Associations of maternal iron intake and hemoglobin in pregnancy with offspring vascular phenotypes and adiposity at age 10: findings from the Avon Longitudinal Study of Parents and Children

Impact of perinatal factors on biomarkers of cardiovascular disease risk in preadolescent children

BACKGROUND

This review aims to summarize associations of the perinatal environment with arterial biophysical properties in childhood, to elucidate possible perinatal origins of adult cardiovascular disease (CVD).

METHODS

A systematic search of PubMed database was performed (December 2020). Studies exploring associations of perinatal factors with arterial biophysical properties in children 12 years old or less were included. Properties studied included: pulse wave velocity; arterial stiffness or distensibility; augmentation index; intima-media thickness of aorta (aIMT) or carotids; endothelial function (laser flow Doppler, flow-mediated dilatation). Two reviewers independently performed study selection and data extraction.

RESULTS

Fifty-two of 1084 identified records were included. Eleven studies explored associations with prematurity, 14 explored maternal factors during pregnancy, and 27 explored effects of low birth weight, small-for-gestational age and foetal growth restriction (LBW/SGA/FGR). aIMT was consistently higher in offspring affected by LBW/SGA/FGR in all six studies examining this variable. The cause of inconclusive or conflicting associations found with other arterial biophysical properties and perinatal factors may be multifactorial: in particular, measurements and analyses of related properties differed in technique, equipment, anatomical location, and covariates used.

CONCLUSION

aIMT was consistently higher in LBW/SGA/FGR offspring, which may relate to increased long-term CVD risk. Larger and longer term cohort studies may help to elucidate clinical significance, particularly in relation to established CVD risk factors. Experimental studies may help to understand whether lifestyle or medical interventions can reverse perinatal changes aIMT. The field could be advanced by validation and standardization of techniques assessing arterial structure and function in children.

Early life determinants of arterial stiffness in neonates, infants, children and adolescents: A systematic review and meta-analysis

BACKGROUND AND AIMS

Certain exposures and risk factors during the first 1,000 days of life are known to influence future cardiovascular disease (CVD) risk. Pulse wave velocity (PWV) is a measure of arterial stiffness and a recognised surrogate marker of CVD. We performed a systematic review and meta-analyses to investigate whether early life exposures were associated with increased PWV compared with controls in youth.

METHODS

Databases AMED, MEDLINE, EMBASE, CINAHL and Scopus were searched from inception until February 2022.

ELIGIBILITY CRITERIA

observational controlled studies in youth aged <20 years with risk factors/exposure during the first 1,000 days and PWV measurement. This review is registered with PROSPERO (CRD42019137559). Outcome data were pooled using random-effects meta-analysis. Meta-regression was used to investigate potential confounders.

RESULTS

We identified 24 eligible studies. Age of participants ranged from 1-day to 19-years at time of PWV assessment. Exposures included pre-term birth, small for gestational age (SGA), maternal diabetes and assisted reproductive technologies, none of which were significantly associated with PWV in meta-analysis. Sub-group analysis by age demonstrated increased PWV in childhood and adolescence in those exposed to maternal diabetes or born SGA. In meta-regression of pre-term studies, higher prevalence of SGA was associated with increased PWV compared with controls (p = 0.034, R² = 1).

CONCLUSIONS

We found limited evidence that youth exposed to maternal diabetes or born SGA have increased PWV, consistent with increased future CVD risk. These changes in PWV appear to manifest in later childhood and adolescence. Further research is required to better understand the observed relationships.

Associations between maternal iron supplementation in pregnancy and offspring growth and cardiometabolic risk outcomes in infancy and childhood

It was previously observed that maternal iron supplementation in pregnancy was associated with increased offspring size and adiposity at birth, possibly mediated through increased risk of gestational diabetes. In this study we investigated potential long-term associations of maternal iron supplementation in pregnancy with offspring growth in infancy, and growth and cardiometabolic risk factors in mid-childhood to seek evidence of nutritional programming. Using a nested case-control format, markers of growth and adiposity were measured at 3, 12 and 24 months of age in 341 infants from the Cambridge Baby Growth Study whose mothers supplemented with iron in pregnancy and 222 infants whose mothers did not. Measures of growth, glucose tolerance (using a 30 minute 1.75 g glucose/kg body weight oral glucose tolerance test), insulin sensitivity (HOMA IR) and blood pressure were collected in 122 and 79 of these children, respectively, at around 9.5 years of age. In infancy adiposity-promoting associations with maternal iron supplementation in pregnancy were evident at 3 months of age (e.g. mean difference in skinfold thickness: β = +0.15 mm, p = 0.02, in n = 341 whose mothers supplemented versus 222 that did not; waist circumference: β = +0.7 cm, p = 0.04, in n = 159 and 78, respectively) but differences lessened after this time (e.g. 3–12 month change in mean difference in skinfold thickness: β = -0.2 mm, p = 0.03, in n = 272 and 178, respectively). At ~9.5 years of age children whose mothers supplemented with iron in pregnancy had lower mean arterial blood pressures (β = -1.0 mmHg, p = 0.03, in n = 119 and 78, respectively). There were no apparent differences in markers of growth or other cardiometabolic factors. These results suggest that most of the associations of maternal iron supplementation in pregnancy on growth and adiposity evident at birth disappear during infancy, but there may be some evidence of long-term nutritional programming of blood pressure in mid-childhood.

Maternal dietary diversity and nutritional adequacy in relation with anthropometric measurements of newborns at birth: a cohort study in Tehran city

Background

Maternal dietary intake during pregnancy plays an important role in fetal development and birth outcomes. The aim of the present study was to determine maternal dietary diversity and Nutritional adequacy in relation with anthropometric measurements of newborn at birth as a cohort study in Tehran city.

Methods

This prospective cohort study, was conducted by participation of 585 pregnant women referred to public health centers and hospitals covered by Shahid Beheshti, Tehran and Iran Universities in Tehran City. Using face-to-face interviews, general characteristics were obtained by questionnaire. Pre-pregnancy dietary intake was measured by a 168-item semi-quantitative food frequency questionnaire at the first visit, and dietary intake during pregnancy was measured by 2 non-consecutive 24-h food recall (one holiday and one regular day) at 31–34 weeks. Maternal height and weight were measured using standard tools and protocol at the first visit, and maternal weight at the end of pregnancy and data related to neonatal anthropometric indices were collected from mothers and neonates health records in the Sib electrical system. By applying SPSS software (version 23) the association was analyzed by linear regression with adjusting for confounding factors. P-value< 0.05 was considered as significant.

Results

Mean ± standard deviation of body mass index (BMI) of pre-pregnancy, pregnancy weight gain, BMI for age z-score (BAZ) at birth of infants were 24.52 ± 4.12, 12.16 ± 6.85 kg and − 0.61 ± 1.48, respectively. Mean ± SD of the Dietary Diversity Score (DDS) and Mean Adequacy Ratio (MAR) before and during pregnancy were 5.31 ± 1.11, vs.5.23 ± 1.42 and 289.85 ± 113.12 vs. 371.07 ± 197.28, respectively. After adjusting for confounding factors DDS in the third trimester of pregnancy was inversely correlated with WAZ (B = -0.16, 95% CI = - 0.23_0.30) and BAZ (B = − 0.24, 95% CI = - 0.06_0. 42) at birth, MAR of pre-pregnancy (B = − 0.001, 95% CI = - 0.002_0.00) and in the third trimester of pregnancy (B = − 0.18, 95% CI = - 0.35_0.004) were negatively associated with WAZ at birth.

Conclusion

The findings showed that maternal nutritional status (dietary diversity and nutritional adequacy) before and during pregnancy were correlated with neonatal anthropometric indices at birth.

Associations between Maternal Iron Supplementation in Pregnancy and Changes in Offspring Size at Birth Reflect Those of Multiple Micronutrient Supplementation

It was previously observed that in a population of a high-income country, dietary multiple micronutrient supplementation in pregnancy was associated with an increased risk of gestational diabetes (GDM) and increased offspring size at birth. In this follow-up study, we investigated whether similar changes are observed with dietary iron supplementation. For this we used the prospective Cambridge Baby Growth Study with records of maternal GDM status, nutrient supplementation, and extensive offspring birth size measurements. Maternal iron supplementation in pregnancy was associated with GDM development (risk ratio 1.67 (1.01-2.77), p = 0.048, n = 677) as well as offspring size and adiposity (n = 844-868) at birth in terms of weight (β' = 0.078 (0.024-0.133); p = 0.005), head circumference (β' = 0.060 (0.012-0.107); p = 0.02), body mass index (β' = 0.067 (0.014-0.119); p = 0.01), and various skinfold thicknesses (β' = 0.067-0.094; p = 0.03-0.003). In a subset of participants for whom GDM statuses were available, all these associations were attenuated by adjusting for GDM. Iron supplementation also attenuated the associations between multiple micronutrient supplementation and these same measures. These results suggest that iron supplementation may mediate the effects associated with multiple micronutrient supplementation in pregnancy in a high-income country, possibly through the increased risk of developing GDM.

Association of Hemoglobin and Hematocrit Levels during Pregnancy and Maternal Dietary Iron Intake with Allergic Diseases in Children: The Japan Environment and Children's Study (JECS)

Few epidemiologic studies have examined the role of maternal iron status in allergic diseases in offspring and findings have been inconsistent. We used a large birth cohort in Japan to explore the association of the markers for maternal iron status (maternal hemoglobin, hematocrit and dietary iron intake during pregnancy) with allergy development in offspring during early childhood. We analyzed information on children age 0–3 years from the Japan Environment and Children’s Study (JECS). We used logistic models and generalized estimating equation models to evaluate the effect of maternal hemoglobin and hematocrit levels and dietary iron intake on allergies in children. Models were also fitted with propensity score-matched datasets. Data were collected for a total of 91,247 mother–child pairs. The prevalence (95% confidence interval) of low hemoglobin and hematocrit was 14.0% (13.7–14.2%) and 12.5% (12.3–12.8%), respectively. After adjusting confounders, low hemoglobin and hematocrit during pregnancy were not associated with childhood allergic outcomes. Findings from models with propensity score-matched datasets also indicated that children born to mothers with low hemoglobin or hematocrit levels during pregnancy did not have a higher risk of developing allergic conditions at 3 years old. We found no meaningful associations between low energy adjusted maternal dietary iron intake and allergies in children. In conclusion, using birth cohort data, we found no evidence supporting an association of low maternal hemoglobin, hematocrit and low dietary iron intake with allergy symptoms during early childhood. Further studies with more suitable proxy markers for blood iron status are needed.

Maternal prenatal thyroid function and trajectories of offspring emotional and behavioural problems: findings from the ALSPAC cohort

Maternal thyroid hormone may have impact on fetal brain development and consequently lead to offspring mental health problems. This study examined the role of maternal prenatal thyroid function on trajectories of offspring emotional and behavioural problems. Data were taken from the Avon Longitudinal Study of Parents and Children. A total of 4839 mother-child pairs were included. Thyroid-stimulating hormone (TSH) levels, free thyroxine (FT4), and thyroid peroxidase antibodies (TPO-Ab) were assessed during the first trimester of pregnancy. Childhood emotional and behavioural problems were assessed using the Strengths and difficulties questionnaire. A group-based modelling approach was used to identify the different trajectories of offspring emotional and behavioural problems reported by parents over four waves of measurement at age 3.5 (42 months), 6.75 (81 months), 9 and 11 years. Multinomial logistic regression was then used to test for an association between hormone levels and class membership. We identified four trajectories of offspring emotional and behavioural problems; normative-decreasing (49.7%), moderate-decreasing (35.7%), moderate-static (8.4%), and high-decreasing (6.2%) trajectory. There were no significant differences in the mean values of mother's FT4, TSH, and the proportion of mothers with positive TPO-Ab between trajectories. Univariable and multivariable multinomial logistic models showed no association between maternal thyroid function (FT4, TSH, and TPO-Ab) and the trajectories of offspring emotional and behavioural problems. The results of our study show that maternal thyroid parameters in a community population are not associated with trajectories of offspring emotional and behavioural problems.

The role of maternal prenatal thyroid function on offspring depression: Findings from the ALSPAC cohort

Maternal thyroid dysfunction during pregnancy may contribute to offspring neurobehavioral disorders. In this paper, we investigate the relationship between maternal thyroid function during pregnancy and offspring depression and anxiety. Data were taken from the Avon Longitudinal Study of Parents and Children. A total of 2,920 mother-child pairs were included. Thyroid-stimulating hormone levels, free thyroxine (FT4), and thyroid peroxidase antibodies were assessed during the first trimester of pregnancy because maternal supply is the only source of thyroid hormone for the fetus during the first 12 weeks of gestation. Child symptoms of depression and anxiety were assessed using the Development and Well-Being Assessment at ages 7.5 and 15 years. The odds of presenting with depression and anxiety were estimated using the generalized estimating equation. The level of FT4 during the first trimester of pregnancy was associated with child depression combined at ages 7.5 and 15 (odds ratio = 1.21, 95% confidence interval [1.00, 1.14]. An increase of 1 standard deviation of FT4 during pregnancy increased the odds of child depression by 28% after adjustment made for potential confounders. No association was found among maternal levels of thyroid-stimulating hormone, FT4, and thyroid peroxidase antibodies and childhood anxiety. In conclusion, increased levels of FT4 during the first trimester of pregnancy appear be linked to greater risk of offspring depression.

Maternal Prenatal Thyroid Function and Offspring ADHD: Findings From the ALSPAC Cohort

Thyroid hormone plays a pivotal role in the developing brain and may affect the development of attention deficit hyperactivity disorder (ADHD). This study aimed to examine the role of maternal thyroid function during pregnancy on offspring ADHD. A total of 2912 mother-child pairs were included from the Avon Longitudinal Study of Parents and Children. Thyroid parameters were assessed during the first trimester of pregnancy. Offspring ADHD was assessed using the Development and Well-Being Assessment at the ages of 7.5 and 15 years. The odds of presenting with ADHD were estimated using generalized estimating equations. Levels of thyroid-stimulating hormone (odds ratio [OR], 0.92; 95% confidence interval [CI], 0.48-1.75), free thyroxine (OR, 1.07; 95% CI, 0.87-1.32), and thyroid peroxidase antibodies (OR, 1.00; 95% CI, 0.80-1.25) were not associated with ADHD in children aged 7.5 and 15 years. This study showed no association between maternal thyroid function and offspring ADHD.

Prenatal iron exposure and childhood type 1 diabetes

Iron overload due to environmental or genetic causes have been associated diabetes. We hypothesized that prenatal iron exposure is associated with higher risk of childhood type 1 diabetes. In the Norwegian Mother and Child cohort study (n = 94,209 pregnancies, n = 373 developed type 1 diabetes) the incidence of type 1 diabetes was higher in children exposed to maternal iron supplementation than unexposed (36.8/100,000/year compared to 28.6/100,000/year, adjusted hazard ratio 1.33, 95%CI: 1.06-1.67). Cord plasma biomarkers of high iron status were non-significantly associated with higher risk of type 1 diabetes (ferritin OR = 1.05 [95%CI: 0.99-1.13] per 50 mg/L increase; soluble transferrin receptor: OR = 0.91 [95%CI: 0.81-1.01] per 0.5 mg/L increase). Maternal but not fetal HFE genotypes causing high/intermediate iron stores were associated with offspring diabetes (odds ratio: 1.45, 95%CI: 1.04, 2.02). Maternal anaemia or non-iron dietary supplements did not significantly predict type 1 diabetes. Perinatal iron exposures were not associated with cord blood DNA genome-wide methylation, but fetal HFE genotype was associated with differential fetal methylation near HFE. Maternal cytokines in mid-pregnancy of the pro-inflammatory M1 pathway differed by maternal iron supplements and HFE genotype. Our results suggest that exposure to iron during pregnancy may be a risk factor for type 1 diabetes in the offspring.

Maternal Iron Status in Pregnancy and Long-Term Health Outcomes in the Offspring

Iron is an essential micronutrient and is important not only in carrying oxygen but also to the catalytic activity of a variety of enzymes. In the fetus, it is vital to the synthesis of hemoglobin and in brain development. Iron deficiency (ID) anemia in pregnancy is a common problem, even in high-income country settings. Around 50% of pregnant women worldwide are anemic, with at least half of this burden due to ID. Iron supplements are widely recommended and used during pregnancy globally. However, the evidence on the extent of benefit they contribute to the offspring's health is not well established, and their routine use has its side effects and drawbacks. Dietary iron intake is difficult to assess accurately and it is unlikely to be sufficient to meet the demands of pregnancy if women start with inadequate body iron stores at conception. Evidence from experimental animal models suggests that maternal ID during pregnancy is associated with fetal growth restriction, as well as offspring obesity and high blood pressure later in life. The possible biological mechanisms for this observed association may be due to ID-induced changes in placental structure and function, enzyme expression, nutrient absorption, and fetal organ development. However, such evidence is limited in human studies. Prenatal ID in experimental animal models also adversely affected the developing brain structures, neurotransmitter systems, and myelination resulting in acute brain dysfunction during the period of deficiency and persistence of various postnatal neurobehavioral abnormalities as well as persistent dysregulation of some genes into adult life after iron repletion pointing to the possibility of gene expression changes. The evidence from human population studies is limited and heterogeneous and more research is needed in the future, investigating the effects of ID in pregnancy on future offspring health outcomes.

Pregnancy Requires Major Changes in the Quality of the Diet for Nutritional Adequacy: Simulations in the French and the United States Populations

BACKGROUND

Maternal nutrition is critical to the health of both mother and offspring, but there is a paucity of data on the nutritional adequacy of diets during pregnancy.

OBJECTIVE

Our objective was to identify to what extent pregnancy reduces the nutritional adequacy of the expecting mother's diet and if this nutritional gap can be resolved by simple quantitative or qualitative changes in the diet.

MATERIALS AND METHODS

We evaluated the observed overall nutritional adequacy of diets of French and American women of childbearing age participating in ENNS (n = 344) and NHANES (n = 563) using the probabilistic approach of the PANDiet system, resulting in a 100-point score. Then, we simulated the changes in the PANDiet scores of women of childbearing age who would remain on their diet during pregnancy. Finally, by either increasing the quantity of consumed foods or using eleven snacks recommended during pregnancy, we simulated the effect of a 150-kcal increase in the energy intake of French women.

RESULTS

Observed PANDiet scores were equal to 59.3 ± 7.0 and 58.8 ± 9.3 points respectively in France and in the US. Simulation of pregnancy for women of childbearing age led to a decrease in nutritional adequacy for key nutrients during pregnancy and resulted in reducing PANDiet scores by 3.3 ± 0.1 and 3.7 ± 0.1 points in France and in the US. Simulated 150-kcal increases in energy intake proved to be only partially effective in filling the gap both when the quantity of food consumed was increased and when recommended snacks were used.

CONCLUSIONS

The decrease in nutritional adequacy induced by pregnancy cannot be addressed by simply following generic dietary guidelines.

Infant Arterial Stiffness and Maternal Iron Status in Pregnancy: A UK Birth Cohort (Baby VIP Study)

BACKGROUND

In animal studies, iron deficiency during pregnancy has been linked to increased offspring cardiovascular risk. No previous population studies have measured arterial stiffness early in life to examine its association with maternal iron status.

OBJECTIVE

This study aimed to examine the association between maternal iron status in early pregnancy with infant brachio-femoral pulse wave velocity (PWV).

METHODS

The Baby VIP (Baby's Vascular Health and Iron in Pregnancy) study is a UK-based birth cohort which recruited 362 women after delivery from the Leeds Teaching Hospitals postnatal wards. Ferritin and transferrin receptor levels were measured in maternal serum samples previously obtained in the first trimester. Infant brachio-femoral PWV was measured during a home visit at 2-6 weeks.

RESULTS

Iron depletion (ferritin <15 μg/l) was detected in 79 (23%) women in early pregnancy. Infant PWV (mean = 6.7 m/s, SD = 1.3, n = 284) was neither associated with maternal ferritin (adjusted change per 10 μg/l = 0.02, 95% CI: -0.01, 0.1), nor with iron depletion (adjusted change = -0.2, 95% CI: -0.6, 0.2). No evidence of association was observed between maternal serum transferrin receptor level and its ratio to ferritin with infant PWV. Maternal anaemia (<11 g/dl) at ≤20 weeks' gestation was associated with a 1.0-m/s increase in infant PWV (adjusted 95% CI: 0.1, 1.9).

CONCLUSION

This is the largest study to date which has assessed peripheral PWV as a measure of arterial stiffness in infants. There was no evidence of an association between markers of maternal iron status early in pregnancy and infant PWV.