Effects of current size, postnatal growth, and birth size on blood pressure in early childhood

Longitudinal study of birthweight, blood pressure, and markers of arterial stiffness in children age six among the TIDES cohort

OBJECTIVE

Although some studies have observed an association between birthweight and cardiovascular disease in adulthood, fewer have investigated whether birthweight is linked to cardiovascular health in early childhood. This study assesses the association between birthweight and cardiovascular outcomes in children 6 years of age.

STUDY DESIGN

Birthweight, blood pressure (BP), and markers of arterial stiffness in children, including brachial artery distensibility and carotid-femoral pulse wave velocity (cfPWV), were obtained from 324 participants in The Infant Development and the Environment Study, a prospective multisite pregnancy cohort. Birthweight was converted into sex-specific birthweight-for-gestational-age (bw/ga) z -scores based on the INTERGROWTH-21st standard. Following 2017 American Academy of Pediatrics guidelines, SBP and DBP were transformed into sex, age, and height-specific z -scores. Associations between birthweight and cardiovascular outcomes were assessed using nested multivariable linear regression models among the overall and sex-stratified samples.

RESULTS

Among the overall sample, bw/ga z -score was positively associated with cfPWV [b = 0.11 m/s, 95% confidence interval (CI): 0.01 m/s, 0.21 m/s] in crude and adjusted models. No associations between birthweight and cardiovascular outcomes were detected among the sex-stratified analyses.

CONCLUSION

Overall, birthweight was not related to cardiovascular outcomes in children 6 years old. However, infants born with a higher birthweight may be at risk for higher cfPWV in childhood. Early intervention in pregnant people at risk of delivering high birthweight infants may be warranted if results are replicated.

Cannabidiol Exposure During Gestation Leads to Adverse Cardiac Outcomes Early in Postnatal Life in Male Rat Offspring

Introduction: Studies indicate that ∼7% of pregnant individuals in North America consume cannabis in pregnancy. Pre-clinical studies have established that maternal exposure to Δ9-tetrahydrocannabinol (THC; major psychoactive component in cannabis) leads to fetal growth restriction and impaired cardiac function in offspring. However, the effects of maternal exposure to cannabidiol (CBD; major non-euphoric constituent) on cardiac outcomes in offspring remain unknown. Therefore, our objective is to investigate the functional and underlying molecular impacts in the hearts of offspring exposed to CBD in pregnancy. Methods: Pregnant Wistar rats were exposed to either 3 or 30 mg/kg CBD or vehicle control i.p. daily from gestational day 6 to term. Echocardiography was used to assess cardiac function in male and female offspring at postnatal day (PND) 21. Furthermore, quantitative polymerase chain reaction (qPCR), immunoblotting, and bulk RNA-sequencing (RNA-seq) were performed on PND21 offspring hearts. Results: Despite no differences in the heart-to-body weight ratio, both doses of CBD led to reduced cardiac function exclusively in male offspring at 3 weeks of age. Underlying this, significant alterations in the expression of the endocannabinoid system (ECS; e.g., decreased cannabinoid receptor 2) were observed. In addition, bulk RNA-seq data demonstrated transcriptional pathways significantly enriched in mitochondrial function/metabolism as well as development. Conclusion: Collectively, we demonstrated for the first time that gestational exposure to CBD, a constituent perceived as safe, leads to early sex-specific postnatal cardiac deficits and alterations in the cardiac ECS in offspring.

Association of Birthweight with Overweight, Obesity, and Blood Pressure among Adolescents

We investigated the association of birthweight with overweight, obesity, and blood pressure (BP) among adolescents. This cross-sectional study included 857 participants aged 11–17 years from Liangshan, southwest China. Birthweight information was collected from the participants’ parents. The participants’ height, weight, and BP were measured. High birthweight was defined as a value greater than the sex-specific upper quartile. Participants were classified into four groups based on their weight change at birth and adolescence: normal weight at both time points, weight loss, weight gain, and high weight at both time points. High birthweight was positively associated with overweight and obesity in adolescence [odds ratio (95% confidence interval), OR (95% CI): 1.93 (1.33, 2.79)]. Compared with participants with normal weight at both time points, those with high weight at both time points were more likely to have elevated BP in adolescence (OR [95% CI]: 3.02 [1.65, 5.53]), while those with weight loss had similar odds of elevated BP. The sensitivity analysis results did not change significantly when high birthweight was defined alternatively as birthweight > 4 kg. This study showed that the association between high birthweight and elevated BP in adolescence is influenced by current weight.

Developmental Differences in Left Ventricular Strain in IUGR vs. Control Children the First Three Months of Life

BACKGROUND

Intrauterine growth restriction (IUGR) may directly affect cardiovascular function in early life. Longitudinal data on left ventricular longitudinal strain (LVLS), a key measure of cardiac function independent of body size, is not available. We hypothesize impaired cardiac function among IUGR newborns and persistence of the impairment until age 3 months.

METHOD

This is a prospective cohort study of consecutive pregnancies where IUGR was identified at 18-38 weeks gestational age (GA) with healthy controls randomly selected at 18-20 weeks GA. Echocardiograms were performed at birth and at age 3-4 months, and then compared.

RESULTS

At birth, mean (SD) LVLS did not differ between the IUGR group [N = 19; - 15.76 (3.12) %] and controls [N = 35; - 15.53 (3.56) %]. The IUGR group demonstrated no significant change in LVLS at age 3-4 months [- 17.80 (3.82) %], while the control group [- 20.91 (3.31) %] showed a significant increase (P < 0.001). Thus, LVLS was lower in the IUGR group at age 3-4 months (P = 0.003).

CONCLUSION

The lack of increase in LVLS may suggest that IUGR has a direct impact on cardiac function as early as during the first months of life. Trial registration Clinical trials.gov Identifier: NCT02583763, registration October 22, 2015. Retrospectively registered September 2014-October 2015, thereafter, registered prospectively.

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.

Exposure to Δ9-tetrahydrocannabinol during rat pregnancy leads to impaired cardiac dysfunction in postnatal life

BACKGROUND

Cannabis use in pregnancy leads to fetal growth restriction (FGR), but the long-term effects on cardiac function in the offspring are unknown, despite the fact that fetal growth deficits are associated with an increased risk of developing postnatal cardiovascular disease. We hypothesize that maternal exposure to Δ9-tetrahydrocannabinol (Δ9-THC) during pregnancy will impair fetal development, leading to cardiac dysfunction in the offspring.

METHODS

Pregnant Wistar rats were randomly selected and administered 3 mg/kg of Δ9-THC or saline as a vehicle daily via intraperitoneal injection from gestational days 6 to 22, followed by echocardiogram analysis of cardiac function on offspring at postnatal days 1 and 21. Heart tissue was harvested from the offspring at 3 weeks for molecular analysis of cardiac remodelling.

RESULTS

Exposure to Δ9-THC during pregnancy led to FGR with a significant decrease in heart-to-body weight ratios at birth. By 3 weeks, pups exhibited catch-up growth associated with significantly greater left ventricle anterior wall thickness with a decrease in cardiac output. Moreover, these Δ9-THC-exposed offsprings exhibited increased expression of collagen I and III, decreased matrix metallopeptidase-2 expression, and increased inactivation of glycogen synthase kinase-3β, all associated with cardiac remodelling.

CONCLUSIONS

Collectively, these data suggest that Δ9-THC-exposed FGR offspring undergo postnatal catch-up growth concomitant with cardiac remodelling and impaired cardiac function early in life.

IMPACT

To date, the long-term effects of perinatal Δ9-THC (the main psychoactive component) exposure on the cardiac function in the offspring remain unknown. We demonstrated, for the first time, that exposure to Δ9-THC alone during rat pregnancy results in significantly smaller hearts relative to body weight. These Δ9-THC-exposed offsprings exhibited postnatal catch-up growth concomitant with cardiac remodelling and impaired cardiac function. Given the increased popularity of cannabis use in pregnancy along with rising Δ9-THC concentrations, this study, for the first time, identifies the risk of perinatal Δ9-THC exposure on early postnatal cardiovascular health.

Adverse effects of prenatal mercury exposure on neurodevelopment during the first 3 years of life modified by early growth velocity and prenatal maternal folate level

BACKGROUND AND AIMS

Previous studies have suggested that mercury exposure and folate levels during pregnancy may influence early childhood neurodevelopment. Rapid catch-up growth in children is associated with an increased risk of pathological nervous system development. We evaluated whether the association between prenatal folate and mercury-related neuropsychological dysfunction was modified by growth velocity during childhood.

METHODS

The Mothers and Children's Environmental Health (MOCEH) birth cohort study began in 2006 and by 2010, 1751 women had been enrolled before the second trimester of their pregnancy along with their partners. Participants visited the research center at birth and 6, 12, 24, and 36 months. We measured mercury levels in maternal and cord blood and folate in maternal serum. Questionnaires to evaluate the environment and health of their child were administered and anthropometric factors including body weight and height were measured. Certified investigators used the Bayley test to measure neurobehavioral outcomes. We calculated postnatal growth change as the change in infant weight for-age z-score between birth and 3 years. Multiple linear regression and mixed models were used to examine the association between mercury exposure and children's neurodevelopment as well as the modifying effects of folate and growth velocity.

RESULTS

A total of 30.6% of children experienced rapid growth during the first 3 years of life. Median values of mercury in the low folate group were significantly higher in rapid growers (3.41 μg/L in maternal blood and 5.63 μg/L in cord blood) than in average/slow growers (3.05 μg/L in maternal blood and 5.19 μg/L in cord blood). Rapid growers were also significantly associated with decreased psychomotor development scores during the first 3 years of life and with having mothers who had low prenatal folate levels, even after adjusting for potential confounders.

CONCLUSION

Prenatal mercury exposure adversely affects infant neurodevelopment and is associated with rapid growth during the first 3 years of life. This effect was limited to children whose mothers had low prenatal folate levels, suggesting a protective effect of folate against developmental neurotoxicity due to mercury exposure and rapid catch-up growth.

Small-for-gestational-age birth is linked to cardiovascular dysfunction in early childhood

BACKGROUND

The aim of this study was to assess clinical and echographic markers of cardiovascular dysfunction in infants born small for gestational age (SGA) compared to a control group of subjects born adequate for gestational age (AGA).

METHODS

This was a single-center cross-sectional case-control study. We recruited 20 SGA and 20 gestational age-matched AGA subjects at 24 months of age. The study population underwent anthropometric and Doppler 2-dimensional echocardiographic assessments, and carotid artery intima-media thickness (cIMT) and endothelium-dependent vasodilation evaluation (FMD). The pressure-volume curve during diastole was calculated using the algorithm for the elastance calculation on 1 single beat.

RESULTS

SGA children showed lower stroke volume, lower left ventricle (LV) dimensions and volume, and greater LV thickness. Diastolic function was impaired in SGA with lower capacitance and higher elastance. Birth weight standard deviation score was positively associated with capacitance and negatively associated with E/E' ratio and elastance, and in SGA infants, the end-diastolic pressure-related volume curve was shifted to the left compared to AGA. cIMT and systemic vascular resistance were significantly higher, while FMD was lower, in SGA compared to AGA; birth weight standard deviation score was directly correlated with FMD and inversely correlated with cIMT. Finally, a longer breastfeeding duration was associated to a lower cIMT even after correction for confounding factors.

CONCLUSIONS

This study shows that infants born SGA present an early and subtle cardiovascular dysfunction compared to AGA controls. These alterations are strongly related to weight at birth. Finally, breastfeeding exerts an important protective and beneficial cardiovascular effect.

Blood Pressure Trajectories from Childhood to Adolescence in Pediatric Hypertension

It has been known for a long time that elevated blood pressure (BP) in the young may persist and progress into adult hypertension (HTN). Multiple studies have revealed the predicted BP trajectory lines starting from childhood and related them to later cardiovascular (CV) risks in adulthood. As a small baby grows into a tall adult, BP will also naturally increase. Among early-life predictors of adult HTN, birth history, such as prematurity, and low birth weight have been popular subjects in research on pediatric HTN, because body size at birth has been reported to be inversely related to the risk of adulthood HTN. The hypothesis of HTN in prematurely born adolescents has been postulated as a physiological predisposition to postnatal excessive weight gain. Current body weight is a well-known independent predictor of HTN in children, and some studies showed that children demonstrating upward crossing of their weight percentiles while growing into adolescents have significantly increased risk for elevated BP later in life. Recently, reports focused on the adverse effect of excessive catch-up growth in this population are gradually drawing attention. Accordingly, children born prematurely or with intrauterine growth restriction who show rapid changes in their weight percentile should be under surveillance with BP monitoring. Prevention of childhood obesity, along with special care for premature infants or infants small for their gestational age, by providing healthy nutritional guidelines should be cardinal strategies for the prevention of adult HTN and CV risks later in life.

Excess early postnatal weight gain and blood pressure in healthy young children

Blood pressure (BP) tracks from childhood to adulthood, and early BP trajectories predict cardiovascular disease risk later in life. Excess postnatal weight gain is associated with vascular changes early in life. However, to what extent it is associated with children's BP is largely unknown. In 853 healthy 5-year-old children of the Wheezing-Illnesses-Study-Leidsche-Rijn (WHISTLER) birth cohort, systolic (SBP) and diastolic BP (DBP) were measured, and z scores of individual weight gain rates adjusted for length gain rates were calculated using at least two weight and length measurements from birth until 3 months of age. Linear regression analyses were conducted to investigate the association between weight gain rates adjusted for length gain rates and BP adjusted for sex and ethnicity. Each standard deviation increase in weight gain rates adjusted for length gain rates was associated with 0.9 mmHg (95% CI 0.3, 1.5) higher sitting SBP after adjustment for confounders. Particularly in children in the lowest birth size decile, high excess weight gain was associated with higher sitting SBP values compared to children with low weight gain rates adjusted for length gain rates. BMI and visceral adipose tissue partly explained the association between excess weight gain and sitting SBP (β 0.5 mmHg, 95% CI -0.3, 1.3). Weight gain rates adjusted for length gain rates were not associated with supine SBP or DBP. Children with excess weight gain, properly adjusted for length gain, in the first three months of life, particularly those with a small birth size, showed higher sitting systolic BP at the age of 5 years.

Intrauterine growth restriction: impact on cardiovascular development and function throughout infancy

Intrauterine growth restriction (IUGR) refers to the situation where a fetus does not grow according to its genetic growth potential. One of the main causes of IUGR is uteroplacental vascular insufficiency. Under these circumstances of chronic oxygen and nutrient deprivation, the growth-restricted fetus often displays typical circulatory changes, which in part represent adaptations to the suboptimal intrauterine environment. These fetal adaptations aim to preserve oxygen and nutrient supply to vital organs such as the brain, the heart, and the adrenals. These prenatal circulatory adaptations are thought to lead to an altered development of the cardiovascular system and "program" the fetus for life long cardiovascular morbidities. In this review, we discuss the alterations to cardiovascular structure, function, and control that have been observed in growth-restricted fetuses, neonates, and infants following uteroplacental vascular insufficiency. We also discuss the current knowledge on early life surveillance and interventions to prevent progression into chronic disease.

Gender differences in developmental programming of cardiovascular diseases

Hypertension is a risk factor for cardiovascular disease, the leading cause of death worldwide. Although multiple factors contribute to the pathogenesis of hypertension, studies by Dr David Barker reporting an inverse relationship between birth weight and blood pressure led to the hypothesis that slow growth during fetal life increased blood pressure and the risk for cardiovascular disease in later life. It is now recognized that growth during infancy and childhood, in addition to exposure to adverse influences during fetal life, contributes to the developmental programming of increased cardiovascular risk. Numerous epidemiological studies support the link between influences during early life and later cardiovascular health; experimental models provide proof of principle and indicate that numerous mechanisms contribute to the developmental origins of chronic disease. Sex has an impact on the severity of cardiovascular risk in experimental models of developmental insult. Yet, few studies examine the influence of sex on blood pressure and cardiovascular health in low-birth weight men and women. Fewer still assess the impact of ageing on sex differences in programmed cardiovascular risk. Thus, the aim of the present review is to highlight current data about sex differences in the developmental programming of blood pressure and cardiovascular disease.

Associations between the prenatal environment and cardiovascular risk factors in adolescent girls: Internalizing and externalizing behavior symptoms as mediators

This longitudinal study examines links among adolescent internalizing and externalizing symptoms, the prenatal environment (e.g., nicotine exposure) and pre/perinatal maternal health, and cardiovascular risk factors. Girls (N=262) ages 11-17 reported internalizing and externalizing behaviors and mothers reported about the prenatal environment and maternal health during and 3 months post-pregnancy. Adolescent cardiovascular risk included adiposity, smoking, blood pressure, and salivary C-reactive protein. Internalizing symptoms mediated relations between prenatal exposures/maternal health and adiposity; externalizing symptoms mediated relations between prenatal exposures and adolescent smoking. Healthcare providers who attend to internalizing and externalizing symptoms in girls may ultimately influence cardiovascular health, especially among those with pre/perinatal risk factors.

When is birthweight at term (≥37 weeks' gestation) abnormally low? A systematic review and meta-analysis of the prognostic and predictive ability of current birthweight standards for childhood and adult outcomes

BACKGROUND

Health outcomes throughout the life course have been linked to fetal growth restriction and low birthweight. A variety of measures exist to define low birthweight, with a lack of consensus regarding which predict adverse outcome.

OBJECTIVES

To evaluate the relationship between birthweight standards and childhood and adult outcomes in term-born infants (≥37 weeks' gestation).

SEARCH STRATEGY

MEDLINE (1966-January 2011), EMBASE (1980-January 2011), and the Cochrane Library (2011:1) and MEDION were included.

SELECTION CRITERIA

Studies comprising live term-born infants (gestation ≥37 completed weeks), with weight or other anthropometric measurements recorded at birth along with childhood and adult outcomes.

DATA COLLECTION AND ANALYSIS

Data were extracted to populate 2 × 2 tables relating birthweight standard with outcome, and meta-analysis was performed where possible.

MAIN RESULTS

Fifty-nine articles (2 600 383 individuals) were selected. There was no significant relationship between birthweight <2.5 kg (odds ratio [OR] 0.98, 95% confidence intervals [CI] 0.87-1.10) and composite measure of childhood morbidity. Weight <10th centile on the population nomogram showed a small association (OR 1.49, 95% CI 1.02-2.19) for the same outcome. There was no significant association between either of the above measures and adult morbidity. The relationship between other measures and individual outcomes varied.

AUTHOR'S CONCLUSIONS

The association between low birthweight, by any definition, and childhood and adult morbidity was inconsistent. None of the current standards of low birthweight was a good predictor of adverse outcome.

Association of early childhood abdominal circumference and weight gain with blood pressure at 36 months of age: secondary analysis of data from a prospective cohort study

OBJECTIVES

To assess whether changes in measures of fat distribution and body size during early life are associated with blood pressure at 36 months of age.

DESIGN

Analysis of data collected from a prospective cohort study.

SETTING

Community-based investigation in Southampton, UK.

PARTICIPANTS

761 children with valid blood pressure measurements, born to women participating in the Southampton Women's Survey.

PRIMARY AND SECONDARY OUTCOME MEASURES

Anthropometric measurements were collected at 0, 6, 12, 24 and 36 months and conditional changes between the time points calculated. Blood pressure was measured at 36 months. Factors possibly influencing the blood pressure were assessed using linear regression. All independent variables of interest and confounding variables were included in stepwise multiple regression to identify the model that best predicted blood pressure at 36 months.

RESULTS

Greater conditional gains in abdominal circumference (AC) between 0-6 and 24-36 months were associated with higher systolic and diastolic blood pressures at 36 months (p<0.001). Subscapular skinfold and height gains were weakly associated with higher blood pressures, while greater weight gains between 0-6, 12-24 and 24-36 months were more strongly associated, but the dominant influences were AC gains, particularly from 0-6 to 24-36 months. Thus one SD score increases in AC between 0-6 and 24-36 months were associated with 1.59 mm Hg (95% CI 0.97 to 2.21) and 1.84 mm Hg (1.24 to 2.46) higher systolic blood pressures, respectively, and 1.04 mm Hg (0.57 to 1.51) and 1.02 mm Hg (0.56, 1.48) higher diastolic pressures, respectively.

CONCLUSIONS

Conditional gains in abdominal circumference, particularly within 6 months of birth and in the year preceding measurement, were more positively associated with blood pressure at 36 months than gains in other anthropometric measures. Above-average AC gains in early childhood may contribute to adult hypertension and increased cardiovascular disease risk.

Association between infancy BMI peak and body composition and blood pressure at age 5-6 years

INTRODUCTION

The development of overweight is often measured with the body mass index (BMI). During childhood the BMI curve has two characteristic points: the adiposity rebound at 6 years and the BMI peak at 9 months of age. In this study, the associations between the BMI peak and body composition measures and blood pressure at age 5-6 years were investigated.

METHODS

Measurements from the Amsterdam Born Children and their Development (ABCD) study were available for this study. Blood pressure (systolic and diastolic) and body composition measures (BMI, waist-to-height ratio, fat percentage) were gathered during a health check at about 6 years of age (n = 2822). All children had multiple BMI measurements between the 0-4 years of age. For boys and girls separately, child-specific BMI peaks were extracted from mixed effect models. Associations between the estimated BMI peak and the health check measurements were analysed with linear models. In addition, we investigated the potential use of the BMI at 9 months as a surrogate measure for the magnitude of the BMI peak.

RESULTS

After correction for the confounding effect of fetal growth, both timing and magnitude of the BMI peak were significantly and positively associated (p<0.001) with all body composition measures at the age of 5-6 years. The BMI peak showed no direct association with blood pressure at the age 5-6 year, but was mediated by the current BMI. The correlation between the magnitude of the BMI peak and BMI at 9 months was approximately 0.93 and similar associations with the measures at 5-6 years were found.

CONCLUSION

The magnitude of the BMI peak was associated with body composition measures at 5-6 years of age. Moreover, the BMI at 9 months could be used as surrogate measure for the magnitude of the BMI peak.

Birth weight and childhood blood pressure

A large body of literature suggests an inverse relationship between birth weight and blood pressure in children, adolescents and adults. The most persistent findings have been observed in children with a history of low birth weight or intrauterine growth restriction, while a large number of studies carried out in populations with normally distributed birth weight have shown conflicting results. A recently reported strong direct association between high birth weight and blood pressure, and the significant positive effect of postnatal growth on blood pressure suggests that the fetal origins of adult disease hypothesis should be expanded to include the role of excessive fetal and postnatal growth. In this paper, we review recent studies on the relationship between birth weight and blood pressure in childhood, with a focus on confounding variables that may explain the conflicting results of published work in this field.

The relationship between birth weight and blood pressure in childhood: a population-based study

BACKGROUND

Low birth weight has been associated with increased risk of hypertension later in life. The aim of this study was to evaluate the association between birth weight and blood pressure (BP) in healthy 9- to 10-year-old Icelandic children.

METHODS

Each child underwent 4 seated BP measurements, and the BP percentile was calculated from the mean of the 4 measurements. Height and weight were measured and birth weight retrieved from the Icelandic Birth Registry. Birth measures and anthropometric data were correlated with BP and BP percentiles. Multivariable linear regression was employed to examine the association between BP and birth measures.

RESULTS

Of 857 children with complete data, 445 were female (51.9%). The mean BP was 112/64 mm Hg in males and 111/63 mm Hg in females. The mean birth weight was 3714 ± 620 g. No correlation was found between birth weight and absolute BP values. A significant negative correlation between birth weight and both systolic (r = -0.09, P = 0.005) and diastolic (r = -0.08, P = 0.014) BP percentiles was observed. Gestational age did not correlate with BP.

CONCLUSION

In contrast to many previous studies, we found no association between birth weight and absolute BP in children. However, we observed a statistically significant negative correlation between birth weight and BP percentiles. The lack of standardized BP values may partly explain the conflicting results of previous studies in children, and we suggest that BP percentiles be examined more thoroughly in association with birth weight.

Is the association between ACE genes and blood pressure mediated by postnatal growth during the first 3 years?

Unlike the defined role of angiotensin-converting enzyme (ACE) gene in adult hypertension, ACE gene did not show direct influence on childhood blood pressure (BP), rather, seemed to be related to childhood growth with age-dependent characteristics. Thus, we examined intermediate effects of postnatal growth between the ACE polymorphisms and BP. We analyzed data from 257 children born in 2001-04 at Ewha Womans University Hospital in Seoul, Korea, and followed them up until 3 years of age. Children with excessive adiposity had higher BP, as rapid growers did to no-change and decelerated growers. The ACE II genotype was associated with greater growth acceleration than the DD genotype (II: 46.8% vs. DD: 23.9%), and with a higher BP. The interactions between ACE genotype and adiposity at age 3 were significant on the BP levels. The highest BP increase with the same degree of adiposity was observed in those with the II genotype [β (SE) for BMI: 1.9 (0.9), p=0.04]; particularly, only rapid grown II carriers demonstrated statistical significance on this linear association. These results suggested that ACE polymorphisms and BP association are mediated by postnatal growth. Further studies are required to determine the age-specific ACE genetic effects and its undefined biological mechanism.

Differences in association between birth parameters and blood pressure in children from preschool to high school

We aimed to investigate the association between birth parameters with blood pressure (BP) among preschool- and school-aged children. Two separate childhood datasets were used: (1) 1295 children aged 3-6 years were examined during 2007-2009; and (2) 1741 and 2353 children aged 6 and 12 years, respectively, were examined during 2004-2006. Birth parameter data were obtained from parental records. BP was measured using standard protocols. Among 6-year-old children, each 1 kg decrease in birth weight was associated with a 1.33- and 1.20-mm Hg higher systolic and diastolic BP, respectively, after multivariable adjustment. In 6-year-old children, a decrease of 1 week in gestational age was independently associated with a 0.33- and 0.37-mm Hg higher systolic and diastolic BP, respectively. Six-year-old children in the low birth weight category (≤ 2499 g) versus those in the normal/high birth weight category (≥ 2500 g) had significantly higher systolic BP (P<0.0001). Girls in the low birth weight category versus those in the normal/high weight category had higher systolic BP (P=0.02). Significant associations were not observed among preschool-aged children and preadolescents. Birth weight and gestational age were strongly associated with BP among 6-year-old children, particularly girls, but not among preschoolers or preadolescents.