Low-Level Prenatal Toxin Exposures and Breastfeeding Duration: A Prospective Cohort Study

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.

Risk factors for discontinuation of exclusive breast feeding within 1month: a retrospective cohort study in Japan

BACKGROUND

While breastfeeding provides benefits for infants and the mother, many women either do not breastfeed or terminate breastfeeding earlier than recommended. The aim of this analysis was to identify factors associated with early discontinuation of breastfeeding in Japanese women.

METHODS

This study used data from medical records of women delivering a singleton live birth between March 2017 and August 2019 in Iwase General Hospital, Fukushima Prefecture, Japan to assess cessation of breastfeeding by the 1-month postpartum appointment. Demographic (age at birth, and employment status), medical (parity, and physical and mental condition of the mother; and infant medical factors, such as sex, Apgar score, and jaundice, among other), and family factors (husband/partner, family members living at the same house, among others) in 734 women who had initiated breastfeeding during their delivery hospital stay were examined, and multiple logistic regression was used to determine significant predictors of early cessation of exclusive breastfeeding.

RESULTS

Bivariate analysis revealed that women who were primipara, unmarried, exposed to secondhand smoke, and employed; those who smoked before pregnancy; and those who had asthma were more likely to discontinue exclusive breastfeeding than other women. Infant factors associated with discontinuation were lower birthweight, earlier gestational age, neonatal intensive care unit admission, treatment for jaundice, or lower weight gain. Multivariable analysis revealed that primiparity, passive smoking before pregnancy, maternal employment, and neonatal jaundice therapy were associated with discontinuation of breastfeeding.

CONCLUSIONS

In particular, women whose partners smoked before pregnancy may need to be targeted for additional support for breastfeeding.

Endocrine-disrupting chemicals and breastfeeding duration: a review

PURPOSE OF REVIEW

The purpose of this review is to describe epidemiologic and toxicological literature investigating how endocrine-disrupting chemicals (EDCs) affect mammary gland development and function, thereby impacting lactation duration.

RECENT FINDINGS

Perfluoroalkyl and polyfluoroalkyl substances appear to reduce breastfeeding duration through impaired mammary gland development, lactogenesis, and suppressed endocrine signaling. Halogenated aromatic hydrocarbons have differing associations with lactation duration, likely because of the variety of signaling pathways that they affect, pointing to the importance of complex mixtures in epidemiologic studies. Although epidemiologic literature suggests that pesticides and fungicides decrease or have no effect on lactation duration, toxicology literature suggests enhanced mammary gland development through estrogenic and/or antiandrogenic pathways. Toxicological studies suggest that phthalates may affect mammary gland development via estrogenic pathways but no association with lactation duration has been observed. Bisphenol A was associated with decreased duration of breastfeeding, likely through direct and indirect action on estrogenic pathways.

SUMMARY

EDCs play a role in mammary gland development, function, and lactogenesis, which can affect breastfeeding duration. Further research should explore direct mechanisms of EDCs on lactation, the significance of toxicant mixtures, and transgenerational effects of EDCs on lactation.

Subjective Environmental Experiences and Women's Breastfeeding Journeys: A Survival Analysis Using an Online Survey of UK Mothers

Local physical and social environmental factors are important drivers of human health and behaviour. Environmental perception has been linked with both reproduction and parenting, but links between subjective environmental experiences and breastfeeding remain unclear. Using retrospective data from an online survey of UK mothers of children aged 0-24 months, Cox-Aalen survival models test whether negative subjective environmental experiences negatively correlated with any and exclusive breastfeeding (max n = 473). Matching predictions, hazards of stopping any breastfeeding were increased, albeit non-significantly, across the five environmental measures (HR: 1.05-1.26) Hazards for stopping exclusive breastfeeding were however (non-significantly) reduced (HR: 0.65-0.87). Score processes found no significant time-varying effects. However, estimated cumulative coefficient graphs showed that the first few weeks postpartum were most susceptible to environmental influences and that contrary to our predictions, mothers with worse subjective environmental experiences were less likely to stop breastfeeding at this time. In addition, the hazard of stopping exclusive breastfeeding declined over time for mothers who thought that littering was a problem. The predicted increased hazards of stopping breastfeeding were only evident in the later stages of any breastfeeding and only for mothers who reported littering as a problem or that people tended not to know each other. Perceived harsher physical and social environmental conditions are assumed to deter women from breastfeeding, but this may not always be the case. Women's hazards of stopping breastfeeding change over time and there may be particular timepoints in their breastfeeding journeys where subjective environmental experiences play a role.

Oral exposure to lead for Japanese children and pregnant women, estimated using duplicate food portions and house dust analyses

BACKGROUND

Lead is a toxic metal abundant in the environment. Consumption of food contaminated at low levels of lead, especially by small children and pregnant women, raises a health concern.

METHODS

Duplicated food portions and drinking water were collected over 3 days from 88 children and 87 pregnant women in Shimotsuke, Tochigi, Japan. Participants were recruited in this study between January 2014 and October 2015. Dust was also collected from their homes. Lead concentrations were measured and consequent oral lead exposure levels were estimated for this population at high risk to environmental toxicants. Lead concentrations of peripheral and cord blood, taken from children and pregnant women, and were also analyzed.

RESULTS

Lead concentrations in food, drinking water, and house dust were low in general. Oral lead exposure to lead was higher for children (Mean ± SEM; 5.21 ± 0.30 μg/kg BW/week) than in pregnant women (1.47 ± 0.13 μg/kg BW/week). Food and house dust were main sources of lead contamination, but the contribution of house dust widely varied. Means ± SEM of peripheral and cord blood lead concentrations were 0.69 ± 0.04 μg/dL and 0.54 ± 0.05 μg/dL, respectively for pregnant women and 1.30 ± 0.07 μg/dL (peripheral only) in children. We detect no correlation between smoking situations and blood lead concentration in pregnant women.

CONCLUSION

We conclude that oral lead exposure levels for Japanese children and pregnant women were generally low, with higher concentrations and exposure for children than for pregnant women. More efforts are necessary to clarify the sources of lead contamination and reduce lead exposure of the population at high risk even in Japan.

Are mothers less likely to breastfeed in harsh environments? Physical environmental quality and breastfeeding in the Born in Bradford study

We use the United Kingdom's Born in Bradford study to investigate whether women in lower quality environments are less likely to breastfeed. We use measures of physical environmental quality (water disinfectant by-products [DBPs], air pollution, passive cigarette smoke, and household condition) alongside socio-economic indicators, to explore in detail how different exposures influence breastfeeding. Drawing on evolutionary life history theory, we predict that lower environmental quality will be associated with lower odds of initiating, and higher hazards of stopping, breastfeeding. As low physical environmental quality may increase the risk of adverse birth outcomes, which may in turn affect breastfeeding chances, we also test for mediation by gestational age, birthweight, head circumference, and abdominal circumference. Our sample is composed of mothers who gave birth at the Bradford Royal Infirmary in West Yorkshire between March 2007 and December 2010 for whom breastfeeding initiation data was available. Analyses were stratified by the two largest ethnic groups: White British (n = 3,951) and Pakistani-origin (n = 4,411) mothers. After controlling for socio-economic position, Pakistani-origin mothers had lower chances of initiating and higher chances of stopping breastfeeding with increased water DBP exposure (e.g., OR for 0.03-0.61 vs. <0.02 μg/day dibromochloromethane exposure 0.70 [0.58-0.83], HR 1.16 [0.99-1.36]), greater air pollution exposure predicted lower chances of initiation for both ethnic groups (e.g., OR for 10 μg/m³ increase in nitrogen dioxide 0.81 [0.66-0.99] for White British mothers and 0.79 [0.67-0.94] for Pakistani-origin mothers) but also a reduced hazard of stopping breastfeeding for White British mothers (HR 0.65 [0.52-0.80]), and exposure to household damp/mould predicted higher chances of breastfeeding initiation amongst White British mothers (OR 1.66 [1.11-2.47]). We found no evidence that physical environmental quality effects on breastfeeding were mediated through birth outcomes amongst Pakistani-origin mothers and only weak evidence (p < 0.10) amongst White British mothers (exposure to passive cigarette smoke was associated with having lower birthweight infants who were in turn less likely to be breastfed whereas greater air pollution exposure was associated with longer gestations and in turn reduced hazards of stopping breastfeeding). Overall, our findings suggest that there is differential susceptibility to environmental exposures according to ethnicity. Although the water DBP results for Pakistani-origin mothers and air pollution-initiation results for both ethnic groups support our hypothesis that mothers exhibit reduced breastfeeding in poorer quality environments, several physical environmental quality indicators showed null or positive associations with breastfeeding outcomes. We consider physiological explanations for our findings and their implications for life history theory and public health policy.

Secondhand Smoke Exposure During Pregnancy and Mothers' Subsequent Breastfeeding Outcomes: A Systematic Review and Meta-Analysis

Secondhand smoke exposure of non-smoking women during pregnancy is associated with a higher risk of adverse birth outcomes. However, the available evidence regarding the association between expectant mothers’ secondhand smoke exposure and breastfeeding outcomes remains limited. This systematic review aimed to examine associations between secondhand smoke exposure of nonsmoking women during pregnancy with the initiation, prevalence, and duration or breastfeeding compared to women who were breastfeeding and had not been exposed to secondhand smoke. Women who smoked during pregnancy were excluded. We included case-control, cross-sectional, and cohort studies with a comparison control group. Medline CINAHL, and EMBASE were searched in January 2017. After screening 2777 records we included eight prospective cohort studies. The risk of bias assessment tool for non-randomized studies indicated a high risk of outcome assessment blinding. Meta-analysis of two studies established that the odds of discontinuation of any brestfeeding before six months were significantly increased in the secondhand smoke exposed women (pooled odds = 1.07 [95%CI = 1.01, 1.14], two studies, 1382 women). Therefore, secondhand smoke might be associated with discontinuing any breastfeeding before six months. More research is necessary to understand the association between secondhand smoke and the initiation, prevalence and duration of breastfeeding.

The extent and predictors of phthalate exposure among couples undergoing in vitro fertilization treatment

Phthalates are chemicals used as plasticizers and solvents in many consumer products but are suspected of disrupting the endocrine system and are known for their reproductive/developmental health risks. This study examined the extent and predictors of phthalate exposure among 599 couples undergoing in vitro fertilization. A questionnaire was administered to obtain sociodemographic, health, and lifestyle data, and two spot urine samples were collected from the couples to analyze eight phthalate metabolites, cotinine (COT) as a smoking index, and creatinine to adjust for urine dilution. Seven phthalate metabolites were detected in > 94% of the urine samples, and monobenzyl phthalate (MBzP) was found in 24% of the women and 26% of their male partners. Median phthalate levels were highest for monoethyl phthalate (MEP), at 333.26 μg/l in women and 290 μg/l in male partners, and lowest for MBzP, at 1.17 μg/l in women and 1.14 μg/l in male partners. Correlation coefficients of ≥ 0.4 between the women and their male partners for the eight urinary phthalate metabolites may indicate a shared source of exposure. A multivariate regression model was used to assess the association between predictors and each urinary phthalate metabolite. Several potential predictors for the variations in specific urinary phthalate metabolites were identified, including the body mass index, age, socioeconomic status, and regional distribution for both women and their male partners but with slightly different patterns. Women with a history of breastfeeding, using bottled water for cooking and storing food in plastic bags had lower MEP (8.7%), mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP) (9.2%), and both mono-iso-butyl phthalate and MECPP (8.2 and 8.1%). A history of contraceptive use was associated with an increase in MECPP (8.7%), mono-(2-ethyl-5-hydroxyhexyl) phthalate (11.4%), mono-(2-ethyl-5-oxohexyl) phthalate (7.6%), and the molar sum of bis (2-ethylhexyl) phthalate metabolites (8.9%). Urinary COT levels were associated with an increase of 10-16% in all urinary metabolites in women but of only 10.5% in mono-(2-ethylhexyl) phthalate in male partners. More than 95% of the couples reported the use of cosmetics, perfumes, and personal-care products, but we were not able to find associations with urinary phthalate metabolites, perhaps due to their short half-lives. MEP levels associated with the use of household cleaning products were 11.2% higher in male partners. Our levels were generally higher than those reported elsewhere, perhaps due to different lifestyles, cultural practices, dietary habits, use of personal-care products, and governmental legislation.