Smoking and pregnancy: Epigenetics and developmental origins of the metabolic syndrome

Predictive Value of Homeostasis Model Assessment of Insulin Resistance, Visceral Fat Index, and Prepregnancy Body Mass Index in Gestational Metabolic Syndrome

OBJECTIVE

To explore the diagnostic value of homeostasis model assessment of insulin resistance (HOMA-IR), visceral fat index (VAI), and prepregnancy body mass index (BMI) in gestational metabolic syndrome (GMS).

METHODS

From December 2019 to March 2021,122 GMS high-risk pregnant women who received routine antenatal clinic visits and planned to give birth in our hospital were selected as the research objects. Pregnant women were divided into the GMS group (n = 79) and the control group (n = 43) according to GMS diagnostic criteria during the gestation period of 32-36 weeks. The general information such as age and gestational week of pregnant women as well as HOMA-IR, VAI, and BMI before pregnancy were compared between the two groups. The glucose and lipid metabolism indexes of pregnant women in two groups were analyzed, the detection rates of HOMA-IR, VAI, and prepregnancy BMI in GMS between the two groups were compared. Logistic regression was used to analyze the risk factors for GMS in pregnant women, and receiver operating characteristic curve (ROC) was used to analyze the diagnostic value of HOMA-IR, VAI, prepregnancy BMI, and the combination of the three for GMS.

RESULTS

The body weight, systolic blood pressure, and diastolic blood pressure of the GMS group were higher than those of the control group, and the differences were statistically significant (P < 0.05). There was no significant difference in age, gestational week, and height between the two groups (P > 0.05). The levels of FPG, FINS, TC, TG, LDL-C, and FFA in the GMS group were higher than the control group, the level of HDL-C in the GMS group was lower than the control group, and the difference was statistically significant (P < 0.05). The levels of HOMA-IR, VAI, and prepregnancy BMI in the GMS group were higher than those in the control group, and the differences were statistically significant (P < 0.05). The positive detection rates of HOMA-IR, VAI, and prepregnancy BMI in the GMS group were 83.54%, 86.07%, and 81.01%, respectively. There was no significant difference in the positive detection rates of HOMA-IR, VAI, and prepregnancy BMI between the two groups (P > 0.05). High levels of HOMA-IR, VAI, and prepregnancy BMI were risk factors for GMS in pregnant women (P < 0.05). ROC curve showed area under the curve for HOMA-IR was 0.810, area under the curve for VAI was 0.771, and area under the curve for prepregnancy BMI was 0.749. The AUC for the combination of HOMA-IR, VAI, and prepregnancy BMI was 0.918.

CONCLUSION

HOMA-IR, VAI, and prepregnancy BMI in GMS have a high detection rate and certain diagnostic value, and the combination of the three has higher clinical value.

Prenatal nicotine exposure was associated with long-term impact on the cardiovascular system and regulation-Review

AIM

The aim of this structured review was to discuss knowledge of nicotine use during pregnancy and long-term effects on children's cardiovascular function.

METHODS

PubMed and MEDLINE were searched for original papers that covered various forms of nicotine exposure during pregnancy and this identified 314 papers published in English from inception of the databases to 1 March 2021. The research focus was prenatal exposure that had long-term effects on the cardiovascular system. The search was expanded from the reference list of the selected papers, which identified another 17 papers.

RESULTS

The 34 original papers that were included covered 172,696 subjects from foetuses to 19 years of age. Cardiovascular autonomic dysfunction was discussed in 12 of the papers and 16 studies reported on blood pressure. The remaining studies covered structural or functional changes in arterial wall or heart. There were convincing data on autonomic dysfunction and increased blood pressure. Some data were conflicting and problems with misclassification of exposure were evident.

CONCLUSION

Prenatal nicotine exposure was associated with long-term developmental changes in the cardiovascular system and regulation. There were no safe periods, doses or nicotine products during pregnancy and women should abstain when planning a pregnancy.

Epigenetic Alterations of Maternal Tobacco Smoking during Pregnancy: A Narrative Review

In utero exposure to maternal tobacco smoking is the leading cause of birth complications in addition to being associated with later impairment in child’s development. Epigenetic alterations, such as DNA methylation (DNAm), miRNAs expression, and histone modifications, belong to possible underlying mechanisms linking maternal tobacco smoking during pregnancy and adverse birth outcomes and later child’s development. The aims of this review were to provide an update on (1) the main results of epidemiological studies on the impact of in utero exposure to maternal tobacco smoking on epigenetic mechanisms, and (2) the technical issues and methods used in such studies. In contrast with miRNA and histone modifications, DNAm has been the most extensively studied epigenetic mechanism with regard to in utero exposure to maternal tobacco smoking. Most studies relied on cord blood and children’s blood, but placenta is increasingly recognized as a powerful tool, especially for markers of pregnancy exposures. Some recent studies suggest reversibility in DNAm in certain genomic regions as well as memory of smoking exposure in DNAm in other regions, upon smoking cessation before or during pregnancy. Furthermore, reversibility could be more pronounced in miRNA expression compared to DNAm. Increasing evidence based on longitudinal data shows that maternal smoking-associated DNAm changes persist during childhood. In this review, we also discuss some issues related to cell heterogeneity as well as downstream statistical analyses used to relate maternal tobacco smoking during pregnancy and epigenetics. The epigenetic effects of maternal smoking during pregnancy have been among the most widely investigated in the epigenetic epidemiology field. However, there are still huge gaps to fill in, including on the impact on miRNA expression and histone modifications to get a better view of the whole epigenetic machinery. The consistency of maternal tobacco smoking effects across epigenetic marks and across tissues will also provide crucial information for future studies. Advancement in bioinformatic and biostatistics approaches is key to develop a comprehensive analysis of these biological systems.

Impact of nicotine and maternal BMI on fetal birth weight

BACKGROUND

According to the World Health Organization, smoking is the most important risk factor for adverse pregnancy outcomes in industrialized nations. As the individual factors (body mass index - BMI (kg/m2) - and cigarette consumption) have been extensively investigated in pregnancy, we aimed to establish how maternal BMI and nicotine interact with regard to perinatal outcomes and birth weight.

METHODS

Data from 110.047 singleton pregnancies, achieved from the German Perinatal Survey in Schleswig-Holstein and registered between 2010 and 2017 were analyzed in August 2018 concerning maternal BMI and smoking. The BMI was taken from the maternity log. Information concerning the smoking status were self-reported and further subdivided into the following four categories: a) non-smokers; b) 1-7 cigarettes/day; c) 8-14 cigarettes/ day; and d) ≥ 15 cigarettes/ day. Furthermore, we classified women by their BMI into underweight, normal weight, overweight and obese. Comparisons between non-smokers and the respective smoking group, and their relationship with maternal BMI were performed by the t-test (birth weight). A P-value ≤0.05 was considered to indicate statistical significance.

RESULTS

A number of 97.092 women (88.2%) were non-smokers and 12.955 (11.8%) were smokers. Furthermore 10.3% of women of normal weight smoked during pregnancy, but both high and low BMI were associated with a high prevalence of smoking. The proportion of smokers was highest (18.1%) among underweight women (BMI ≤ 18.5 kg/m2). A large number of smokers (15.5%) were registered in the obesity group (BMI ≥ 30 kg/m2). Mean birth weight (≥ 37 + 0 gestational age) increased with increasing maternal BMI, and was reduced by smoking for every BMI category. The differences between smokers and non-smokers were always highly significant (p < 0.001). Mean birth weight varied between 2995 g in underweight frequent smokers and 3607 g in obese non-smokers.

CONCLUSION

Both maternal BMI and smoking during pregnancy influences the birth weight and therefore pregnancy outcome. Smoking during pregnancy was significantly associated with low birth weight. Pregnant women should be advised to cease or at least reduce smoking in order to improve the birth weight of the newborn and to minimize child morbidities.

Obesity and endocrine-disrupting chemicals

Obesity is now a worldwide pandemic. The usual explanation given for the prevalence of obesity is that it results from consumption of a calorie dense diet coupled with physical inactivity. However, this model inadequately explains rising obesity in adults and in children over the past few decades, indicating that other factors must be important contributors. An endocrine-disrupting chemical (EDC) is an exogenous chemical, or mixture that interferes with any aspect of hormone action. EDCs have become pervasive in our environment, allowing humans to be exposed daily through ingestion, inhalation, and direct dermal contact. Exposure to EDCs has been causally linked with obesity in model organisms and associated with obesity occurrence in humans. Obesogens promote adipogenesis and obesity, in vivo, by a variety of mechanisms. The environmental obesogen model holds that exposure to obesogens elicits a predisposition to obesity and that such exposures may be an important yet overlooked factor in the obesity pandemic. Effects produced by EDCs and obesogen exposure may be passed to subsequent, unexposed generations. This "generational toxicology" is not currently factored into risk assessment by regulators but may be another important factor in the obesity pandemic as well as in the worldwide increases in the incidence of noncommunicable diseases that plague populations everywhere. This review addresses the current evidence on how obesogens affect body mass, discusses long-known chemicals that have been more recently identified as obesogens, and how the accumulated knowledge can help identify EDCs hazards.

Maternal nicotine exposure impairs brown adipose tissue via AMPK-SIRT1-PGC-1α signals in male offspring

AIMS

Maternal nicotine exposure during pregnancy and lactation is associated with obesity in offspring. Brown adipose tissue (BAT) is correlated with energy metabolism and obesity. In this study, we explored the mechanism of maternal nicotine exposure on BAT changes in male offspring.

MAIN METHODS

Pregnant rats were randomly assigned to nicotine (1.0 mg/kg twice per day, subcutaneous administration) or control groups. In vitro, C3H10T1/2 cells were induced to differentiate into mature brown adipocytes, and 0-50 μM nicotine was given to C3H10T1/2 cells during the differentiation process.

KEY FINDINGS

Nicotine-exposed males had white-like adipocytes and abnormal mitochondria structure in iBAT at 26 weeks. The expression of mitochondrial genes, UCP1 and AMPK-SIRT1-PGC-1α pathway were downregulated in the nicotine group at 26 weeks rather than 4 weeks. In vitro, 50 μM nicotine decreased the expression of mitochondrial genes, UCP1 and AMPK-SIRT1-PGC-1α pathway in brown adipocytes.

SIGNIFICANCE

Maternal nicotine exposure showed the "programming" effect on the decreased brown-like phenotype in BAT of adult male offspring via downregulating AMPK-SIRT1-PGC-1α pathway. This impairment of BAT may be a potential mechanism of nicotine-induced obesity in male offspring.

Pregestational BMI and higher offspring's risk of overweight/obesity in smoker and non-smoker mothers

OBJECTIVE

To assess the association between pregestational BMI and offspring's risk of overweight/obesity after accounting for the most important confounders, especially maternal smoking habit.

DESIGN

Prospective cohort study.

SETTING

The Seguimiento Universidad de Navarra (SUN) study is a prospective cohort of Spanish graduates with more than 22 000 participants nationwide. Recruitment started in 1999, and it is permanently open. Data on diet, lifestyle and clinical diagnoses are collected at baseline and every 2 years.

PARTICIPANTS

Women from the SUN cohort who reported at least one pregnancy during follow-up (n 3496) were invited to this study. Among them, 1527 agreed to participate and completed an additional more detailed online questionnaire on their pregnancy history and their offspring's nutritional status.

RESULTS

After excluding 165 children, we analysed data of 2791 participants born to 1485 mothers and observed that each 5 kg/m2 increase in pregestational BMI was associated with a 0·22 (95 % CI 0·15, 0·29) higher z-score in offspring's BMI and higher risk of overweight/obesity (multivariable-adjusted relative risk (RR) 1·57 (95 % CI 1·39, 1·77)) in childhood or adolescence. Furthermore, we observed stronger association in children born to smoker mothers (RR 1·91; 95 % CI 1·48, 2·46) than from non-smoker mothers (RR 1·51; 95 % CI 1·31, 1·73) (Pfor interaction = 0·02).

CONCLUSIONS

We found a synergistic interaction between pregestational BMI and maternal smoking habit on offspring's z-score of the BMI and in their risk of overweight/obesity. Although further research is needed to analyse dose-response relationships, these findings reinforce the importance of promoting healthy lifestyles in pregnant women in order to prevent childhood obesity.

Early Life Exposure to Nicotine: Postnatal Metabolic, Neurobehavioral and Respiratory Outcomes and the Development of Childhood Cancers

Cigarette smoking during pregnancy is associated with numerous obstetrical, fetal, and developmental complications, as well as an increased risk of adverse health consequences in the adult offspring. Nicotine replacement therapy and electronic nicotine delivery systems (e-cigarettes) have been developed as a pharmacotherapy for smoking cessation and are considered safer alternatives for women to smoke during pregnancy. The safety of nicotine replacement therapy use during pregnancy has been evaluated in a limited number of short-term human trials, but there is currently no information on the long-term effects of developmental nicotine exposure in humans. However, animal studies suggest that nicotine alone may be a key chemical responsible for many of the long-term effects associated with maternal cigarette smoking on the offspring and increases the risk of adverse neurobehavioral outcomes, dysmetabolism, respiratory illness, and cancer. This review will examine the long-term effects of fetal and neonatal nicotine exposure on postnatal health.

Smoking and Smoking Cessation in the Risk for Fetal Growth Restriction and Low Birth Weight and Additive Effect of Maternal Obesity

Many studies have shown that neonates of smoking mothers have a lower birth weight, but several issues remain poorly studied, e.g., the effects of giving up smoking or the combined effects of smoking and maternal obesity. Therefore, we evaluated a prospective cohort of 912 mothers in a single pregnancy, recruited in Poland, in 2015−2016. In the cohort, we recorded 72 (7.9%) newborns with birth weight <10th percentile, 21 (2.3%) fetal growth restriction (FGR) cases, and 60 (6.6%) low birth weight (LBW, <2500 g) newborns. In the cohort, 168 (18.4%) women smoked before pregnancy; the mean number of cigarettes/day was 10.8 (1–30), and the mean number of years of cigarette smoking was 8.5 (1–25). Among smokers, 57 (6.3%) women smoked in the first trimester. Adjusted odds ratio (AOR) of newborn outcomes (with 95% confidence intervals, CI) was calculated in multi-dimensional logistic regressions. Compared to participants who had never smoked, smoking before pregnancy was associated with a higher odds ratio of birth weight <10th percentile (AOR = 1.93, CI: 1.08–3.44, p = 0.027), but the result for LBW (AOR = 2.76, CI: 1.05–7.26, p = 0.039) and FGR (AOR = 1.13, CI: 0.38–3.36, p = 0.822) had the wider confidence interval or was insignificant. Effects of smoking cessation before pregnancy were statistically insignificant for the studied outcomes. Smoking in the first trimester was associated with a higher risk of birth weight <10th percentile (AOR = 4.68, CI: 2.28–9.62, p < 0.001), LBW (AOR = 6.42, CI: 1.84–22.36, p = 0.004), and FGR (AOR = 3.60, CI: 0.96–13.49, p = 0.057). Smoking cessation in the second/third trimester was associated with a higher odds ratio of birth weight <10th percentile (AOR = 4.54, CI: 1.58–13.02, p = 0.005), FGR (AOR = 3.36, CI: 0.6–18.74, p = 0.167), and LBW (AOR = 2.14, CI: 0.62–7.36), p = 0.229), to a similar degree to smoking in the first trimester. The odds ratios were higher in the subgroup of pre-pregnancy body mass index ≥25 kg/m² for the risk of birth weight <10th percentile (AOR = 6.39, CI: 2.01–20.34, p = 0.002) and FGR (AOR = 6.25, CI: 0.86–45.59, p = 0.071). The length of cigarette smoking time was also the risk factor for studied outcomes. Conclusions: Smoking in the first trimester increased the studied risks, and the coexistence of excessive maternal weight increased the effects. Smoking cessation during the second/third trimester did not have a protective effect.

Thyroid redox imbalance in adult Wistar rats that were exposed to nicotine during breastfeeding

Maternal nicotine exposure causes several consequences in offspring phenotype, such as obesity and thyroid dysfunctions. Nicotine exposure can increase oxidative stress levels, which could lead to thyroid dysfunction. However, the mechanism by which nicotine exposure during breastfeeding leads to thyroid gland dysfunction remains elusive. We aimed to investigate the long-term effects of maternal nicotine exposure on redox homeostasis in thyroid gland, besides other essential steps for thyroid hormone synthesis in rats from both sexes. Lactating Wistar rats were implanted with osmotic minipumps releasing nicotine (NIC, 6 mg/kg/day) or saline (control) from postnatal day 2 to 16. Offspring were analyzed at 180-day-old. NIC males showed lower plasma TSH, T₃ and T₄ while NIC females had higher T₃ and T₄. In thyroid, NIC males had higher sodium-iodide symporter protein expression, whereas NIC females had higher thyroid-stimulating hormone receptor (TSHr) and thyroperoxidase (TPO) protein expression. TPO activity was lower in NIC males. Hydrogen peroxide generation was decreased in NIC males. Activities of superoxide dismutase, catalase and glutathione peroxidase were compromised in NIC animals from both sexes. 4-Hydroxynonenal was higher only in NIC females, while thiol was not affected in NIC animals from both sexes. NIC offspring also had altered expression of sex steroid receptors in thyroid gland. Both sexes showed similar thyroid morphology, with lower follicle and colloid size. Thyroid from female offspring exposed to nicotine during breastfeeding developed oxidative stress, while the male gland seemed to be protected from redox damage. Thyroid dysfunctions seem to be associated with redox imbalance in a sex-dependent manner.

Global epigenetic alterations of mesenchymal stem cells in obesity: the role of vitamin C reprogramming

Obesity promotes dysfunction and impairs the reparative capacity of mesenchymal stem/stromal cells (MSCs), and alters their transcription, protein content, and paracrine function. Whether these adverse effects are mediated by chromatin-modifying epigenetic changes remains unclear. We tested the hypothesis that obesity imposes global DNA hydroxymethylation and histone tri-methylation alterations in obese swine abdominal adipose tissue-derived MSCs compared to lean pig MSCs. MSCs from female lean (n = 7) and high-fat-diet fed obese (n = 7) domestic pigs were assessed using global epigenetic assays, before and after in-vitro co-incubation with the epigenetic modulator vitamin-C (VIT-C) (50 μg/ml). Dot blotting was used to measure across the whole genome 5-hydroxyemthycytosine (5hmC) residues, and Western blotting to quantify in genomic histone-3 protein tri-methylated lysine-4 (H3K4me3), lysine-9 (H3K9me3), and lysine-27 (H3K27me3) residues. MSC migration and proliferation were studied in-vitro. Obese MSCs displayed reduced global 5hmC and H3K4m3 levels, but comparable H3K9me3 and H3K27me3, compared to lean MSCs. Global 5hmC, H3K4me3, and HK9me3 marks correlated with MSC migration and reduced proliferation, as well as clinical and metabolic characteristics of obesity. Co-incubation of obese MSCs with VIT-C enhanced 5hmC marks, and reduced their global levels of H3K9me3 and H3K27me3. Contrarily, VIT-C did not affect 5hmC, and decreased H3K4me3 in lean MSCs. Obesity induces global genomic epigenetic alterations in swine MSCs, involving primarily genomic transcriptional repression, which are associated with MSC function and clinical features of obesity. Some of these alterations might be reversible using the epigenetic modulator VIT-C, suggesting epigenetic modifications as therapeutic targets in obesity.

Associations between Maternal and Fetal Levels of Total Adiponectin, High Molecular Weight Adiponectin, Selected Somatomedins, and Birth Weight of Infants of Smoking and Non-Smoking Mothers

The aim of the study was to determine the relationships between maternal smoking, total adiponectin, high molecular weight adiponectin (HMW adiponectin), selected somatomedins, and the birth weight of newborns. A total of 78 women with a healthy, singleton pregnancy, 41 active smokers and 37 non-smokers, and their offspring were studied. Total and HMW adiponectin, insulin-like growth factor I (IGF-I), and insulin-like growth factor binding protein-1 (IGFBP-1) and 2 (IGFBP-2) were determined in maternal and cord blood by enzyme-link immunosorbent assay. Serum levels of total and HMW adiponectin were lower in smokers compared to the tobacco abstinent in both the mothers (p = 0.013; p = 0.006) and the infants (p = 0.001; p = 0.047). In smoking women and their children, serum concentrations of IGF-I were significantly lower (p = 0.014; p = 0.042), IGFBP-1 significantly higher (p = 0.009; p = 0.039), and IGFBP-2 did not differ from that observed in the non-smoking group. In multivariate analysis performed on the whole group of mothers, the highest impact of serum cotinine and IGFBP-2 levels were indicated for adiponectin and cotinine and the number of cigarettes/day for HMW adiponectin concentration. In correlation analysis estimated separately for smokers and non-smokers, neonatal birth weight was positively associated with total and HMW adiponectin concentrations in umbilical cord blood. Birth weight was also inversely associated with IGFBP-1 and positively correlated with IGF-I levels in maternal serum as well as in cord blood (r = −0.317, p = 0.005; r = −0.294, p = 0.004; r = 0.245, p = 0.031; r = 0.271, p = 0.009, respectively). The present study showed the levels of total and HMW adiponectin in umbilical cord blood may have a significant effect on fetal development. Both IGF-I and IGFBP-1 concentrations also play an essential role in fetal growth, which is an important predictor of birth weight. Cigarette smoking during pregnancy negatively affected adiponectin and the insulin growth factor profile in the serum of women and the cord blood and may be the reason for the lower birth weight of the smokers newborns compared with the nonsmokers offspring.

Maternal overnutrition impairs offspring's insulin sensitivity: A systematic review and meta-analysis

This systematic review and meta‐analysis aimed to investigate the association between maternal overnutrition and offspring's insulin sensitivity—following the Preferred Reporting Items for Systematic Reviews and Meta‐analyses statement. Studies published in English before April 22, 2019, were identified through searches of four medical databases. After selection, 15 studies aiming to explore the association between prepregnancy body mass index (ppBMI) or gestational weight gain (GWG) of non‐diabetic mothers and their offspring's insulin sensitivity (fasting insulin or glucose level and Homeostatic Measurement Assessment for Insulin Resistance [HOMA‐IR]) were included in the meta‐analysis. Associations of ppBMI and GWG with offspring's insulin sensitivity were analysed by pooling regression coefficients or standardized differences in means with 95% confidence intervals (CIs). Maternal ppBMI showed significant positive correlations with the level of both fasting insulin and HOMA‐IR in offspring (standardized regression coefficient for fasting insulin: 0.107, CI [0.053, 0.160], p < 0.001 and that for HOMA‐IR: 0.063, CI [0.006, 0.121], p = 0.031). However, the result of the analysis on coefficients adjusted for offspring's actual anthropometry (BMI and adiposity) was not significant. Independent from ppBMI, GWG tended to show a positive correlation with insulin level, but not after adjustment for offspring's anthropometry. Offspring of mothers with excessive GWG showed significantly higher HOMA‐IR than those of mothers with optimal GWG (p = 0.004). Our results demonstrate that both higher ppBMI and GWG increase the risk of offspring's insulin resistance, but the effect of ppBMI on insulin sensitivity in offspring may develop as consequence of their adiposity.

Prevalence of the number of pre-gestational diagnoses and trends in the United States in 2006 and 2016

Introduction: There is a trend in reproductive-aged women to live with more chronic conditions, likely resulting in pregnancies complicated by one or more pre-gestational diagnoses. The objective of this study is to determine the prevalence of women with pre-gestational diagnoses and pregnancy-related complications, and assess the trends of pre-gestational diagnoses between two time-points, ten-years apart from 2006 to 2016.Materials and methods: We abstracted pregnant patients from the Healthcare Cost and Utilization Project's National Inpatient Sample by the Agency for Healthcare Research and Quality in 2006 and 2016. We classified diagnosis codes, ICD 9 for 2006 and ICD 10 for 2016, as pre-gestational diagnoses or as pregnancy-related complications. Descriptive statistics were presented as frequencies and proportions for categorical variables. Chi-square analysis was performed. All statistical analyses were two-sided and p-value < .05 was considered to be statistically significant.Results: Between 2006 and 2016, the percentage of patients with at least one pre-gestational diagnoses increased from 35.3% in 2006 to 53.8% in 2016 (p < .0001) and the percentage of patients with at least one pregnancy-related complication increased from 62.6% to 69.1% (p < .0001). We found a trend of increasing pregnancy-related complications with an increasing number of pre-gestational diagnoses. The prevalence of asthma and obesity, either alone or in combination were found to rise over the ten-year time span.Conclusion: The percent of patients entering pregnancy with any pre-gestational diagnosis has increased, along with the number of pregnancy-related complications. Future research is needed to understand the effects of these diagnoses in combination and the possible impact on pregnancy outcomes.

Prenatal exposure to traffic and ambient air pollution and infant weight and adiposity: The Healthy Start study

BACKGROUND

Prenatal exposures to ambient air pollution and traffic have been associated with adverse birth outcomes, and may also lead to an increased risk of obesity. Obesity risk may be reflected in changes in body composition in infancy.

OBJECTIVE

To estimate associations between prenatal ambient air pollution and traffic exposure, and infant weight and adiposity in a Colorado-based prospective cohort study.

METHODS

Participants were 1125 mother-infant pairs with term births. Birth weight was recorded from medical records and body composition measures (fat mass, fat-free mass, and adiposity [percent fat mass]) were evaluated via air displacement plethysmography at birth (n = 951) and at ~5 months (n = 574). Maternal residential address was used to calculate distance to nearest roadway, traffic density, and ambient concentrations of fine particulate matter (PM_2.5) and ozone (O₃) via inverse-distance weighted interpolation of stationary monitoring data, averaged by trimester and throughout pregnancy. Adjusted linear regression models estimated associations between exposures and infant weight and body composition.

RESULTS

Participants were urban residents and diverse in race/ethnicity and socioeconomic status. Average ambient air pollutant concentrations were generally low; the median, interquartile range (IQR), and range of third trimester concentrations were 7.3 μg/m³ (IQR: 1.3, range: 3.3-12.7) for PM_2.5 and 46.3 ppb (IQR: 18.4, range: 21.7-63.2) for 8-h maximum O_3. Overall there were few associations between traffic and air pollution exposures and infant outcomes. Third trimester O₃ was associated with greater adiposity at follow-up (2.2% per IQR, 95% CI 0.1, 4.3), and with greater rates of change in fat mass (1.8 g/day, 95% CI 0.5, 3.2) and adiposity (2.1%/100 days, 95% CI 0.4, 3.7) from birth to follow-up.

CONCLUSIONS

We found limited evidence of an association between prenatal traffic and ambient air pollution exposure and infant body composition. Suggestive associations between prenatal ozone exposure and early postnatal changes in body composition merit further investigation.

Determinants of Maternal Insulin Resistance during Pregnancy: An Updated Overview

Insulin resistance changes over time during pregnancy, and in the last half of the pregnancy, insulin resistance increases considerably and can become severe, especially in women with gestational diabetes and type 2 diabetes. Numerous factors such as placental hormones, obesity, inactivity, an unhealthy diet, and genetic and epigenetic contributions influence insulin resistance in pregnancy, but the causal mechanisms are complex and still not completely elucidated. In this review, we strive to give an overview of the many components that have been ascribed to contribute to the insulin resistance in pregnancy. Knowledge about the causes and consequences of insulin resistance is of extreme importance in order to establish the best possible treatment during pregnancy as severe insulin resistance can result in metabolic dysfunction in both mother and offspring on a short as well as long-term basis.