Maternal smoking during pregnancy, fetal arterial resistance adaptations and cardiovascular function in childhood

Vitamin C supplementation improves placental function and alters placental gene expression in smokers

Maternal smoking during pregnancy (MSDP), driven by nicotine crossing the placenta, causes lifelong decreases in offspring pulmonary function and vitamin C supplementation during pregnancy prevents some of those changes. We have also shown in animal models of prenatal nicotine exposure that vitamin C supplementation during pregnancy improves placental function. In this study we examined whether vitamin C supplementation mitigates the effects of MSDP on placental structure, function, and gene expression in pregnant human smokers. Doppler ultrasound was performed in a subset of 55 pregnant smokers participating in the "Vitamin C to Decrease the Effects of Smoking in Pregnancy on Infant Lung Function" (VCSIP) randomized clinical trial (NCT01723696) and in 33 pregnant nonsmokers. Doppler ultrasound measurements showed decreased umbilical vein Doppler velocity (Vmax) in placebo-treated smokers that was significantly improved in smokers randomized to vitamin C, restoring to levels comparable to nonsmokers. RNA-sequencing demonstrated that vitamin C supplementation to pregnant smokers was associated with changes in mRNA expression in genes highly relevant to vascular and cardiac development, suggesting a potential mechanism for vitamin C supplementation in pregnant smokers to improve some aspects of offspring health.

Association of magnesium deficiency, tobacco smoke exposure and hypertension in children and adolescents: evidence from the NHANES 2007-2018

BACKGROUND

Recent studies suggested that the combination of tobacco smoke exposure (TSE) and dietary nutrients intake may be related to a higher or lower risk of hypertension. However, the relationship between dietary magnesium (Mg) intake, TSE and the odds of hypertension remain unclear. This study aimed to evaluate the association of TSE, dietary Mg intake and the odds of hypertension among children and adolescents.

METHOD

Data of this study were extracted from the National Health and Nutrition Examination Surveys (NHANES) 2007-2018. Dietary Mg intake was calculated as the average of two days of dietary and supplementations intake. Serum cotinine concertation ≥ 0.05 µg/L or at least one-person smoking in the household was considered as exposing to the tobacco smoke. The weighted univariate and multivariate logistic regression models were utilized to explore the associations of dietary Mg intake, TSE and the odds of hypertension among children and adolescents with the evaluation index of odds ratio (ORs) and 95% confidence intervals (CIs). Subgroup analyses based on different age, gender and overweight were further assessed these associations.

RESULTS

A total of 7,122 children and adolescents aged 8-17 years old and with the blood pressure measurement were included. Of which, 948 (13.31%) had hypertension. After adjusting all covariates, we observed children and adolescents exposed to tobacco smoke was related to higher odds of hypertension (OR = 1.34, 95%CI: 1.01-1.78); children and adolescents not reached the dietary Mg references intakes was related to higher odds of hypertension (OR = 1.48, (95%CI: 1.11-1.97); compared to children and adolescents non-TSE and reached the DRIs of Mg, those not reached the DRIs of Mg and exposed to tobacco smoke have the highest odds of hypertension (OR = 1.94, 95%CI: 1.30-2.89, P for trend = 0.002). These associations of dietary Mg intake, TSE and hypertension remain robust after the stratified analysis based on age, gender and overweight was conducted.

CONCLUSION

Our findings suggested there were a robust association between dietary Mg intake, TSE and hypertension in children and adolescents. Those children and adolescents with deficiency dietary Mg intake and exposed to tobacco smoke may have the high odds of hypertension. More restrictions on smoking as well as Mg supplementation in the prevention and treatment of hypertension among children and adolescents might be justified.

Involuntary tobacco smoke exposures from conception to 18 years increase midlife cardiometabolic disease risk: a 40-year longitudinal study

Few population studies have sufficient follow-up period to examine early-life exposures with later life diseases. A critical question is whether involuntary exposure to tobacco smoke from conception to adulthood increases the risk of cardiometabolic diseases (CMD) in midlife. In the Collaborative Perinatal Project, serum-validated maternal smoking during pregnancy (MSP) was assessed in the 1960s. At a mean age of 39 years, 1623 offspring were followed-up for the age at first physician-diagnoses of any CMDs, including diabetes, heart disease, hypertension, or hyperlipidemia. Detailed information on their exposure to environmental tobacco smoke (ETS) in childhood and adolescence was collected with a validated questionnaire. Cox regression was used to examine associations of in utero exposure to MSP and exposure to ETS from birth to 18 years with lifetime incidence of CMD, adjusting for potential confounders. We calculated midlife cumulative incidences of hyperlipidemia (25.2%), hypertension (14.9%), diabetes (3.9%), and heart disease (1.5%). Lifetime risk of hypertension increased by the 2nd -trimester exposure to MSP (adjusted hazard ratio: 1.29, 95% confidence interval: 1.01-1.65), ETS in childhood (1.11, 0.99-1.23) and adolescence (1.22, 1.04-1.44). Lifetime risk of diabetes increased by joint exposures to MSP and ETS in childhood (1.23, 1.01-1.50) or adolescence (1.47, 1.02-2.10). These associations were stronger in males than females, in never-daily smokers than lifetime ever smokers. In conclusion, early-life involuntary exposure to tobacco smoke increases midlife risk of hypertension and diabetes in midlife.

Cardiovascular Risk in Pediatrics: A Dynamic Process during the First 1000 Days of Life

The early childhood period, encompassing prenatal and early stages, assumes a pivotal role in shaping cardiovascular risk factors. We conducted a narrative review, presenting a non-systematic summation and analysis of the available literature, focusing on cardiovascular risk from prenatal development to the first 1000 days of life. Elements such as maternal health, genetic predisposition, inadequate fetal nutrition, and rapid postnatal growth contribute to this risk. Specifically, maternal obesity and antibiotic use during pregnancy can influence transgenerational risk factors. Conditions at birth, such as fetal growth restriction and low birth weight, set the stage for potential cardiovascular challenges. To consider cardiovascular risk in early childhood as a dynamic process is useful when adopting a personalized prevention for future healthcare and providing recommendations for management throughout their journey from infancy to early adulthood. A comprehensive approach is paramount in addressing early childhood cardiovascular risks. By targeting critical periods and implementing preventive strategies, healthcare professionals and policymakers can pave the way for improved cardiovascular outcomes. Investing in children's health during their early years holds the key to alleviating the burden of cardiovascular diseases for future generations.

Associations between prenatal alcohol and tobacco exposure on Doppler flow velocity waveforms in pregnancy: a South African study

BACKGROUND

The negative impact of prenatal alcohol and tobacco exposure (PAE and PTE) on fetal development and birth outcomes are well described, yet pathophysiologic mechanisms are less clear. Our aim was to investigate (1) the associations between quantity, frequency and timing (QFT) of PAE and PTE with blood flow velocities in arteries of the fetal-placental-maternal circulation and (2) the extent to which combined effect of QFT of PAE and/or PTE and Doppler flow velocity waveforms (FWV) predict infant birth weight.

METHODS

The Safe Passage Study is a cohort based in urban Cape Town, South Africa. Recruitment occurred between 2007 and 2015. Information on QFT of PAE and PTE was collected prospectively at up to 4 occasions during pregnancy using a modified Timeline Follow-Back approach. Ultrasound examinations consisted of Doppler flow velocity waveforms of the uterine, umbilical (UA) and fetal middle cerebral arteries for the pulsatility index (PI) at 20-24 and 34-38 weeks. Exclusion criteria included: twin pregnancies, stillbirths, participants exposed to other drugs. The sample was divided into three groups (controls, PAE and PTE) and included 1396 maternal-fetal-dyads assessed during the second trimester; 1398 assessed during the third trimester.

RESULTS

PTE was associated with higher UA PI values in second and third trimesters (p < 0.001), compared to the PAE and control group. The total amount of cigarettes smoked during pregnancy was positively correlated with UA PI values (r = 0.087, p < 0.001). There was a positive correlation between cigarettes smoked per day in trimester one (r = 0.091, p < 0.01), and trimester two (r = 0.075, p < 0.01) and UA PI (in trimester two), as well as cigarettes smoked per day in trimester two (r = 0.058, p < 0.05) and trimester three (r = 0.069, p < 0.05) and the UA PI in trimester three. Generalized additive models indicated that PAE in trimester two, PTE in trimester one and Doppler FWV in trimester three were significant predictors of birth weight in this sample.

CONCLUSION

In our study, PTE in trimesters two and three resulted in increased vascular resistance of the placenta. These findings highlight nuance in associations between PAE, PTE and blood flow velocities in arteries of the fetal-placental-maternal circulation and birth weight, suggesting that quantity and timing are important factors in these relationships.

Vascular Effects, Potential Pathways and Mediators of Fetal Exposure to Alcohol and Cigarette Smoking during Pregnancy: A Narrative Review

(1) Background: Programming of atherosclerosis results in vascular structure and function alterations, which may be attributed to fetal exposure to maternal tobacco smoking, alcohol consumption and several lifestyle factors in the first few years of life. This review aims to study the effects of teratogen exposure in utero on vascular dysfunction in offspring and consider mediators and pathways originating from the fetal environment. (2) Methods: Eligible studies were identified in the PubMed, Scopus and Web of Science databases. After the full-text screening, 20 articles were included in the narrative synthesis. (3) Results: The literature presents evidence supporting the detrimental effects of fetal exposure to tobacco smoking on vascular alterations in both human and animal studies. Alcohol exposure impaired endothelial dilation in animal studies, but human studies on both tobacco and alcohol exposure are still sparse. Reduction in nitric oxide (NO) bioavailability and alterations in the epigenome in infants through the upregulation of pro-oxidative and proinflammatory genes may be the common denominators. (4) Conclusion: While maternal smoking and alcohol consumption have more negative outcomes on the infant in the short term, several factors during the first few years of life may mediate the development of vascular dysfunction. Therefore, more prospective studies are needed to ascertain the long-term effects of teratogen exposure, specifically in South Africa.

Fetal Exposure to Maternal Smoking and Neonatal Metabolite Profiles

Fetal tobacco exposure has persistent effects on growth and metabolism. The underlying mechanisms of these relationships are yet unknown. We investigated the associations of fetal exposure to maternal smoking with neonatal metabolite profiles. In a population-based cohort study among 828 mother-infant pairs, we assessed maternal tobacco use by questionnaire. Metabolite concentrations of amino acids, non-esterified fatty acids, phospholipids and carnitines were determined by using LC-MS/MS in cord blood samples. Metabolite ratios reflecting metabolic pathways were computed. Compared to non-exposed neonates, those exposed to first trimester only tobacco smoking had lower neonatal mono-unsaturated acyl-alkyl-phosphatidylcholines (PC.ae) and alkyl-lysophosphatidylcholines (Lyso.PC.e) 18:0 concentrations. Neonates exposed to continued tobacco smoking during pregnancy had lower neonatal mono-unsaturated acyl-lysophosphatidylcholines (Lyso.PC.a), Lyso.PC.e.16:0 and Lyso.PC.e.18:1 concentration (False discovery rate (FDR) p-values < 0.05). Dose-response associations showed the strongest effect estimates in neonates whose mothers continued smoking ≥5 cigarettes per day (FDR p-values < 0.05). Furthermore, smoking during the first trimester only was associated with altered neonatal metabolite ratios involved in the Krebs cycle and oxidative stress, whereas continued smoking during pregnancy was associated with inflammatory, transsulfuration, and insulin resistance markers (p-value < 0.05). Thus, fetal tobacco exposure seems associated with neonatal metabolite profile adaptations. Whether these changes relate to later life metabolic health should be studied further.

Maternal Factors in Pregnancy and Ethnicity Influence Childhood Adiposity, Cardiac Structure, and Function

IMPORTANCE

The links between maternal and offspring adiposity and metabolic status are well established. There is much less evidence for the impact of these relationships combined with ethnic background on cardiac structure and function in childhood.

OBJECTIVE

To test the hypothesis that ethnicity, maternal adiposity and glycemic status, and child adiposity affect cardiac structure and function.

DESIGN

A prospective cohort study.

SETTING

A single-center mother-child cohort study. The cohort is a subset of the international multi-center Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) study.

PARTICIPANTS

This study included 101 healthy pre-pubertal British-born children [56 White Europeans (WEs) and 45 South Asians (SAs)] with a median age of 9.1 years, range 6.0-12.2 years, at the time of the investigation.

MAIN OUTCOMES AND MEASURES

Anthropometric and echocardiographic measurements were made on the cohort. Maternal pregnancy and birth data were available. Relationships between maternal parameters (BMI and glucose status), child adiposity, and echo measures were assessed.

RESULTS

Despite no ethnic difference in BMI SDS at a median age of 9.1 years, SA children exhibited higher levels of body fat than WE children (whole body, right arm, and truncal fat all p < 0.001). SA children also exhibited greater changes in weight and height SDS but not BMI SDS from birth than WE children. As expected, maternal BMI correlated with child BMI (r = 0.28; p = 0.006), and body fat measures (e.g., whole body fat r = 0.25; p = 0.03). Maternal fasting glucose levels were associated with child body fat measures (r = 0.22-0.28; p = 0.02-0.05). Left ventricular (LV) indices were not different between SA and WE children, but E/A and E'/A' (measures of diastolic function) were lower in SA when compared with WE children. LV indices correlated positively to BMI SDS and body fat markers only in SA children. Maternal fasting and 2-h glucose were negatively correlated with E'/A' in SA children (r = -0.53, p = 0.015, and r = -0.49, p = 0.023, respectively) but not in WE children.

CONCLUSION AND RELEVANCE

SA and WE children exhibit differences in adiposity and diastolic function at a median age of 9.1 years. Novel relationships between maternal glycemia, child adiposity, and cardiac structure and function, present only in SA children, were identified.

Evaluation of Plasma Asymmetric Dimethylarginine Levels and Abdominal Aortic Intima-Media Thickness in Infants of Smoker Mothers

OBJECTIVE

Smoking during pregnancy has harmful effects on the fetus and infant. Although some studies suggest that exposure to fetal-maternal smoking adversely affects both fetal growth and cardiovascular development, the mechanisms and biochemical consequences of smoking in pregnancy and newborns are not yet fully understood. We aimed to investigate whether maternal smoking during pregnancy causes fetal cardiovascular effect by measuring serum asymmetric dimethylarginine (ADMA) level and abdominal aortic intima-media thickness (aIMT).

STUDY DESIGN

This prospective study was conducted in newborns of smoking mothers and never-smoker control mothers during their pregnancies. The babies were evaluated echocardiographically on the first day following birth. In two-dimensional mode, abdominal aIMT measurements were performed. ADMA was measured in umbilical cord blood at birth.

RESULTS

There were 25 mothers in the study group and 25 mothers in the control group. Serum ADMA levels were 0.459 ± 0.119 μmol/L in the study group and 0.374 ± 0.1127 μmol/L in the control group (p = 0.034). The aIMT value in the study group was 0.84 ± 0.026 mm and the aIMT value in the control group was 0.63 ± 0.011 mm (p = 0.005).

CONCLUSION

We found that both the serum ADMA and the aIMT significantly increased in the group with newborns of smoker mothers compared with the group of the newborns of never-smoker mothers. It may also be suggested that exposure to fetal-maternal smoking adversely affects cardiovascular development.

KEY POINTS

· It is a known fact that smoking during pregnancy has harmful effects on the development of the fetus and infant.. · We found that both the serum ADMA and aIMT were significantly higher in the group of infants of smoker mothers..

Impact of vitamin C supplementation on placental DNA methylation changes related to maternal smoking: association with gene expression and respiratory outcomes

BACKGROUND

Maternal smoking during pregnancy (MSDP) affects development of multiple organ systems including the placenta, lung, brain, and vasculature. In particular, children exposed to MSDP show lifelong deficits in pulmonary function and increased risk of asthma and wheeze. Our laboratory has previously shown that vitamin C supplementation during pregnancy prevents some of the adverse effects of MSDP on offspring respiratory outcomes. Epigenetic modifications, including DNA methylation (DNAm), are a likely link between in utero exposures and adverse health outcomes, and MSDP has previously been associated with DNAm changes in blood, placenta, and buccal epithelium. Analysis of placental DNAm may reveal critical targets of MSDP and vitamin C relevant to respiratory health outcomes.

RESULTS

DNAm was measured in placentas obtained from 72 smokers enrolled in the VCSIP RCT: NCT03203603 (37 supplemented with vitamin C, 35 with placebo) and 24 never-smokers for reference. Methylation at one CpG, cg20790161, reached Bonferroni significance and was hypomethylated in vitamin C supplemented smokers versus placebo. Analysis of spatially related CpGs identified 93 candidate differentially methylated regions (DMRs) between treatment groups, including loci known to be associated with lung function, oxidative stress, fetal development and growth, and angiogenesis. Overlap of nominally significant differentially methylated CpGs (DMCs) in never-smokers versus placebo with nominally significant DMCs in vitamin C versus placebo identified 9059 candidate "restored CpGs" for association with placental transcript expression and respiratory outcomes. Methylation at 274 restored candidate CpG sites was associated with expression of 259 genes (FDR < 0.05). We further identified candidate CpGs associated with infant lung function (34 CpGs) and composite wheeze (1 CpG) at 12 months of age (FDR < 0.05). Increased methylation in the DIP2C, APOH/PRKCA, and additional candidate gene regions was associated with improved lung function and decreased wheeze in offspring of vitamin C-treated smokers.

CONCLUSIONS

Vitamin C supplementation to pregnant smokers ameliorates changes associated with maternal smoking in placental DNA methylation and gene expression in pathways potentially linked to improved placental function and offspring respiratory health. Further work is necessary to validate candidate loci and elucidate the causal pathway between placental methylation changes and outcomes of offspring exposed to MSDP. Clinical trial registration ClinicalTrials.gov, NCT01723696. Registered November 6, 2012. https://clinicaltrials.gov/ct2/show/record/NCT01723696 .

Associations between respiratory and vascular function in early childhood

BACKGROUND AND OBJECTIVE

The link between respiratory and vascular health is well documented in adult populations. Impaired lung function is consistently associated with thicker arteries and higher incidence of cardiovascular disease. However, there are limited data on this relationship in young children and the studies that exist have focussed on populations at high risk of cardiorespiratory morbidity. We determined if an association exists between respiratory and cardiovascular function in young children and, if so, whether it is confounded by known cardiorespiratory risk factors.

METHODS

Respiratory and vascular data from a prospective cohort study established to evaluate the health implications 3 years after coal mine fire smoke exposure in children aged 3-5 years were used. Respiratory function was measured using the forced oscillation technique and included resistance at 5 Hz (R₅ ), reactance at 5 Hz (X₅ ) and area under the reactance curve (AX). Vascular health was measured by carotid intima-media thickness (ultrasound) and pulse wave velocity (arterial tonometry). Regression analyses were used to examine the relationship between the respiratory Z-scores and cardiovascular measures. Subsequent analyses were adjusted for potential confounding by maternal smoking during pregnancy, maternal education and exposure to fine particulate matter <2.5 μm in aerodynamic diameter (PM_2.5 ).

RESULTS

Peripheral lung function (X₅ and AX), but not respiratory system resistance (R₅ ), was associated with vascular function. Adjustment for maternal smoking, maternal education and early life exposure to PM_2.5 had minimal effect on these associations.

CONCLUSION

These observations suggest that peripheral lung stiffness is associated with vascular stiffness and that this relationship is established early in life.

In utero and postnatal exposure to environmental tobacco smoke, blood pressure, and hypertension in children: the Seven Northeastern Cities study

To evaluate the association of environmental tobacco smoke (ETS) exposure with hypertension and blood pressure (BP) in children, a sample of 9,354 children, aged 5-17 years, was studied from seven northeastern cities of China in 2012-2013. The results showesd that significant associations were observed for hypertension with ETS exposure in utero [odds ratio (OR) 1.36, 95% confidence interval (CI) 1.18-1.57], with current major ETS exposure from fathers (1.38, 1.21-1.57) or anyone (1.26, 1.12-1.42), and with intensity of ETS exposure greater than 1 cigarette per day (ORs ranged from 1.20 to 1.35). For SBP, significant associations were only observed in children with major ETS exposure from father and with cigarettes smoking >10/day. When stratified by sex, more significant associations were found in girls than in boys. In conclusion, prenatal and postnatal ETS exposure was significantly associated with increased odds of hypertension in children, especially in girls.

Early life exposure to coal mine fire and tobacco smoke affect subclinical vascular function

OBJECTIVE

To evaluate whether vascular health in young children was associated with exposure to a 6-week episode of coal mine fire smoke or environmental tobacco smoke (ETS) in a retrospective cohort study.

METHODS

Three years after a coal mine fire in Victoria, Australia, we investigated the vascular health of children either in utero (n=75) or aged <2 years (postnatal exposure, n=96) at the time of the fire. The outcomes were the carotid intima-media thickness (IMT) and pulse wave velocity (PWV). The mean and peak daily particulate matter <2.5 µm in diameter (PM_2.5) exposures were estimated based on their daily locations throughout the fire period. Multivariable linear regression models were used to test for associations between the fire-related PM_2.5 and outcomes adjusted for relevant covariates including ETS.

RESULTS

In the postnatal-exposure group, each 10 µg/m³ increase in mean PM_2.5 level was independently positively associated with PWV (β=0.116, p=0.028). When these two groups were combined, there was an association between mean PM_2.5 and increased PWV in those children who had ETS exposure (β=0.148, p=0.033) or whose mothers smoked (β=0.151, p=0.011), but not in those not exposed to ETS or maternal smoking.

CONCLUSIONS

Three years after a coal mine fire, infants aged up to 2 years at the time of exposure have increases in vascular stiffness. Although no adverse effects were observed in the in uterus exposure group, further follow-up study is needed to elucidate the long-term effects of coal mine fire smoke exposure.

The impact of periconceptional maternal lifestyle on clinical features and biomarkers of placental development and function: a systematic review

BACKGROUND

Worldwide, placenta-related complications contribute to adverse pregnancy outcomes, such as pre-eclampsia, fetal growth restriction and preterm birth, with implications for the future health of mothers and offspring. The placenta develops in the periconception period and forms the interface between mother and embryo/fetus. An unhealthy periconceptional maternal lifestyle, such as smoking, alcohol and under- and over-nutrition, can detrimentally influence placental development and function.

OBJECTIVE AND RATIONALE

The impact of maternal lifestyle on placental health is largely unknown. Therefore, we aim to summarize the evidence of the impact of periconceptional maternal lifestyle on clinical features and biomarkers of placental development and function throughout pregnancy.

SEARCH METHODS

A comprehensive search in Medline, Embase, Pubmed, The Cochrane Library Web of Science and Google Scholar was conducted. The search strategy included keywords related to the maternal lifestyle, smoking, alcohol, caffeine, nutrition (including folic acid supplement intake) and body weight. For placental markers throughout pregnancy, keywords related to ultrasound imaging, serum biomarkers and histological characteristics were used. We included randomized controlled trials and observational studies published between January 2000 and March 2017 and restricted the analysis to singleton pregnancies and maternal periconceptional lifestyle. Methodological quality was scored using the ErasmusAGE tool. A protocol of this systematic review has been registered in PROSPERO International prospective register of systematic reviews (PROSPERO 2016:CRD42016045596).

OUTCOMES

Of 2593 unique citations found, 82 studies were included. The median quality score was 5 (range: 0-10). The findings revealed that maternal smoking was associated with lower first-trimester placental vascularization flow indices, higher second- and third-trimester resistance of the uterine and umbilical arteries and lower resistance of the middle cerebral artery. Although a negative impact of smoking on placental weight was expected, this was less clear. Alcohol use was associated with a lower placental weight. One study described higher second- and third-trimester placental growth factor (PlGF) levels after periconceptional alcohol use. None of the studies looked at caffeine intake. Adequate nutrition in the first trimester, periconceptional folic acid supplement intake and strong adherence to a Mediterranean diet, were all associated with a lower resistance of the uterine and umbilical arteries in the second and third trimester. A low caloric intake resulted in a lower placental weight, length, breadth, thickness, area and volume. Higher maternal body weight was associated with a larger placenta measured by ultrasound in the second and third trimester of pregnancy or weighed at birth. In addition, higher maternal body weight was associated with decreased PlGF-levels.

WIDER IMPLICATIONS

Evidence of the impact of periconceptional maternal lifestyle on placental health was demonstrated. However, due to poorly defined lifestyle exposures and time windows of investigation, unstandardized measurements of placenta-related outcomes and small sample sizes of the included studies, a cautious interpretation of the effect estimates is indicated. We suggest that future research should focus more on physiological consequences of unhealthy lifestyle during the critical periconception window. Moreover, we foresee that new evidence will support the development of lifestyle interventions to improve the health of mothers and their offspring from the earliest moment in life.

Why Do Intrauterine Exposure to Air Pollution and Cigarette Smoke Increase the Risk of Asthma?

The prevalence of childhood asthma is increasing worldwide and increased in utero exposure to environmental toxicants may play a major role. As current asthma treatments are not curative, understanding the mechanisms underlying the etiology of asthma will allow better preventative strategies to be developed. This review focuses on the current understanding of how in utero exposure to environmental factors increases the risk of developing asthma in children. Epidemiological studies show that maternal smoking and particulate matter exposure during pregnancy are prominent risk factors for the development of childhood asthma. We discuss the changes in the developing fetus due to reduced oxygen and nutrient delivery affected by intrauterine environmental change. This leads to fetal underdevelopment and abnormal lung structure. Concurrently an altered immune response and aberrant epithelial and mesenchymal cellular function occur possibly due to epigenetic reprograming. The sequelae of these early life events are airway remodeling, airway hyperresponsiveness, and inflammation, the hallmark features of asthma. In summary, exposure to inhaled oxidants such as cigarette smoking or particulate matter increases the risk of childhood asthma and involves multiple mechanisms including impaired fetal lung development (structural changes), endocrine disorders, abnormal immune responses, and epigenetic modifications. These make it challenging to reduce the risk of asthma, but knowledge of the mechanisms can still help to develop personalized medicines.

Prenatal air pollution exposure, smoking, and uterine vascular resistance

BACKGROUND

Prenatal exposure to air pollution and smoking increases the risk of pregnancy complications and adverse birth outcomes, but pathophysiologic mechanisms are still debated. Few studies to date have examined the influence of air pollution on uterine vascular resistance and no studies have examined the independent impact of these exposures. We aimed to assess the impact of prenatal exposure to traffic-related air pollution and smoking on uterine vascular resistance.

METHODS

Our study included 566 pregnant women recruited between 1993 and 1996 in Los Angeles who completed visits at three gestational ages. Information on smoking was collected and uterine vascular resistance was measured at each visit by Doppler ultrasound. We calculated three resistance indices: the resistance index (RI), the pulsatility index (PI), and the systolic/diastolic (S/D) ratio. We estimated exposure to NO2 at the home address of the mother using a land use regression (LUR) model and to NOx using CALINE4 air dispersion modeling. We used generalized linear mixed models to estimate the effects of air pollution and smoking on uterine vascular resistance indices.

RESULTS

LUR-derived NO2 and CALINE4-derived NOx exposure increased the risk of high uterine artery resistance in late pregnancy. Smoking during pregnancy also increased the risk of higher uterine resistance and contributed to bilateral notching in mid-pregnancy.

CONCLUSION

Our results suggest that uterine vascular resistance is a mechanism underlying the association between smoking and air pollution, and adverse birth outcomes.

Cardiovascular Consequences of Childhood Secondhand Tobacco Smoke Exposure: Prevailing Evidence, Burden, and Racial and Socioeconomic Disparities: A Scientific Statement From the American Heart Association

BACKGROUND

Although public health programs have led to a substantial decrease in the prevalence of tobacco smoking, the adverse health effects of tobacco smoke exposure are by no means a thing of the past. In the United States, 4 of 10 school-aged children and 1 of 3 adolescents are involuntarily exposed to secondhand tobacco smoke (SHS), with children of minority ethnic backgrounds and those living in low-socioeconomic-status households being disproportionately affected (68% and 43%, respectively). Children are particularly vulnerable, with little control over home and social environment, and lack the understanding, agency, and ability to avoid SHS exposure on their own volition; they also have physiological or behavioral characteristics that render them especially susceptible to effects of SHS. Side-stream smoke (the smoke emanating from the burning end of the cigarette), a major component of SHS, contains a higher concentration of some toxins than mainstream smoke (inhaled by the smoker directly), making SHS potentially as dangerous as or even more dangerous than direct smoking. Compelling animal and human evidence shows that SHS exposure during childhood is detrimental to arterial function and structure, resulting in premature atherosclerosis and its cardiovascular consequences. Childhood SHS exposure is also related to impaired cardiac autonomic function and changes in heart rate variability. In addition, childhood SHS exposure is associated with clustering of cardiometabolic risk factors such as obesity, dyslipidemia, and insulin resistance. Individualized interventions to reduce childhood exposure to SHS are shown to be at least modestly effective, as are broader-based policy initiatives such as community smoking bans and increased taxation.

PURPOSE

The purpose of this statement is to summarize the available evidence on the cardiovascular health consequences of childhood SHS exposure; this will support ongoing efforts to further reduce and eliminate SHS exposure in this vulnerable population. This statement reviews relevant data from epidemiological studies, laboratory-based experiments, and controlled behavioral trials concerning SHS and cardiovascular disease risk in children. Information on the effects of SHS exposure on the cardiovascular system in animal and pediatric studies, including vascular disruption and platelet activation, oxidation and inflammation, endothelial dysfunction, increased vascular stiffness, changes in vascular structure, and autonomic dysfunction, is examined.

CONCLUSIONS

The epidemiological, observational, and experimental evidence accumulated to date demonstrates the detrimental cardiovascular consequences of SHS exposure in children.

IMPLICATIONS

Increased awareness of the adverse, lifetime cardiovascular consequences of childhood SHS may facilitate the development of innovative individual, family-centered, and community health interventions to reduce and ideally eliminate SHS exposure in the vulnerable pediatric population. This evidence calls for a robust public health policy that embraces zero tolerance of childhood SHS exposure.

Utilizing Longitudinal Measures of Fetal Growth to Create a Standard Method to Assess the Impacts of Maternal Disease and Environmental Exposure

Impaired or suboptimal fetal growth is associated with an increased risk of perinatal morbidity and mortality. By utilizing readily available clinical data on the relative size of the fetus at multiple points in pregnancy, including delivery, future epidemiological research can improve our understanding of the impacts of maternal, fetal, and environmental factors on fetal growth at different windows during pregnancy. This study presents mean and standard deviation ultrasound measurements from a clinically representative US population that can be utilized for creating Z-scores to this end. Between 2006 and 2012, 18, 904 non-anomalous pregnancies that received prenatal care, first and second trimester ultrasound evaluations, and ultimately delivered singleton newborns at Brigham and Women's hospital in Boston were used to create the standard population. To illustrate the utility of this standard, we created Z-scores for ultrasound and delivery measurements for a cohort study population and examined associations with factors known to be associated with fetal growth. In addition to cross-sectional regression models, we created linear mixed models and generalized additive mixed models to illustrate how these scores can be utilized longitudinally and for the identification of windows of susceptibility. After adjustment for a priori confounders, maternal BMI was positively associated with increased fetal size beginning in the second trimester in cross-sectional models. Female infants and maternal smoking were associated with consistently reduced fetal size in the longitudinal models. Maternal age had a non-significant association with increased size in the first trimester that was attenuated as gestation progressed. As the growth measurements examined here are widely available in contemporary obstetrical practice, these data may be abstracted from medical records by investigators and standardized with the population means presented here. This will enable easy extension of clinical data to epidemiologic studies investigating novel maternal, fetal, and environmental factors that may impact fetal growth.

Impact of maternal smoking during pregnancy on microvasculature in childhood. The Generation R Study

BACKGROUND

Fetal exposure to maternal smoking is associated with an adverse cardiovascular risk profile in later life. Early microvasculature adaptations might be part of the underlying mechanisms for these associations.

AIMS

The aim of this study was to examine the influence of maternal smoking during pregnancy on retinal vessel calibers in children.

STUDY DESIGN

We performed a population-based prospective cohort study among 3564 school-age children. Maternal smoking patterns during pregnancy were assessed by questionnaires.

OUTCOME MEASURES

At the median age of 6.0 years (95% range 5.8, 8.0 years), we measured childhood retinal vessel calibers from retinal photographs.

RESULTS

No differences were observed in childhood retinal arteriolar and venular calibers among offspring from mothers who smoked in the first trimester and mothers who continued smoking throughout pregnancy, as compared to mothers who did not smoke during pregnancy. Also, no dose-dependent associations of the number of cigarettes smoked during pregnancy with childhood retinal vessel calibers were present.

CONCLUSION

Maternal smoking during pregnancy did not influence childhood retinal arteriolar and venular calibers. The mechanisms linking fetal smoke exposure with cardiovascular risk factors in later life may include other mechanisms than structural microvasculature adaptations.

Obstetric conditions and the placental weight ratio

INTRODUCTION

To elucidate how obstetric conditions are associated with atypical placental weight ratios (PWR)s in infants born: (a) ≥37 weeks gestation; (b) at ≥33 but <37 weeks gestation; and (c) <33 weeks gestation.

METHODS

The study included all in-hospital singleton births in London, Ontario between June 1, 2006 and March 31, 2011. PWR was assessed as <10th or >90th percentile by gestational age-specific local population standards. Multivariable analysis was carried out using multinomial logistic regression with blockwise variable entry in order of temporality.

RESULTS

Baseline factors and maternal obstetric conditions associated with PWR <10th percentile were: increasing maternal height, overweight and obese body mass indexes (BMI), large for gestational age infants, smoking, and gestational diabetes. Obstetric factors associated with PWR >90th percentile were: underweight, overweight and obese BMIs, smoking, preeclampsia, placenta previa, and placental abruption. In particular, indicators of hypoxia and altered placental function were generally associated with elevated PWR at all gestations.

DISCUSSION

An association between obstetric conditions associated with fetal hypoxia and PWR ≥90th percentile was illustrated.

CONCLUSIONS

The multivariable findings suggest that the PWR is similarly increased regardless of the etiology of the hypoxia.

A review on the genetic, environmental, and lifestyle aspects of the early-life origins of cardiovascular disease

This article is a comprehensive review on developmental origins of health and disease regarding various factors related to the origins of cardiovascular diseases from early life. It presents a summary of the impacts of various factors such as epigenetics; gene-environment interaction; ethnic predisposition to cardiovascular diseases and their underlying risk factors; prenatal factors; fetal programming; maternal weight status and weight gain during pregnancy; type of feeding during infancy; growth pattern during childhood; obesity; stunting; socioeconomic status; dietary and physical activity habits; active, secondhand, and thirdhand smoking, as well as environmental factors including air pollution and global climate change on the development and progress of cardiovascular diseases and their risk factors. The importance of early identification of predisposing factors for cardiovascular diseases for primordial and primary prevention of cardiovascular diseases from early life is highlighted.

Air pollution exposure and markers of placental growth and function: the generation R study

BACKGROUND

Air pollution exposure during pregnancy might affect placental growth and function, perhaps leading to pregnancy complications.

OBJECTIVE

We prospectively evaluated the associations of maternal air pollution exposure with markers of placental growth and function among 7,801 pregnant women in the Netherlands.

METHODS

We estimated levels of particulate matter ≤ 10 µm in aerodynamic diameter (PM10) and nitrogen dioxide (NO2) at the home address for different periods during pregnancy using dispersion modeling techniques. Pro- and anti-angiogenic factors [placental growth factor (PlGF) and soluble fms-like tyrosine kinase 1 (sFlt-1), respectively] were measured in first- and second-trimester maternal blood and in fetal cord blood samples at delivery. Pulsatility index of the uterine and umbilical arteries was measured by Doppler ultrasound in second and third trimester, and notching was assessed in third trimester. Placenta weight and birth weight were obtained from medical records.

RESULTS

Higher PM10 and NO2 exposure levels were associated with lower second-trimester maternal sFlt-1 and PlGF levels. PM10 and NO2 exposures averaged over total pregnancy were associated with higher sFlt-1 and lower PlGF levels in fetal cord blood, consistent with an anti-angiogenic state. PM10 and NO2 exposures were not consistently associated with second- or third-trimester placental resistance indices. NO2 exposure was associated with third-trimester notching (odds ratio 1.33; 95% CI: 0.99, 1.78 per 10-µg/m3 increase in the prior 2 months). PM10 and NO2 exposures were associated with lower placenta weight (-11.8 g; 95% CI: -20.9, -2.7, and -10.7 g; 95% CI: -19.0, -2.4, respectively, per 10-µg/m3 increase in the prior 2 months), but not with placenta to birth weight ratio.

CONCLUSIONS

Our results suggest that maternal air pollution exposure may influence markers of placental growth and function. Future studies are needed to confirm these findings and explore the maternal and fetal consequences.

Placental mitochondrial DNA content and particulate air pollution during in utero life

BACKGROUND

Studies emphasize the importance of particulate matter (PM) in the formation of reactive oxygen species and inflammation. We hypothesized that these processes can influence mitochondrial function of the placenta and fetus.

OBJECTIVE

We investigated the influence of PM₁₀ exposure during pregnancy on the mitochondrial DNA content (mtDNA content) of the placenta and umbilical cord blood.

METHODS

DNA was extracted from placental tissue (n = 174) and umbilical cord leukocytes (n = 176). Relative mtDNA copy numbers (i.e., mtDNA content) were determined by real-time polymerase chain reaction. Multiple regression models were used to link mtDNA content and in utero exposure to PM₁₀ over various time windows during pregnancy.

RESULTS

In multivariate-adjusted analysis, a 10-µg/m³ increase in PM₁₀ exposure during the last month of pregnancy was associated with a 16.1% decrease [95% confidence interval (CI): -25.2, -6.0%, p = 0.003] in placental mtDNA content. The corresponding effect size for average PM₁₀ exposure during the third trimester was 17.4% (95% CI: -31.8, -0.1%, p = 0.05). Furthermore, we found that each doubling in residential distance to major roads was associated with an increase in placental mtDNA content of 4.0% (95% CI: 0.4, 7.8%, p = 0.03). No association was found between cord blood mtDNA content and PM₁₀ exposure.

CONCLUSIONS

Prenatal PM₁₀ exposure was associated with placental mitochondrial alterations, which may both reflect and intensify oxidative stress production. The potential health consequences of decreased placental mtDNA content in early life must be further elucidated.

Angiogenic and fibrinolytic factors in blood during the first half of pregnancy and adverse pregnancy outcomes

OBJECTIVE

To estimate whether the imbalance of angiogenic factors (soluble fms-like tyrosine kinase-1, placental growth factor) and fibrinolytic factors (plasminogen activator inhibitor-2 [PAI-2]) might affect placentation in early pregnancy.

METHODS

We studied the associations of maternal soluble fms-like tyrosine kinase-1, placental growth factor, and PAI-2 concentrations in the first trimester (before 18 weeks of gestation) and soluble fms-like tyrosine kinase-1 and placental growth factor concentrations in the second trimester (18-25 weeks of gestation) with placental function and adverse pregnancy outcomes. This study was embedded in a population-based prospective cohort study. Data were used from 7,519 women. Biomarker concentrations were divided into deciles and evaluated in multivariable linear and logistic regression models.

RESULTS

First-trimester high soluble fms-like tyrosine kinase-1 was associated with a 5.2% lower uterine artery index in the second-trimester and a 1.6% higher birth weight (55 g, confidence interval [CI] 15-95). Neither in the first nor in the second trimester were soluble fms-like tyrosine kinase-1 concentrations significantly associated with preeclampsia. First-trimester low placental growth factor was associated with a 6.1% higher uterine artery index and a 3.4% lower birth weight (-115 g, CI -157 to -74). First-trimester low placental growth factor was associated with fetal growth restriction (odds ratio [OR] 2.62, CI 1.68-4.08) and preeclampsia (OR 2.46, CI 1.49-4.08). First-trimester low PAI-2 was associated with a 1.9% higher uterine artery index and a 2.7% lower birth weight (-94 g, CI -136 to -51). First-trimester low PAI-2 was associated with a higher risk of fetal growth restriction (OR 2.22, CI 1.39-3.55).

CONCLUSION

First-half-of-pregnancy concentrations of soluble fms-like tyrosine kinase-1, placental growth factor, and PAI-2 are associated with uteroplacental vascular resistance, placental weight, and birth weight. Moreover, first-trimester placental growth factor and PAI-2 are associated with an increased risk of adverse pregnancy outcomes.

LEVEL OF EVIDENCE

II.

Effects of maternal smoking during pregnancy on offspring blood pressure in late adolescence

OBJECTIVES

Previous studies suggest that maternal smoking during pregnancy is associated with elevated offspring blood pressure during childhood. We aimed to investigate whether this association remained in late adolescence and, if so, whether it could be attributed to an intrauterine effect or to familial confounding.

METHODS

We used a national cohort of 87,223 young Swedish men born between 1983 and 1988 with information on both maternal smoking during pregnancy and blood pressure at military conscription. The cohort included 780 full brothers discordant for maternal smoking. Generalized estimation equations were used to estimate regression coefficients (β) with 95% confidence intervals (95% CIs).

RESULTS

We found a small but significant increase in both SBP and DBP for young men whose mothers had been daily smokers during pregnancy compared with sons of nonsmoking mothers: 0.26 (95% CI 0.09 to 0.44) and 0.45 mmHg (95% CI 0.31 to 0.59) for SBP and DBP, respectively. In a within-sibling analysis comparing full brothers discordant for maternal smoking exposure, point estimates were similar but not statistically significant: 0.85 (95% CI -0.19 to 1.90) for DBP and 0.81 (-0.56 to 2.19) for SBP.

CONCLUSION

Maternal smoking during pregnancy is associated with a small but statistically significant increase in offspring blood pressure in late adolescence. Because the association does not appear to be explained by familial confounding, our results support an intrauterine effect of prenatal smoking exposure on blood pressure in late adolescence.

A common genetic variant at 15q25 modifies the associations of maternal smoking during pregnancy with fetal growth: the generation R study

OBJECTIVE

Maternal smoking during pregnancy is associated with fetal growth retardation. We examined whether a common genetic variant at chromosome 15q25 (rs1051730), which is known to be involved in nicotine metabolism, modifies the associations of maternal smoking with fetal growth characteristics.

METHODS

This study was performed in 3,563 European mothers participating in a population-based prospective cohort study from early pregnancy onwards. Smoking was assessed by postal questionnaires and fetal growth characteristics were measured by ultrasound examinations in each trimester of pregnancy.

RESULTS

Among mothers who did not smoke during pregnancy (82.9%), maternal rs1051730 was not consistently associated with any fetal growth characteristic. Among mothers who continued smoking during pregnancy (17.1%), maternal rs1051730 was not associated with head circumference. The T-allele of maternal rs1051730 was associated with a smaller second and third trimester fetal femur length [differences -0.23 mm (95%CI -0.45 to -0.00) and -0.41 mm (95%CI -0.69 to -0.13), respectively] and a smaller birth length [difference -2.61 mm (95%CI -5.32 to 0.11)]. The maternal T-allele of rs1051730 was associated with a lower third trimester estimated fetal weight [difference -33 grams (95%CI -55 to -10)], and tended to be associated with birth weight [difference -38 grams (95%CI -89 to 13)]. This association persisted after adjustment for smoking quantity.

CONCLUSIONS

Our results suggest that maternal rs1051730 genotype modifies the associations of maternal smoking during pregnancy with impaired fetal growth in length and weight. These results should be considered as hypothesis generating and indicate the need for large-scale genome wide association studies focusing on gene--fetal smoke exposure interactions.

Parental smoking and vascular damage in their 5-year-old children

BACKGROUND

The relation between smoke exposure in early life, the prenatal period in particular, and the vascular development of young children is largely unknown.

METHODS

Data from the birth cohort participating in the WHISTLER-Cardio study were used to relate the smoking of parents during pregnancy to subsequent vascular properties in their children. In 259 participating children who turned 5 years of age, parental smoking data were updated and children's carotid artery intima-media thickness (CIMT) and arterial wall distensibility were measured by using ultrasonography.

RESULTS

Children of mothers who had smoked throughout pregnancy had 18.8 μm thicker CIMT (95% confidence interval [CI] 1.1, 36.5, P = .04) and 15% lower distensibility (95% CI -0.3, -0.02, P = .02) after adjustment for child's age, maternal age, gender, and breastfeeding. The associations were not found in children of mothers who had not smoked in pregnancy but had smoked thereafter. The associations were strongest if both parents had smoked during pregnancy, with 27.7 μm thicker CIMT (95% CI 0.2, 55.3) and 21% lower distensibility (95% CI -0.4, -0.03).

CONCLUSION

Exposure of children to parental tobacco smoke during pregnancy affects their arterial structure and function in early life.

Cardiovascular and metabolic influences of fetal smoke exposure

Many epidemiological studies showed associations of low birth weight with cardiovascular disease, type 2 diabetes and obesity. The associations seem to be consistent and stronger among subjects with a postnatal catch up growth. It has been suggested that developmental changes in response to adverse fetal exposures might lead to changes in the fetal anatomy and physiology. These adaptations may be beneficial for short term, but may lead to common diseases in adulthood. Maternal smoking during pregnancy is one of the most important adverse fetal exposures in Western countries, and is known to be associated with a 150-200 g lower birth weight. An accumulating body of evidence suggests that maternal smoking during pregnancy might be involved in pathways leading to both low birth weight and common diseases, including cardiovascular disease, type 2 diabetes and obesity, in adulthood. In this review, we discuss epidemiological studies focused on the associations of maternal smoking with fetal growth and development and cardiovascular and metabolic disease in later life. We also discuss potential biological mechanisms, and challenges for future epidemiological studies.

Cardiovascular and metabolic influences of fetal smoke exposure

Many epidemiological studies showed associations of low birth weight with cardiovascular disease, type 2 diabetes and obesity. The associations seem to be consistent and stronger among subjects with a postnatal catch up growth. It has been suggested that developmental changes in response to adverse fetal exposures might lead to changes in the fetal anatomy and physiology. These adaptations may be beneficial for short term, but may lead to common diseases in adulthood. Maternal smoking during pregnancy is one of the most important adverse fetal exposures in Western countries, and is known to be associated with a 150–200 g lower birth weight. An accumulating body of evidence suggests that maternal smoking during pregnancy might be involved in pathways leading to both low birth weight and common diseases, including cardiovascular disease, type 2 diabetes and obesity, in adulthood. In this review, we discuss epidemiological studies focused on the associations of maternal smoking with fetal growth and development and cardiovascular and metabolic disease in later life. We also discuss potential biological mechanisms, and challenges for future epidemiological studies.

Assessment of maternal smoking status during pregnancy and the associations with neonatal outcomes

INTRODUCTION

Single assessment of smoking during pregnancy may lead to misclassification due to underreporting or failure of smoking cessation. We examined the percentage of mothers who were misclassified in smoking status based on single assessment, as compared with repeated assessment, and whether this misclassification leads to altered effect estimates for the associations between maternal smoking and neonatal complications.

METHODS

This study was performed in 5,389 mothers participating in a prospective population-based cohort study in the Netherlands. Smoking status was assessed 3 times during pregnancy using questionnaires. Information on birth weight and neonatal complications was obtained from hospital records.

RESULTS

For categorizing mothers per smoking status, Cohen's Kappa coefficient was .86 (p < .001) between single and repeated assessments. Of all mothers who reported nonsmoking or first trimester-only smoking in early pregnancy, 1.7% (70 of 4,141) and 33.7% (217 of 643), respectively, were reclassified to continued smoking based on repeated assessment. Younger, shorter lower educated mothers who had non-European ethnicity experienced more stress, consumed more alcohol, and did not use folic acid supplements had higher risk of underreporting their smoking status or failure of smoking cessation. Marginal differences were found on the associations of maternal smoking with neonatal complications between single or repeated assessment.

CONCLUSIONS

Our results suggest that single assessment of smoking during pregnancy leads to underestimation of the continued smoking prevalence, especially among mothers who reported quitting smoking in first trimester. However, this underestimation does not materially change the effect estimates for the associations between maternal smoking and neonatal outcomes.

Nicotine induced CpG methylation of Pax6 binding motif in StAR promoter reduces the gene expression and cortisol production

Steroidogenic acute regulatory protein (StAR) mediates the rate-limiting step in the synthesis of steroid hormones, essential to fetal development. We have reported that the StAR expression in fetal adrenal is inhibited in a rat model of nicotine-induced intrauterine growth retardation (IUGR). Here using primary human fetal adrenal cortex (pHFAC) cells and a human fetal adrenal cell line NCI-H295A, we show that nicotine inhibits StAR expression and cortisol production in a dose- and time-dependent manner, and prolongs the inhibitory effect on cells proliferating over 5 passages after termination of nicotine treatment. Methylation detection within the StAR promoter region uncovers a single site CpG methylation at nt -377 that is sensitive to nicotine treatment. Nicotine-induced alterations in frequency of this point methylation correlates well with the levels of StAR expression, suggesting an important role of the single site in regulating StAR expression. Further studies using bioinformatics analysis and siRNA approach reveal that the single CpG site is part of the Pax6 binding motif (CGCCTGA) in the StAR promoter. The luciferase activity assays validate that Pax6 increases StAR gene expression by binding to the glucagon G3-like motif (CGCCTGA) and methylation of this site blocks Pax6 binding and thus suppresses StAR expression. These data identify a nicotine-sensitive CpG site at the Pax6 binding motif in the StAR promoter that may play a central role in regulating StAR expression. The results suggest an epigenetic mechanism that may explain how nicotine contributes to onset of adult diseases or disorders such as metabolic syndrome via fetal programming.