Maternal obesity and developmental programming of neuropsychiatric disorders: An inflammatory hypothesis

Maternal obesity: sex-specific in utero changes in fetal brain autophagy and mTOR

OBJECTIVE

Maternal obesity affects 39.7% of reproductive-age women in the United States. Emerging research has suggested that in utero exposure to maternal obesity is associated with adverse neurodevelopmental outcomes, but knowledge of underlying mechanisms in human samples is lacking.

METHODS

A matched case-control study was performed in women with singleton fetuses who were undergoing elective pregnancy termination at gestational ages 15 to 21 weeks. Maternal adiponectin levels from plasma were measured using ELISA kits. RNA was extracted from fetal brain tissue using RNeasy Mini Kit (QIAGEN). mRNA expression from ADIPOR1, ADIPOR2, MTOR, ATG5, ATG7, BECN1, and MAP1LC3B was quantified through the ΔΔCt method and using GAPDH as a housekeeping gene.

RESULTS

We have identified transcription patterns associated with inhibition of autophagy in male fetal brain tissue exposed to maternal obesity (↑MTOR, ↓ATG5, ↓ATG7, and ↓MAP1LC3B), with female fetuses demonstrating either no change in transcription or nonsignificant changes associated with increased autophagy. There was significant downregulation of the autophagy-associated gene BECN1 in both male and female individuals who were exposed to obesity in utero.

CONCLUSIONS

We present novel evidence suggesting that in utero exposure to maternal obesity in humans may significantly affect neurodevelopment, especially in male fetuses, through alterations in normal autophagy molecular mechanisms and with adiponectin as a potential mediator.

When autophagy meets placenta development and pregnancy complications

Autophagy is a common biological phenomenon in eukaryotes that has evolved and reshaped to maintain cellular homeostasis. Under the pressure of starvation, hypoxia, and immune damage, autophagy provides energy and nutrients to cells, which benefits cell survival. In mammals, autophagy is an early embryonic nutrient supply system involved in early embryonic development, implantation, and pregnancy maintenance. Recent studies have found that autophagy imbalance in placental tissue plays a key role in the occurrence and development of pregnancy complications, such as gestational hypertension, gestational obesity, premature birth, miscarriage, and intrauterine growth restriction. This mini-review summarizes the molecular mechanism of autophagy regulation, the autophagy pathways, and related factors involved in placental tissue and comprehensively describes the role of autophagy in pregnancy complications.

Maternal Thyroid Dysfunction During Pregnancy as an Etiologic Factor in Autism Spectrum Disorder: Challenges and Opportunities for Research

Background: Autism spectrum disorder (ASD) is a neurodevelopmental condition with unknown etiology. Both genetic and environmental factors have been associated with ASD. Environmental exposures during the prenatal period may play an important role in ASD development. This narrative review critically examines the evidence for a relationship between maternal thyroid dysfunction during pregnancy and ASD in the child. Summary: Studies that assessed the associations of hypothyroidism, hyperthyroidism, hypothyroxinemia, thyroid hormone concentrations, or autoimmune thyroid disease with ASD outcomes were included. Most research focused on the relationship between hypothyroidism and ASD. Multiple population-based studies found that maternal hypothyroidism was associated with higher likelihood of an ASD diagnosis in offspring. Associations with other forms of maternal thyroid dysfunction were less consistent. Findings may have been affected by misclassification bias, survival bias, or publication bias. Studies using medical records may have misclassified subclinical thyroid dysfunction as euthyroidism. Two studies that assessed children at early ages may have misclassified those with ASD as typically developing. Most studies adjusted for maternal body mass index (BMI) and/or mental illness, but not interpregnancy interval or pesticide exposure, all factors associated with fetal survival and ASD. Most studies reported a combination of null and statistically significant findings, although publication bias is still possible. Conclusions: Overall, evidence supported a positive association between maternal thyroid dysfunction during pregnancy and ASD outcomes in the child, especially for hypothyroidism. Future studies could reduce misclassification bias by using laboratory measures instead of medical records to ascertain thyroid dysfunction and evaluating children for ASD at an age when it can be reliably detected. Survival bias could be further mitigated by adjusting models for more factors associated with fetal survival and ASD. Additional research is needed to comprehensively understand the roles of maternal levothyroxine treatment, iodine deficiency, or exposure to thyroid-disrupting compounds in the relationship between maternal thyroid dysfunction and child ASD outcomes.

Hofbauer cells and fetal brain microglia share transcriptional profiles and responses to maternal diet-induced obesity

Maternal immune activation is associated with adverse offspring neurodevelopmental outcomes, many mediated by in utero microglial programming. As microglia remain inaccessible throughout development, identification of noninvasive biomarkers reflecting fetal brain microglial programming could permit screening and intervention. We used lineage tracing to demonstrate the shared ontogeny between fetal brain macrophages (microglia) and fetal placental macrophages (Hofbauer cells) in a mouse model of maternal diet-induced obesity, and single-cell RNA-seq to demonstrate shared transcriptional programs. Comparison with human datasets demonstrated conservation of placental resident macrophage signatures between mice and humans. Single-cell RNA-seq identified common alterations in fetal microglial and Hofbauer cell gene expression induced by maternal obesity, as well as sex differences in these alterations. We propose that Hofbauer cells, which are easily accessible at birth, provide novel insights into fetal brain microglial programs, and may facilitate the early identification of offspring vulnerable to neurodevelopmental disorders in the setting of maternal exposures.

Bdnf-Nrf-2 crosstalk and emotional behavior are disrupted in a sex-dependent fashion in adolescent mice exposed to maternal stress or maternal obesity

Maternal obesity has been recognized as a stressor affecting the developing fetal brain, leading to long-term negative outcomes comparable to those resulting from maternal psychological stress, although the mechanisms have not been completely elucidated. In this study, we tested the hypothesis that adverse prenatal conditions as diverse as maternal stress and maternal obesity might affect emotional regulation and stress response in the offspring through common pathways, with a main focus on oxidative stress and neuroplasticity. We contrasted and compared adolescent male and female offspring in two mouse models of maternal psychophysical stress (restraint during pregnancy - PNS) and maternal obesity (high-fat diet before and during gestation - mHFD) by combining behavioral assays, evaluation of the hypothalamic-pituitary-adrenal (HPA) axis reactivity, immunohistochemistry and gene expression analysis of selected markers of neuronal function and neuroinflammation in the hippocampus, a key region involved in stress appraisal. Prenatal administration of the antioxidant N-acetyl-cysteine (NAC) was used as a strategy to protect fetal neurodevelopment from the negative effects of PNS and mHFD. Our findings show that these two stressors produce overlapping effects, reducing brain anti-oxidant defenses (Nrf-2) and leading to sex-dependent impairments of hippocampal Bdnf expression and alterations of the emotional behavior and HPA axis functionality. Prenatal NAC administration, by restoring the redox balance, was able to exert long-term protective effects on brain development, suggesting that the modulation of redox pathways might be an effective strategy to target common shared mechanisms between different adverse prenatal conditions.

Maternal suboptimal selenium intake and low-level lead exposure affect offspring's microglial immune profile and its reactivity to a subsequent inflammatory hit

Micronutrients such as selenium (Se) are essentials since prenatal life to support brain and cognitive development. Se deficiency, which affects up to 1 billion people worldwide, can interact with common adverse environmental challenges including (Pb), exacerbating their toxic effects. Exploiting our recently validated rat model of maternal Se restriction and developmental low Pb exposure, our aims were to investigate: (i) the early consequences of suboptimal Se intake and low-Pb exposure on neuroinflammation in neonates' whole brains; (ii) the potential priming effect of suboptimal Se and low-Pb exposure on offspring's glial reactivity to a further inflammatory hit. To these aims female rats were fed with suboptimal (0.04 mg/kg; Subopt) and optimal (0.15 mg/kg; Opt) Se dietary levels throughout pregnancy and lactation and exposed or not to environmentally relevant Pb dose in drinking water (12.5 µg/mL) since 4 weeks pre-mating. We found an overall higher basal expression of inflammatory markers in neonatal brains, as well as in purified microglia and organotypic hippocampal slice cultures, from the Subopt Se offspring. Subopt/Pb cultures were highly activated than Subopt cultures and showed a higher susceptibility to the inflammatory challenge lipopolysaccharide than cultures from the Opt groups. We demonstrate that even a mild Se deficiency and low-Pb exposure during brain development can influence the neuroinflammatory tone of microglia, exacerbate the toxic effects of Pb and prime microglial reactivity to subsequent inflammatory stimuli. These neuroinflammatory changes may be responsible, at least in part, for adverse neurodevelopmental outcomes.

Obesity in pregnancy-Long-term effects on offspring hypothalamic-pituitary-adrenal axis and associations with placental cortisol metabolism: A systematic review

Obesity, affecting one in three pregnant women worldwide, is not only a major obstetric risk factor. The resulting low-grade inflammation may have a long-term impact on the offspring's HPA axis through dysregulation of maternal, placental and fetal corticosteroid metabolism, and children born of obese mothers have increased risk of diabetes and cardiovascular disease. The long-term effects of maternal obesity on offspring neurodevelopment are, however, undetermined and could depend on the specific effects on placental and fetal cortisol metabolism. This systematic review evaluates how maternal obesity affects placental cortisol metabolism and the offspring's HPA axis. Pubmed, Embase and Scopus were searched for original studies on maternal BMI, obesity, and cortisol metabolism and transfer. Fifteen studies were included after the screening of 4556 identified records. Studies were small with heterogeneous exposures and outcomes. Two studies found that maternal obesity reduced placental HSD11β2 activity. In one study, umbilical cord blood cortisol levels were affected by maternal BMI. In three studies, an altered cortisol response was consistently seen among offspring in childhood (n = 2) or adulthood (n = 1). Maternal BMI was not associated with placental HSD11β1 or HSD11β2 mRNA expression, or placental HSD11β2 methylation. In conclusion, high maternal BMI is associated with reduced placental HSD11β2 activity and a dampened cortisol level among offspring, but the data is sparse. Further investigations are needed to clarify whether the HPA axis is affected by prenatal factors including maternal obesity and investigate if adverse effects can be ameliorated by optimising the intrauterine environment.

Maternal early pregnancy body mass index and bipolar disorder in the offspring

OBJECTIVES

To investigate the association between maternal early pregnancy body mass index (BMI) and offspring bipolar disorder (BPD).

METHODS

We conducted a nationwide cohort study among 1,507,056 non-malformed singleton live-births in Sweden born 1983-2004. Using national registries with prospectively recorded information, we followed participants for a BPD diagnosis from ages 13 to up to 35 years. We compared BPD risks by early pregnancy BMI using hazard ratios (HR) with 95% confidence intervals (CI) from adjusted Cox models. We also conducted sibling-controlled analyses among 874,047 full siblings.

RESULTS

There were 9970 BPD diagnoses. Risk of BPD was 0.72% through 25 years of age. Maternal early pregnancy BMI was positively associated with offspring BPD risk. Compared with normal BMI (18.5-24.9), adjusted HR (95% CI) for overweight (BMI 25-29.9), obesity grade 1 (BMI 30-34.9), and obesity grades 2-3 (BMI ≥35) were 1.08 (1.02, 1.15), 1.26 (1.14, 1.40), and 1.31 (1.07, 1.60), respectively. Adjusted HR per unit BMI was 1.015 (95% CI 1.009, 1.021). A similar trend was observed among siblings. Pregnancy and neonatal complications did not substantially mediate the association between maternal obesity (BMI ≥30) and offspring BPD.

CONCLUSIONS

Maternal BMI ≥25 is associated with offspring BPD risk in a dose-response manner.

Fetal cortical development and neurosonographic findings in obese pregnant women: a case control study from a tertiary hospital

PURPOSE

To investigate the effect of obesity on fetal cortical development.

METHODS

This prospective cross-sectional study was conducted with 91 pregnant women. Fetal neurosonography scans were performed in the third trimester, and according to body mass index (BMI) values, the patients were evaluated in two groups: obese (BMI ≥ 30 kg/m2) and normal weight (BMI < 30 kg/m2). During neurosonography, fetal insular depth and Sylvian fissures, parieo-occipital and cingulate fissure depth, frontal lobe length, and the sizes of the corpus callosum and cavum septum pellucidum were measured using a transvaginal approach. Fetal cortical development and Sylvian fissure operculization were graded.

RESULTS

The number of patients with grade 2 fetal cortical development was significantly higher among the pregnant women in the obese group compared to the normal weight group (n = 17, 41.5% and n = 8, 16.0%, respectively; p = 0.007). In the obese group, the number of pregnant women with grade 4 or below fetal Sylvian fissure operculization was significantly higher (n = 13, 31.7%), and the number of those with grade 9 or above operculization was significantly lower (n = 1, 2.5%) (p = 0.003). The fetal insular depth, frontal lobe anterior-posterior diameter, cingulate fissure depth, and corpus callosum thickness were lower in the obese group, albeit with no significant difference. Parieto-occipital depth significantly decreased in the obese group [6.8 (6) mm)] compared to the control group [10.5 (7.2) mm)] (p = 0.008). The fetal Sylvian fissure ratio and the cavum septum pellucidum ratio were found to be similar between the groups.

CONCLUSION

The data obtained from this study showed that obesity caused fetal cortical changes in pregnant women.

The contributions of parental lactation on offspring development: It's not udder nonsense!

The Developmental Origins of Health and Disease (DOHaD) hypothesis describes how maternal stress exposures experienced during critical periods of perinatal life are linked to altered developmental trajectories in offspring. Perinatal stress also induces changes in lactogenesis, milk volume, maternal care, and the nutritive and non-nutritive components of milk, affecting short and long-term developmental outcomes in offspring. For instance, selective early life stressors shape the contents of milk, including macro/micronutrients, immune components, microbiota, enzymes, hormones, milk-derived extracellular vesicles, and milk microRNAs. In this review, we highlight the contributions of parental lactation to offspring development by examining changes in the composition of breast milk in response to three well-characterized maternal stressors: nutritive stress, immune stress, and psychological stress. We discuss recent findings in human, animal, and in vitro models, their clinical relevance, study limitations, and potential therapeutic significance to improving human health and infant survival. We also discuss the benefits of enrichment methods and support tools that can be used to improve milk quality and volume as well as related developmental outcomes in offspring. Lastly, we use evidence-based primary literature to convey that even though select maternal stressors may modulate lactation biology (by influencing milk composition) depending on the severity and length of exposure, exclusive and/or prolonged milk feeding may attenuate the negative in utero effects of early life stressors and promote healthy developmental trajectories. Overall, scientific evidence supports lactation to be protective against nutritive and immune stressors, but the benefits of lactation in response to psychological stressors need further investigation.

Environmental Enrichment Protects against Neurotoxic Effects of Lipopolysaccharide: A Comprehensive Overview

Neuroinflammation is a pathophysiological condition associated with damage to the nervous system. Maternal immune activation and early immune activation have adverse effects on the development of the nervous system and cognitive functions. Neuroinflammation during adulthood leads to neurodegenerative diseases. Lipopolysaccharide (LPS) is used in preclinical research to mimic neurotoxic effects leading to systemic inflammation. Environmental enrichment (EE) has been reported to cause a wide range of beneficial changes in the brain. Based on the above, the purpose of the present review is to describe the effects of exposure to EE paradigms in counteracting LPS-induced neuroinflammation throughout the lifespan. Up to October 2022, a methodical search of studies in the literature, using the PubMed and Scopus databases, was performed, focusing on exposure to LPS, as an inflammatory mediator, and to EE paradigms in preclinical murine models. On the basis of the inclusion criteria, 22 articles were considered and analyzed in the present review. EE exerts sex- and age-dependent neuroprotective and therapeutic effects in animals exposed to the neurotoxic action of LPS. EE’s beneficial effects are present throughout the various ages of life. A healthy lifestyle and stimulating environments are essential to counteract the damages induced by neurotoxic exposure to LPS.

Non-Linear and Sex-Specific Effect of Maternal Pre-Pregnancy BMI on Emotional and Behavioral Development of Preschool Children: A Population-Based Cohort Study

(1) Background: The aim was to examine the non-linear and sex-specific outcomes of maternal pre-pregnancy BMI on emotional and behavioral development of preschool children; (2) Methods: This study was based on the China-Anhui Birth Cohort (C-ABCS), including 3648 mother-child pairs. Maternal pre-pregnancy BMI was calculated from the maternal pre-pregnancy height and weight measured at the first antenatal checkup. Main caregivers completed the Strengths and Difficulties Questionnaire (SDQ) to assess children's preschool emotional and behavioral development. A restricted cubic spline model was drawn using Stata version 15.1 to analyze the association between maternal pre-pregnancy BMI and preschoolers' SDQ scores by sex; (3) Results: Among boys, maternal pre-pregnancy underweight was associated with the increased risk of conduct problems and pro-social behaviors, and pre-pregnancy overweight/obesity related with the increased risk of peer problems. Interestingly, when maternal pre-pregnancy BMI was between 18.50 kg/m² and 18.67 kg/m², boys had the increased risk of conduct problems. When pre-pregnancy BMI was between 18.50 kg/m² and 19.57 kg/m², boys had the increased risk of pro-social problems. No significant associations were observed; (4) Conclusions: A non-linear effect of maternal pre-pregnancy BMI on emotional and behavioral development has been found in preschool boys. In particular, pre-pregnancy normal weight may still affect boys' emotional and behavioral development.

Longitudinal phenotyping of maternal antenatal depression in obese pregnant women supports multiple-hit hypothesis for fetal brain development, a secondary analysis of the UPBEAT study

BACKGROUND

Maternal antenatal depression is associated with offspring psychological disorders, but obesity is also widely implicated in maternal depression and neurodevelopment. In pregnant women with obesity we explored interrelationships between antenatal depressive symptom trajectories and multiple exposures implicated in fetal neurodevelopment which could explain these associations, as a prelude to exploring associations with infant mental health.

METHODS

The UK Pregnancies Better Eating and Activity Trial (UPBEAT) recruited multi-ethnic pregnant women with obesity (BMI >= 30kg/m²) between March 2009 and June 2014 from 8 UK sites and 1369 were included to model longitudinal antenatal depressive symptoms from Edinburgh Postnatal Depression Scale (EPDS) scores using Latent Class Growth Analysis. Classes were compared on maternal baseline demography, biomarkers of metabolism, inflammation and placental function, infection, diet and by pregnancy and birth outcomes. Odds ratios, mean differences and 95% Confidence Intervals were calculated using robust auxiliary modelling techniques.

FINDINGS

The chosen model produced four classes: "Not Depressed" (n=575 [42%], "reference"), "Mild" (n=523 [37·5%]), "Moderate" (n=219 [16%]) and "Severe" (n=62 [4·5%]) symptom trajectories. Socio-economic deprivation and ethnic diversity were greater in Severe and Moderate classes. Dietary glycaemic load and saturated fat intake were higher in Severe and Moderate classes (at 17 and 27 weeks). Higher Interleukin-6, glycoprotein acetyls (17 weeks), glucose (34 weeks) and lower placental growth factor (PlGF, 17 and 27 weeks) was found in the Severe class. PlGF was lower in the Moderate class (27 weeks). Infection was least likely in the Not Depressed class across gestation. Risks of preterm birth were associated with Severe depressive symptoms (aOR 3·05[1·11 to 8·36]).

INTERPRETATION

Comprehensive phenotyping exposes important fetal exposures implicated in adverse neurodevelopment, differing by depression class. This study expands substantially on causal models of suboptimal fetal neurodevelopment and offers potential new targets for intervention in obese pregnant women.

FUNDING

JNS was funded by a PhD studentship from the National Institute for Health Research (NIHR) Biomedical Research Centre based at Guy's and St Thomas' NHS Foundation Trust and King's College London. UPBEAT was supported by the European Union's 7th Framework Programme (FP7/2007-2013), project EarlyNutrition; grant agreement no. 289346 and the National Institute for Health Research (NIHR) (UK) Programme Grants for Applied Research Programme (RP-0407-10452), Medical Research Council UK Project Grant (MR/L002477/1). Support was also provided by the Chief Scientist Office Scotland, Guy's and St Thomas' Charity and Tommy's Charity (Registered charity no. 1060508). LP and SLW are funded by Tommy's Charity.

Inflammatory Signatures of Maternal Obesity as Risk Factors for Neurodevelopmental Disorders: Role of Maternal Microbiota and Nutritional Intervention Strategies

Obesity is a main risk factor for the onset and the precipitation of many non-communicable diseases. This condition, which is associated with low-grade chronic systemic inflammation, is of main concern during pregnancy leading to very serious consequences for the new generations. In addition to the prominent role played by the adipose tissue, dysbiosis of the maternal gut may also sustain the obesity-related inflammatory milieu contributing to create an overall suboptimal intrauterine environment. Such a condition here generically defined as “inflamed womb” may hold long-term detrimental effects on fetal brain development, increasing the vulnerability to mental disorders. In this review, we will examine the hypothesis that maternal obesity-related gut dysbiosis and the associated inflammation might specifically target fetal brain microglia, the resident brain immune macrophages, altering neurodevelopmental trajectories in a sex-dependent fashion. We will also review some of the most promising nutritional strategies capable to prevent or counteract the effects of maternal obesity through the modulation of inflammation and oxidative stress or by targeting the maternal microbiota.

Maternal diet and obesity shape offspring central and peripheral inflammatory outcomes in juvenile non-human primates

The obesity epidemic affects 40% of adults in the US, with approximately one-third of pregnant women classified as obese. Previous research suggests that children born to obese mothers are at increased risk for a number of health conditions. The mechanisms behind this increased risk are poorly understood. Increased exposure to in-utero inflammation induced by maternal obesity is proposed as an underlying mechanism for neurodevelopmental alterations in offspring. Utilizing a non-human primate model of maternal obesity, we hypothesized that maternal consumption of an obesogenic diet will predict offspring peripheral (e.g., cytokines and chemokines) and central (microglia number) inflammatory outcomes via the diet's effects on maternal adiposity and maternal inflammatory state during the third trimester. We used structural equation modeling to simultaneously examine the complex associations among maternal diet, metabolic state, adiposity, inflammation, and offspring central and peripheral inflammation. Four latent variables were created to capture maternal chemokines and pro-inflammatory cytokines, and offspring cytokine and chemokines. Model results showed that offspring microglia counts in the basolateral amygdala were associated with maternal diet (β = -0.622, p < 0.01), adiposity (β = 0.593, p < 0.01), and length of gestation (β = 0.164, p < 0.05) but not with maternal chemokines (β = 0.135, p = 0.528) or maternal pro-inflammatory cytokines (β = 0.083, p = 0.683). Additionally, we found that juvenile offspring peripheral cytokines (β = -0.389, p < 0.01) and chemokines (β = -0.298, p < 0.05) were associated with a maternal adiposity-induced decrease in maternal circulating chemokines during the third trimester (β = -0.426, p < 0.01). In summary, these data suggest that maternal diet and adiposity appear to directly predict offspring amygdala microglial counts while maternal adiposity influences offspring peripheral inflammatory outcomes via maternal inflammatory state.

The Influence of Maternal Metabolic State and Nutrition on Offspring Neurobehavioral Development: A Focus on Preclinical Models

The prevalence of both obesity and neurodevelopmental disorders has increased substantially over the last several decades. Early environmental factors, including maternal nutrition and metabolic state during gestation, influence offspring neurodevelopment. Both human and preclinical models demonstrate a link between poor maternal nutrition, altered metabolic state, and risk of behavioral abnormalities in offspring. This review aims to highlight evidence from the current literature connecting maternal nutrition and the associated metabolic changes with neural and behavioral outcomes in the offspring, as well as identify possible mechanisms underlying these neurodevelopmental outcomes. Owing to the highly correlated nature of poor nutrition and obesity in humans, preclinical animal models are important in distinguishing the unique effects of maternal nutrition and metabolic state on offspring brain development. We use a translational lens to highlight results from preclinical animal models of maternal obesogenic diet related to alterations in behavioral and neurodevelopmental outcomes in offspring. Specifically, we aim to highlight results that resemble behavioral phenotypes described in the diagnostic criteria of neurodevelopmental conditions in humans. Finally, we examine the proinflammatory nature of maternal obesity and consumption of a high-fat diet as a mechanism for neurodevelopmental alterations that may alter offspring behavior later in life. It is important that future studies examine potential therapeutic interventions and prevention strategies to interrupt the transgenerational transmission of the disease. Given the tremendous risk to the next generation, changes need to be made to ensure that all pregnant people have access to nutritious food and are informed about the optimal diet for their developing child.

Obesity and Maternal-Placental-Fetal Immunology and Health

Obesity rates in women of childbearing age is now at 29%, according to recent CDC reports. It is known that obesity is associated with oxidative stress and inflammation, including disruptions in cellular function and cytokine levels. In pregnant women who are obese, associated placental dysfunction can lead to small for gestational age (SGA) infants. More frequently, however, maternal obesity is associated with large for gestational age (LGA) newborns, who also have higher incidence of metabolic disease and asthma due to elevated levels of inflammation. In addition, anthropogenic environmental exposures to "endocrine disrupting" and "forever" chemicals affect obesity, as well as maternal physiology, the placenta, and fetal development. Placental function is intimately associated with the control of inflammation during pregnancy. There is a large amount of literature examining the relationship of placental immunology, both cellular and humoral, with pregnancy and neonatal outcomes. Cells such as placental macrophages and NK cells have been implicated in spontaneous miscarriage, preeclampsia, preterm birth, perinatal neuroinflammation, and other post-natal conditions. Differing levels of placental cytokines and molecular inflammatory mediators also have known associations with preeclampsia and developmental outcomes. In this review, we will specifically examine the literature regarding maternal, placental, and fetal immunology and how it is altered by maternal obesity and environmental chemicals. We will additionally describe the relationship between placental immune function and clinical outcomes, including neonatal conditions, autoimmune disease, allergies, immunodeficiency, metabolic and endocrine conditions, neurodevelopment, and psychiatric disorders.