% p < 0.001). For both groups, feeding duration increased by 2 min (p < 0.0001) and non-nutritive portions of the feed increased with shield use.Conclusion: Nipple shield use improved maternal comfort and did not impact milk removal or sucking strength in PG, but significantly reduced milk transfer and nutritive sucking in CG. What is Known: • Mothers report that nipple shields reduce nipple pain and enable continued breastfeeding. • Concerns that nipple shield use may reduce milk transfer and alter infant sucking patterns are based on limited published evidence. What is New: • Nipple shield use is associated with a 25% reduction in pain scores in breastfeeding mothers with chronic nipple pain. • Milk transfer is not reduced in dyads that regularly use a shield for chronic nipple pain. • Intra-oral vacuums are not impacted by nipple shield use in mothers experiencing pain.

Causes of perception of insufficient milk supply in Western Australian mothers.

A perception of insufficient milk supply (PIMS) is associated with early discontinuation of breastfeeding. Ideally, an objective measure of milk supply would either dispel or confirm this perception and provide reassurance or guide professional advice. Clinical signs of sufficient milk intake (steady growth, sufficient elimination, infant alertness and breasts feeling full before breastfeeds and soft after breastfeeds) should provide confidence in milk supply. We surveyed 423 mothers in early lactation who had breastfeeding problems to determine the proportion that had PIMS and to determine if the mothers with PIMS relied on these clinical signs or other perceptions of their infants' behaviour as indications of insufficient milk supply. By 3 weeks after birth, we found that the rate of PIMS among mothers with breastfeeding problems was 44%. Supplementary infant formula was being given to 66% of the infants, so the clinical indications were that milk intake was sufficient, but 74% of the mothers with PIMS cited concerns that their infants did not appear satisfied after breastfeeds. After targeted advice from lactation consultants, mothers with PIMS showed positive changes in their perceptions of their milk supply, underlining the value of professional guidance soon after birth. We conclude that an appearance of infant dissatisfaction is the major cause of PIMS in Western Australia.

Effect of nipple shield use on milk removal: a mechanistic study.

BACKGROUND: Concerns about reduced milk transfer with nipple shield (NS) use are based on evidence from studies with methodological flaws. Milk removal during breastfeeding can be impacted by infant and maternal factors other than NS use. The aim of this study was to control electric breast pump vacuum strength, pattern and duration across multiple study sessions to determine if NS use reduces milk removal from the breast. METHODS: A within-subject study with two groups of breastfeeding mothers (infants < 6 months) were recruited; Control Group (CG): no breastfeeding difficulties; Pain Group (PG) used NS for persistent nipple pain. Mothers completed three randomised 15 min pumping sessions using the Symphony vacuum curve (Medela AG); no NS, fitted NS, and a small NS. Sessions were considered valid where the applied vacuum was within 20 mmHg of the set vacuum. Milk removal was considered as pumped milk volume, and also percentage of available milk removed (PAMR), which is calculated as the pumped volume divided by the estimated milk volume stored in the breast immediately prior to pumping. RESULTS: Of 62 sessions (all: n = 31 paired sessions) a total of 11 paired sessions from both PG (n = 03) and CG (n = 08) were valid (subset) with and without a fitted NS. Only 2 small shield sessions were valid and so all small shield measurements were excluded. Both pumped volumes and PAMR were significantly lower with NS use for all data but not for subset data. (All: Volume and PAMR median: no NS: 76.5 mL, 69%, Fitted NS: 32.1 mL, 41% respectively (volume p = 0.002, PAMR p = 0.002); Subset: Volume and PAMR median: no NS: 83.8 mL, 72%; Fitted NS: 35.2 mL, 40% (volume p = 0.111 and PAMR p = 0.045). The difference in PAMR, but not volume, was statistically significant when analysed by linear mixed modelling. A decrease of 10 mmHg was associated with a 4.4% increase in PAMR (p = 0.017). CONCLUSIONS: This experimental data suggests that nipple shield use may reduce milk removal. Close clinical monitoring of breastfeeding mothers using nipple shields is warranted.

Effect of vacuum-release teat versus standard teat use on feeding milestones and breastfeeding outcomes in very preterm infants: A randomized controlled trial.

BACKGROUND: Breast milk is important to infant health, yet shorter breastfeeding duration is reported for preterm infants. Both breast and bottle feeds are given in the neonatal unit, with full oral feeding often the last milestone to be achieved prior to discharge home. Unlike standard bottle teats, a vacuum release teat requires the application of negative intra-oral pressure to release milk, and so may facilitate breastfeeding in preterm infants. The objective of this study was to determine the effect of vacuum release teat use on timing of achievement of the first full oral feed and on first completion of 24 h full oral feeds. Feeding method at discharge home, 2 weeks, 6 weeks and 12 weeks corrected gestational age were also examined. METHODS: A randomized controlled trial was completed with mothers of preterm infants born 24-33 weeks gestation in the neonatal unit of a tertiary women's hospital. Infants were randomized to one of two parallel groups using a vacuum release teat or standard teat for oral feeds when the mother was not available to breastfeed. Test weights were completed for all oral feeds. It was not possible to blind participants, care givers and outcome assessors to group assignment due to the nature of the study. RESULTS: The groups did not differ with regard to timing of achievement of first full oral feed or 24 h of full oral feeds. Significantly more infants in the vacuum release teat group were exclusively fed breast milk at discharge from hospital and breastfed at 3 months corrected gestational age. CONCLUSIONS: Use of a vacuum release teat when the mother is not available to breastfeed may promote preterm breastfeeding skills, resulting in higher rates of exclusivity and longer breastfeeding duration. TRIAL REGISTRATION: The trial is registered with the Australian New Zealand Clinical Trials Registry ACTRN12615000245594.

Changes in milk composition associated with pethidine-PCEA usage after Caesarean section.

The effect of pethidine as patient-controlled epidural analgesia (PCEA) on specific biochemical components in breast milk in relation to the timing of secretory activation is not well investigated. The aim of this study was to compare biochemical timing of secretory activation between women who had a vaginal (V) or Caesarean birth with pethidine-PCEA (CBP). Several milk samples were collected daily from 36 mothers (17 V, 19 CBP) for the first 265 h post-partum. Protein and lactose concentrations and Na+ and K+ ion levels were measured. Samples were assigned to three time periods: 0-72, >72-165 and >165-265 h post-partum for statistical analyses. Data were analyzed using linear mixed effect models. In the first 72 h post-partum, the mean difference in lactose concentration was 5 gL-1 higher in group V (P < 0.05). From >72-165 h post-partum, protein and Na+ concentrations were lower in group V (P = 0.05, P = 0.02), and K+ levels were higher in group V (P < 0.001). From >165-265 h post-partum, there were no significant differences between the groups. Biochemically, secretory activation had occurred by 72 h post-partum in both groups. There were greater variations in measured biochemical components observed within group CBP initially. However, by 165 h post-partum, there were no differences in the biochemical components between the groups. This suggests that effects of pethidine-PCEA are diminished by 72 h post-partum and undetected by 165 h.

Vacuum characteristics of the sucking cycle and relationships with milk removal from the breast in term infants.

BACKGROUND: The importance of an infant's intra-oral vacuum in milk removal from the breast has been established. However, the relationship between the vacuum curve and milk transfer is not well understood. AIMS: To investigate the parameters of the infant suck cycle in relation to the volume of milk removed from the breast. STUDY DESIGN: Cross-sectional study to elucidate the role of infant intra-oral vacuum in efficient milk removal from the breast. SUBJECTS: Nineteen fully breastfed term infants. METHODS: Intra-oral vacuum was recorded during monitored breastfeeds using a pressure transducer. Ultrasound imaging (milk flow) and respiratory inductive plethysmography (swallowing) were used to determine the nutritive sucking (NS) portion of the feed. Milk intake was determined by weighing infants before and after feeds. Vacuum traces of the first and next 2min of NS from the first breast were analysed. RESULTS: The volumes of milk removed during both NS periods were negatively associated with peak vacuum (p<0.001) and rate of vacuum application (p<0.001), and positively related to area under first half of the suck cycle (p<0.001). Most parameters changed significantly from the first 2min of NS to the next 2min including significant reduction in peak vacuum and area under first half of the suck cycle. CONCLUSION: These results further support the role of intra-oral vacuum, specifically optimal peak vacuum, in effective and efficient milk removal during breastfeeding. It also appears that infants modify their sucking dynamics to adapt to changes in milk flow during milk ejection as the breast empties.

A Case Report of a Breastfed Infant's Excessive Weight Gains over 14 Months.

High infant weight gain is associated with subsequent overweight and obesity and so may contribute to related comorbidities such as metabolic syndrome and cardiovascular disease. The growth acceleration hypothesis proposes that early and rapid growth in infancy can shape the metabolic profile to increase susceptibility to obesity. Although breastfeeding reduces the infant's risk of subsequent overweight and obesity, high infant weight gains are observed in this population. We report the case of an infant with excessive weight gains that persisted throughout 6 months of exclusive breastfeeding. The mother chose to continue breastfeeding despite medical advice to wean, and high weight gains continued for a further 8 months of breastfeeding and complementary foods. This is the first reported case of an exclusively breastfed infant with excessive weight gains (> 97th percentile) with contemporaneous measures of 24-hour breast milk intake and doses and concentrations of protein, fat, and energy. We found a high breast milk protein dose, which is associated with increased weight gain and lean body mass but not necessarily adiposity. It is likely that other influences also contributed to the high infant weight gain. High infant weight gain is multifactorial, with evolving evidence for the role of adipokines and genetic markers. Advice to replace breast milk with formula affects the dose-dependent protection from noncommunicable diseases afforded by breast milk and may not be an effective strategy for reducing adiposity.

Evidence of improved milk intake after frenotomy: a case report.

Ankyloglossia (tongue tie) is a well-recognized cause of breastfeeding difficulties and, if untreated, can cause maternal nipple pain and trauma, ineffective feeding, and poor infant weight gain. In some cases, this condition will result in a downregulation of the maternal milk supply. Milk-production measurements (24-hour) for a breastfeeding infant with ankyloglossia revealed the ineffective feeding of the infant (78 mL/24 hours), and a low milk supply (350 mL/24 hours) was diagnosed. Appropriate management increased milk supply (1254 mL/24 hours) but not infant milk intake (190 mL/24 hours). Test weighing convincingly revealed the efficacy of frenotomy, increasing breastfeeding milk transfer from 190 to 810 mL/24 hours. Postfrenotomy, breastfeeding almost completely replaced bottle-feeding of expressed breast milk. This case study confirms that ankyloglossia may reduce maternal milk supply and that frenotomy can improve milk removal by the infant. Milk-production measurements (24-hour) provided the evidence to confirm these findings.

Breastfeeding frequency, milk volume, and duration in mother-infant dyads with persistent nipple pain.

BACKGROUND: Nipple pain and insufficient milk supply are major causes of early weaning. We have found that persistent nipple pain was associated with strong infant sucking vacuums during breastfeeding. Several studies indicate that nipple pain and abnormal infant sucking have the potential to reduce milk transfer. We aimed to determine whether women with persistent nipple pain had low milk supply. SUBJECTS AND METHODS: The 24-hour milk production and feeding characteristics of mothers with persistent nipple pain (n=21) were compared with those mothers without nipple pain (n=21). Milk productions were measured by test-weighing the infant before and after every feed from each breast over a 24-26-hour period. Comparisons were made using Student's t tests and linear mixed models as appropriate. RESULTS: Lower milk productions were associated with longer meal durations for mothers with pain. There were no significant differences in the average 24-hour milk production or any feeding characteristics between the groups. However, four women with persistent nipple pain had milk production levels below 500 mL/day. CONCLUSIONS: The majority of breastfeeding women experiencing persistent nipple pain were able to achieve normal milk production levels. Feeding duration and frequency were similar to those of women not experiencing pain. However, longer meal durations in the pain group were associated with lower levels of milk production. Further investigation is necessary to identify mothers most affected by maternal nipple pain.