Fetal growth restriction in preterm infants and cardiovascular function at five years of age

Understanding changes in echocardiographic parameters at different ages following fetal growth restriction: a systematic review and meta-analysis

Fetal growth restriction (FGR) increases cardiovascular risk by cardiac remodeling and programming. This systematic review and meta-analysis across species examines the use of echocardiography in FGR offspring at different ages. PubMed and Embase.com were searched for animal and human studies reporting on echocardiographic parameters in placental insufficiency-induced FGR offspring. We included six animal and 49 human studies. Although unable to perform a meta-analysis of animal studies because of insufficient number of studies per individual outcome, all studies showed left ventricular dysfunction. Our meta-analyses of human studies revealed a reduced left ventricular mass, interventricular septum thickness, mitral annular peak velocity, and mitral lateral early diastolic velocity at neonatal age. No echocardiographic differences during childhood were observed, although the small age range and number of studies limited these analyses. Only two studies at adult age were performed. Meta-regression on other influential factors was not possible due to underreporting. The few studies on myocardial strain analysis showed small changes in global longitudinal strain in FGR offspring. The quality of the human studies was considered low and the risk of bias in animal studies was mostly unclear. Echocardiography may offer a noninvasive tool to detect early signs of cardiovascular predisposition following FGR. Clinical implementation yet faces multiple challenges including identification of the most optimal timing and the exact relation to long-term cardiovascular function in which echocardiography alone might be limited to reflect a child's vascular status. Future research should focus on myocardial strain analysis and the combination of other (non)imaging techniques for an improved risk estimation.NEW & NOTEWORTHY Our meta-analysis revealed echocardiographic differences between fetal growth-restricted and control offspring in humans during the neonatal period: a reduced left ventricular mass and interventricular septum thickness, reduced mitral annular peak velocity, and mitral lateral early diastolic velocity. We were unable to pool echocardiographic parameters in animal studies and human adults because of an insufficient number of studies per individual outcome. The few studies on myocardial strain analysis showed small preclinical changes in FGR offspring.

Cardiac biomarkers and left ventricular systolic function in former very preterm infants and term controls at preschool age

Introduction

Due to improvements in perinatal care, survival rates of preterm infants have improved during the last decades. However, these infants remain at risk of developing cardiovascular sequelae later in life. This study aimed to investigate the cardiac biomarkers and left ventricular systolic function in former preterm infants in comparison with term controls at preschool age.

Methods

The study included children aged 5-7 years old born below 32 weeks of gestational age. The control group consisted of same-age children born at term. Basic data of study participants were collected using questionnaires and follow-up databases. During the study visit, we recorded anthropometric data and blood pressure readings, determined high-sensitive cardiac troponin T (hs-cTnT) and N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) concentrations, and calculated fractional shortening (FS) and left ventricular mass (LVM).

Results

Term-born (n = 25; median gestational age, 40.1 weeks) compared with preterm-born infants (n = 80; median gestational age 29.6 weeks) showed no significant differences in the median concentration of hs-cTnT [median, 3.5 (IQR 3.5; 3.5) vs. 3.5 (3.5; 3.5) ng/L, p = 0.328] and the median concentration of NT-pro-BNP [median, 91.0 (IQR 40.8; 150.3) vs. 87.5 (50.1; 189.5) ng/L, p = 0.087]. FS and LVM/LVMI were not significantly different between the two groups.

Conclusion

At preschool age, we observed no significant differences in cardiac biomarkers and left ventricular systolic function in preterm infants. Further studies are warranted to explore the potential of cardiac biomarkers as a prognostic tool for subclinical cardiac alterations after preterm birth.

Effect of preterm birth on blood pressure in later life: A systematic review and meta-analysis

Introduction

Preterm birth is linked to various complications in both infancy and adulthood. We assessed the association between preterm birth and hypertension in adulthood.

Materials and Methods

PubMed, EMBASE, and Cochrane CENTRAL Register were searched for randomized controlled trials (RCT) comparing systolic and diastolic blood pressures in individuals born preterm and those born full-term, from inception till April 11th, 2022. Data were extracted, pooled, and analyzed. Forest plots were created for a visual demonstration.

Results

Twenty-eight studies were included in our meta-analysis. SBP and DBP across all categories (Mean, Ambulatory, Daytime, and Nighttime) were higher in the preterm group compared to the term group. Mean SBP, mean ambulatory SBP, mean daytime SBP and mean nighttime SBP were 4.26 mmHg [95% CI: 3.09-5.43; P < 0.00001], 4.53 mmHg [95% CI: 1.82-7.24; P = 0.001], 4.51 mmHg [95% CI: 2.56-6.74; P < 0.00001], and 3.06 mmHg [95% CI: 1.32-4.80; P = 0.0006] higher in the preterm group, respectively. Mean DBP, mean ambulatory DBP, mean daytime DBP, and mean nighttime DBP were 2.32 mmHg [95% CI: 1.35-3.29; P < 0.00001], 1.54 mmHg [95% CI 0.68-2.39; P = 0.0004], 1.74 mmHg [95% CI: 0.92-2.56; P < 0.0001], and 1.58 mmHg [95% CI: 0.34-2.81; P = 0.01] higher in the preterm group, respectively.

Conclusion

Our observations suggest that individuals who were born preterm may have higher blood pressures as compared to those who were born full-term.

Small for gestational age preterm infants and later adiposity and height: A systematic review and meta-analysis

BACKGROUND

Overweight and obesity and their consequent morbidities are important worldwide health problems. Some research suggests excess adiposity origins may begin in fetal life, but unknown is whether this applies to infants born preterm.

OBJECTIVE

The objective of the study was to assess the association between small for gestational age (SGA) birth and later adiposity and height among those born preterm.

DATA SOURCES

MEDLINE, EMBASE and CINAHL until October 2022.

STUDY SELECTION AND DATA EXTRACTION

Studies were included if they reported anthropometric (adiposity measures and height) outcomes for participants born preterm with SGA versus non-SGA. Screening, data extraction and risks of bias assessments were conducted in duplicate by two reviewers.

SYNTHESIS

We meta-analysed across studies using random-effects models and explored potential heterogeneity sources.

RESULTS

Thirty-nine studies met the inclusion criteria. In later life, preterm SGA infants had a lower body mass index (-0.66 kg/m2 , 95% CI -0.79, -0.53; 32 studies, I2  = 16.7, n = 30,346), waist circumference (-1.20 cm, 95% CI -2.17, -0.23; 13 studies, I2  = 19.4, n = 2061), lean mass (-2.62 kg, 95% CI -3.45, 1.80; 7 studies, I2  = 0, n = 205) and height (-3.85 cm, 95% CI -4.73, -2.96; 26 studies, I2  = 52.6, n = 4174) compared with those preterm infants born non-SGA. There were no differences between preterm SGA and preterm non-SGA groups in waist/hip ratio, body fat, body fat per cent, truncal fat per cent, fat mass index or lean mass index, although power was limited for some analyses. Studies were rated at high risk of bias due to potential residual confounding and low risk of bias in other domains.

CONCLUSIONS

Compared to their preterm non-SGA peers, preterm infants born SGA have lower BMI, waist circumference, lean body mass and height in later life. No differences in adiposity were observed between SGA preterm infants and non-SGA preterm infants.

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.

Small for date preterm infants and risk of higher blood pressure in later life: A systematic review and meta-analysis

BACKGROUND

Historical reports suggest that infants born small for gestational age (SGA) are at increased risk for high blood pressure (BP) at older ages after adjustment for later age body size. Such adjustment may be inappropriate since adiposity is a known cause of cardiovascular and metabolic disease.

OBJECTIVES

To assess the association between SGA births and later BP among preterm births, considering potential background confounders and over-adjustment for later body size.

METHODS

A database search of studies up to October 2022 included MEDLINE, EMBASE and CINAHL. Studies were included if they reported BP (systolic [SBP] or diastolic [DBP]) (outcomes) for participants born preterm with SGA (exposure) or non-SGA births. All screening, extraction steps, and risk of bias (using the Risk of Bias In Non-randomised Studies of Interventions [ROBINS-I] tool) were conducted in duplicate by two reviewers. Data were pooled in meta-analysis using random-effects models. We explored potential sources of heterogeneity.

RESULTS

We found no meaningful difference in later BP between preterm infants with and without SGA status at birth. Meta-analysis of 25 studies showed that preterm SGA, compared to preterm non-SGA, was not associated with higher BP at age 2 and older with mean differences for SBP 0.01 mmHg (95% CI -0.10, 0.12, I²  = 59.8%, n = 20,462) and DBP 0.01 mm Hg (95% CI -0.10, 0.12), 22 studies, (I²  = 53.0%, n = 20,182). Adjustment for current weight did not alter the results, which could be due to the lack of differences in later weight status in most of the included studies. The included studies were rated to be at risk of bias due to potential residual confounding, with a low risk of bias in other domains.

CONCLUSIONS

Evidence indicates that preterm infants born SGA are not at increased risk of developing higher BP as children or as adults as compared to non-SGA preterm infants.

Subclinical Changes in Left Heart Structure and Function at Preschool Age in Very Low Birth Weight Preterm Infants

Background

Survivors of preterm birth are at risk of long-term cardiovascular consequences. The objective of this prospective observational study was to assess left heart function at preschool age in preterm children with very low birth weight (VLBW).

Methods

We recruited children aged 5–6 years from preterm infants and full-term children. All subjects underwent conventional echocardiography and speckle-tracking echocardiography. The results were compared between the preterm and term groups.

Results

Eighty-seven VLBW preterm children and 29 term controls were included in the study. After adjusting for body surface area, the preterm group compared to the full-term group had significantly smaller left ventricular (LV) end-diastolic and end-systolic internal dimensions (31.2 vs. 33.5 mm, p = 0.048; and 20.0 vs. 21.6 mm, respectively; p = 0.024), lower LV end-diastolic and end-systolic volumes (38.8 vs. 46.3 mL, p = 0.024; and 12.8 vs. 15.6 mL, respectively; p = 0.008). Left atrial (LA) maximal and minimal volume were also significantly smaller in the preterm group (15.4 vs. 18.9 mL, p = 0.017; and 6.2 vs 7.5 mL, respectively; p = 0.018). LV global longitudinal strain (−21.4 vs. −23.2%, p < 0.0001) and systolic strain rate (−1.30 vs. −1.37 /s, p = 0.001) were significantly lower in the preterm group than in the term control group. LA longitudinal strain was decreased (43.9 vs. 52.8%, p < 0.0001) and left atrial stiffness index (0.17 vs. 0.14, p < 0.0001) was increased in preterm infants. However, all the measurements in both groups were within normal range.

Conclusions

Subclinical changes of left heart structure and function were found in VLBW infants at preschool age. Additional long-term follow-ups of the cardiovascular outcomes are needed in this vulnerable population.

Effect of Preterm Birth on Cardiac and Cardiomyocyte Growth and the Consequences of Antenatal and Postnatal Glucocorticoid Treatment

Preterm birth coincides with a key developmental window of cardiac growth and maturation, and thus has the potential to influence long-term cardiac function. Individuals born preterm have structural cardiac remodelling and altered cardiac growth and function by early adulthood. The evidence linking preterm birth and cardiovascular disease in later life is mounting. Advances in the perinatal care of preterm infants, such as glucocorticoid therapy, have improved survival rates, but at what cost? This review highlights the short-term and long-term impact of preterm birth on the structure and function of the heart and focuses on the impact of antenatal and postnatal glucocorticoid treatment on the immature preterm heart.

Preterm Birth With Neonatal Interventions Accelerates Collagen Deposition in the Left Ventricle of Lambs Without Affecting Cardiomyocyte Development

Background

Adults born preterm (< 37 weeks’ gestation) exhibit altered cardiac growth and are susceptible to cardiac dysfunction. Sheep studies have shown that moderate preterm birth results in maladaptive structural remodelling of the cardiac ventricles. The aim of this study was to examine ventricular structure in lambs born at a greater severity of preterm birth and ventilated postnatally.

Methods

Former-preterm lambs delivered at 128 days’ gestation, and mechanically ventilated for a week after birth, were compared with unventilated lambs born at term (150 days’ gestation), at 2 months (term: n = 10, former-preterm: n = 8), and 5 months (term: n = 9, former-preterm: n = 8) term-equivalent age. The right ventricle and left ventricle plus septum were analysed using immunohistochemistry, histology, and stereology.

Results

Cardiomyocyte number, cross-sectional area, proliferation, and apoptosis were not affected by preterm birth or age. Left ventricle plus septum interstitial collagen levels increased with age (P = 0.0015) and were exacerbated by preterm birth (P = 0.0006; 2 months term: 0.57% ± 0.07%, former-preterm: 1.44% ± 0.18%; 5 months term: 1.37% ± 0.25%, former-preterm: 2.15% ± 0.31%). Right ventricle interstitial collagen levels increased with age (P = 0.012) but were not affected by preterm birth.

Conclusion

This study is the first to explore the effect of preterm birth combined with modern neonatal interventions on the ventricular myocardium in lambs. There was no adverse impact on cardiomyocyte growth in early postnatal life. Of concern, however, there was increased collagen deposition in the preterm hearts, which has the potential to induce cardiac dysfunction, especially if it becomes exaggerated with ageing.

Left Ventricle Structure and Function in Young Adults Born Very Preterm and Association with Neonatal Characteristics

Preterm birth increases risk of cardiovascular disease and early death. A body of evidence suggests left ventricle (LV) echocardiographic alterations in children and adults born preterm. We aimed to determine if neonatal characteristics were associated with alterations in LV structure and function in preterm adults. We evaluated a cohort of 86 young adults born preterm below 30 weeks of gestation, and 85 full-term controls. We determined LV dimensions and function using tissue Doppler imaging, conventional and speckle tracking echocardiography (STE). Adults born preterm had smaller LV dimensions, but these differences did not remain after adjustment for body surface area (BSA), which was smaller in the preterm group. Stroke volume and cardiac output were reduced even after adjustment for BSA. We found a smaller e’ wave in the preterm group, but other markers of systolic and diastolic function did not differ. Use of antenatal steroids may be associated with a further reduced cardiac output in those born preterm. Adults born preterm show alterations in markers of LV dimensions and function. Identification of these markers may represent opportunities for early prevention of cardiovascular events in this at-risk population.

Cardiac and vascular health in late preterm infants

Adults who were born preterm are at increased risk of hypertension and cardiovascular disease in later life. Infants born late preterm are the majority of preterm births; however, the effect of late preterm on risk of cardiovascular disease is unclear. The objective of this study was to assess whether vascular health and cardiac autonomic control differ in a group of late preterm newborn infants compared to a group of term-born infants.A total of 35 healthy late preterm newborn infants, with normal growth (34-36 completed weeks' gestation) and 139 term-born infants (37-42 weeks' gestation) were compared in this study. Aortic wall thickening, assessed as aortic intima-media thickness (IMT) by high-resolution ultrasound, and cardiac autonomic control, assessed by heart rate variability, were measured during the first week of life. Postnatal age of full-term and late preterm infants at the time of the study was 5 days (standard deviation [SD] 5) and 4 days (SD 3), respectively.Infants born late preterm show reduced aortic IMT (574 μm [SD 51] vs. 612 μm [SD 73]) and reduced heart rate variability [log total power 622.3 (606.5) ms2 vs. 1180. 6 (1114.3) ms2], compared to term infants. These associations remained even after adjustment for sex and birth weight.Infants born late preterm show selective differences in markers of cardiovascular risk, with potentially beneficial differences in aortic wall thickness in contrast to potentially detrimental differences in autonomic control, when compared with term-born control infants. These findings provide pathophysiologic evidence to support an increased risk of hypertension and sudden cardiac death in individuals born late preterm.

Cardiovascular risk factors in those born preterm - systematic review and meta-analysis

Emerging evidence demonstrates a link between preterm birth (PTB) and later life cardiovascular disease (CVD). We conducted a systematic review and meta-analysis to compare conventional CVD risk factors between those born preterm and at term. PubMed, CINAHL, SCOPUS, and EMBASE databases were searched. The review protocol is registered in PROSPERO (CRD42018095005). CVD risk factors including systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index, lipid profile, blood glucose, and fasting insulin among those born preterm (<37 weeks' gestation) were compared with those born at term (≥37 weeks' gestation). Subgroup analyses based on gender, age, gestational at birth (<32 weeks' gestation and <28 weeks' gestation), and PTB associated with small for gestational age or average for gestational age were also performed. Fifty-six studies provided data on 308,987 individuals. Being born preterm was associated with 3.26 mmHg (95% confidence interval [CI] 2.08 to 4.44) higher mean SBP and 1.32 mmHg (95% CI: 0.61 to 2.04) higher mean DBP compared to being born at term. Subgroup analyses demonstrated that SBP was higher among (a) preterm compared to term groups from early adolescence until adulthood; (b) females born preterm but not among males born preterm compared to term controls; and (c) those born at <32 weeks or <28 weeks compared to term. Our meta-analyses demonstrate higher SBP and DBP among those born preterm compared to term. The difference in SBP is evident from early adolescence until adulthood.

Preterm Birth Is a Novel, Independent Risk Factor for Altered Cardiac Remodeling and Early Heart Failure: Is it Time for a New Cardiomyopathy?

PURPOSE OF REVIEW

Around 10% of the global population is born preterm (< 37 weeks' gestation). Preterm birth is associated with an increased risk of cardiovascular events, with preterm-born individuals demonstrating a distinct cardiac phenotype. This review aims to summarize the main phenotypic features of the preterm heart and directions for future research to develop novel intervention strategies.

RECENT FINDINGS

Being born between 28 and 31 weeks' gestation results in a 4-fold higher risk of heart failure in childhood and adolescence and 17-fold increased risk when born less than 28 weeks' gestation. In support of this being due to a reduction in myocardial functional reserve, preterm-born young adults have an impaired left ventricular cardiac systolic response to moderate and high intensity physiological stress, despite having a preserved resting left ventricular ejection fraction. Similar impairments under physiological stress were also recently reported regarding the right ventricle in young adults born preterm. Preterm birth relates to a unique cardiac phenotype with an impaired response to stress conditions. These data, combined with the work in animal models, suggest that being born preterm may lead to a novel form of cardiomyopathy. Understanding the driving mechanisms leading to this unique cardiac phenotype is important to reduce risk of future heart failure and cardiovascular events.

The Preterm Heart in Childhood: Left Ventricular Structure, Geometry, and Function Assessed by Echocardiography in 6-Year-Old Survivors of Periviable Births

BACKGROUND

Preterm birth has been associated with increased risk of cardiovascular morbidity in adult life. We evaluated whether preterm birth is associated with deviating cardiac structure and function before school start.

METHODS AND RESULTS

In total, 176 children aged 6 years and born extremely preterm (EXPT; gestational age of 22-26 weeks) and 134 children born at term (control [CTRL]) were studied. We used echocardiography to assess left heart dimensions, geometry, and functions. Recording and off-line analyses of echocardiographic images were performed by operators blinded to group belonging. Body size, blood pressure, and heart rate were also measured. Rates of family history of cardiovascular disease and sex distribution were similar in the EXPT and CTRL groups. Heart rate and systolic blood pressure did not differ, whereas diastolic blood pressure was slightly higher in EXPT than CTRL participants. After adjusting for body surface area, left ventricular length, width, and aortic valve annulus diameter were 3% to 5% smaller in EXPT than CTRL participants. Left ventricular longitudinal shortening and systolic tissue velocity were 7% to 11% lower, and transversal shortening fraction was 6% higher in EXPT than CTRL participants. The EXPT group also exhibited lower atrial emptying velocities than the CTRL group. Sex, fetal growth restriction, or a patent ductus arteriosus in the neonatal period did not contribute to cardiac dimensions or performance.

CONCLUSIONS

Six-year-old children born extremely preterm exhibit a unique cardiac phenotype characterized by smaller left ventricles with altered systolic and diastolic functions than same-aged children born at term.

Disproportionate cardiac hypertrophy during early postnatal development in infants born preterm

BackgroundAdults born very preterm have increased cardiac mass and reduced function. We investigated whether a hypertrophic phenomenon occurs in later preterm infants and when this occurs during early development.MethodsCardiac ultrasound was performed on 392 infants (33% preterm at mean gestation 34±2 weeks). Scans were performed during fetal development in 137, at birth and 3 months of postnatal age in 200, and during both fetal and postnatal development in 55. Cardiac morphology and function was quantified and computational models created to identify geometric changes.ResultsAt birth, preterm offspring had reduced cardiac mass and volume relative to body size with a more globular heart. By 3 months, ventricular shape had normalized but both left and right ventricular mass relative to body size were significantly higher than expected for postmenstrual age (left 57.8±41.9 vs. 27.3±29.4%, P<0.001; right 39.3±38.1 vs. 16.6±40.8, P=0.002). Greater changes were associated with lower gestational age at birth (left P<0.001; right P=0.001).ConclusionPreterm offspring, including those born in late gestation, have a disproportionate increase in ventricular mass from birth up to 3 months of postnatal age. These differences were not present before birth. Early postnatal development may provide a window for interventions relevant to long-term cardiovascular health.

Normative Left Ventricular M-Mode Echocardiographic Values in Preterm Infants up to 2 kg

BACKGROUND

There is a paucity of normative echocardiographic data in preterm infants. The objectives of this study were to (1) derive left ventricular (LV) M-mode reference values and (2) compare the performance of alternative methods of indexing LV dimensions and LV mass (LVM) in preterm infants. The authors propose that indexing LV measures to weight in preterm infants is a practical approach given the variability associated with tape-measure length measurement in infants.

METHODS

In this retrospective study, LV M-mode echocardiographic measurements of end-diastolic interventricular septal thickness, end-diastolic LV posterior wall thickness, LV end-diastolic and end-systolic dimensions, LVM, and relative wall thickness were remeasured in 503 hospitalized preterm infants ≤2 kg (372 from a retrospective sample and 131 prospectively enrolled). Measures for all variables did not differ between retrospective and prospective samples, so results were pooled. LV dimensions and LVM indexed for weight, length, and body surface area sex-specific centile curves and corresponding Z scores were generated using Cole's lambda-mu-sigma method. Threshold limits (10th and 80th percentiles) were used to generate the normative range for relative wall thickness.

RESULTS

Sex-specific centile curves using LVM, end-diastolic interventricular septal thickness, end-diastolic LV posterior wall thickness, LV end-diastolic dimension, and LV end-systolic dimension indexed to weight were similar to the curves generated using length and body surface area. The mean normal range for relative wall thickness was 0.33 (10th percentile, 0.26; 80th percentile, 0.38).

CONCLUSIONS

From this large cohort of preterm infants, LV M-mode dimension and LVM centile curves indexed to weight were developed as a practical method to assess LV morphology in preterm infants.

Long-Term Impact of Preterm Birth: Neurodevelopmental and Physical Health Outcomes

Preterm birth severely disrupts the normal developmental maturation of organ systems, resulting in lasting adverse effects. High blood pressure, cardiac dysfunction, obstructive lung disease, elevated blood glucose, and mental health problems occur earlier and at higher rates in the preterm-born than in the term populations. Disadvantageous health conditions may have a significant impact on the well-being of preterm-born individuals from childhood through adulthood. This review summarizes the impact of preterm birth on neurodevelopment and on cardiovascular, renal, metabolic, and pulmonary health.

Left ventricular dimensions, systolic functions, and mass in term neonates with symmetric and asymmetric intrauterine growth restriction

BACKGROUND

Previous studies have demonstrated structural changes in the heart and cardiac dysfunction in foetuses with intrauterine growth restriction. There are no available data that evaluated left ventricular dimensions and mass in neonates with symmetric and asymmetric intrauterine growth restriction. Therefore, we aimed to evaluate left ventricular dimensions, systolic functions, and mass in neonates with symmetric and asymmetric intrauterine growth restriction. We also assessed associated maternal risk factors, and compared results with healthy appropriate for gestational age neonates.

METHODS

In all, 62 asymmetric intrauterine growth restriction neonates, 39 symmetric intrauterine growth restriction neonates, and 50 healthy appropriate for gestational age neonates were evaluated by transthoracic echocardiography.

RESULTS

The asymmetric intrauterine growth restriction group had significantly lower left ventricular end-systolic and end-diastolic diameters and posterior wall diameter in systole and diastole than the control group. The symmetric intrauterine growth restriction group had significantly lower left ventricular end-diastolic diameter than the control group. All left ventricular dimensions were lower in the asymmetric intrauterine growth restriction neonates compared with symmetric intrauterine growth restriction neonates (p>0.05), but not statistically significant except left ventricular posterior wall diameter in diastole (3.08±0.83 mm versus 3.54 ±0.72 mm) (p<0.05). Both symmetric and asymmetric intrauterine growth restriction groups had significantly lower relative posterior wall thickness (0.54±0.19 versus 0.48±0.13 versus 0.8±0.12), left ventricular mass (9.8±4.3 g versus 8.9±3.4 g versus 22.2±5.7 g), and left ventricular mass index (63.6±29.1 g/m2 versus 54.5±24.4 g/m2 versus 109±28.8 g/m2) when compared with the control group.

CONCLUSIONS

Our study has demonstrated that although neonates with both symmetric and asymmetric intrauterine growth restriction had lower left ventricular dimensions, relative posterior wall thickness, left ventricular mass, and mass index when compared with appropriate for gestational age neonates, left ventricular systolic functions were found to be preserved. In our study, low socio-economic level, short maternal stature, and low maternal weight were found to be risk factors to develop intrauterine growth restriction. To our knowledge, our study is the first to evaluate left ventricular dimensions, wall thicknesses, mass, and systolic functions in neonates with intrauterine growth restriction and compare results with respect to asymmetric or symmetric subgroups.

Preeclampsia, prematurity and cardiovascular health in adult life

Investigations into how perinatal growth and intrauterine environment may 'programme' risk of later cardiovascular disease have been ongoing for over two decades. One of the more recent outcomes of these studies is the observation that certain pregnancy-related conditions, such as preterm birth, have an unusually large impact on the long-term cardiovascular health of the offspring. In the present paper, we review the current literature of how preterm birth affects the long-term cardiovascular structure and function of the offspring, considering three major areas of investigation: firstly, outlining the long-term cardiovascular phenotypic changes in preterm-born individuals; secondly, investigating factors related to preterm birth that may be modifying cardiovascular phenotype, such as preeclampsia, perinatal interventions, and physiological disturbances; and thirdly, the expected clinical relevance of these cardiovascular changes. This review discusses the importance of continued research focused on the mechanistic understanding of these cardiovascular alterations in order to develop specific primary prevention strategies.

Higher systolic blood pressure with normal vascular function measurements in preterm-born children

Preterm birth, low birth weight and poor foetal nutrition have been linked to cardiovascular disease, but the underlying mechanisms remain unclear. We explored prematurity and vascular function by studying a UK cohort of 14 049 children and conducting a systematic review.

CONCLUSION

Systolic blood pressure was higher in subjects born preterm than term, but there were no differences in endothelial dysfunction or arterial stiffness. The systematic review revealed no clear association between prematurity and vascular function.

Maternal dietary docosahexaenoic acid supplementation attenuates fetal growth restriction and enhances pulmonary function in a newborn mouse model of perinatal inflammation

The preterm infant is often exposed to maternal and neonatal inflammatory stimuli and is born with immature lungs, resulting in a need for oxygen therapy. Nutritional intervention with docosahexaenoic acid (DHA; 6.3 g/kg of diet) has been shown to attenuate inflammation in various human diseases. Previous studies demonstrated that maternal DHA supplementation during late gestation and lactation attenuated hyperoxic lung injury in newborn mouse pups. In the present studies, we tested the hypothesis that DHA supplementation to the dam would reduce hyperoxic lung injury and growth deficits in a more severe model of systemic maternal inflammation, including lipopolysaccharide (LPS) and neonatal hyperoxia exposure. On embryonic day 16, dams were placed on DHA (6.3 g DHA/kg diet) or control diets and injected with saline or LPS. Diets were maintained through weaning. At birth, pups were placed in room air or hyperoxia for 14 d. Improvements in birth weight (P < 0.01), alveolarization (P ≤ 0.01), and pulmonary function (P ≤ 0.03) at 2 and 8 wk of age were observed in pups exposed to perinatal inflammation and born to DHA-supplemented dams compared with control diet-exposed pups. These improvements were associated with decreases in tissue macrophage numbers (P < 0.01), monocyte chemoattractant protein-1 expression (P ≤ 0.05), and decreases in soluble receptor for advanced glycation end products concentrations (P < 0.01) at 2 and 8 wk. Furthermore, DHA supplementation attenuated pulmonary fibrosis, which was associated with the reduction of matrix metalloproteinases 2, 3, and 8 (P ≤ 0.03) and collagen mRNA (P ≤ 0.05), and decreased collagen (P < 0.01) and vimentin (P ≤ 0.03) protein concentrations. In a model of severe inflammation, maternal DHA supplementation lessened inflammation and improved lung growth in the offspring. Maternal supplementation with DHA may be a therapeutic strategy to reduce neonatal inflammation.

Long term cardiovascular consequences of chronic lung disease of prematurity

Pulmonary arterial (PA) hypertension in preterm infant is an important consequence of chronic lung disease of prematurity (CLD) arising mainly due to impaired alveolar development and dysregulated angiogenesis of the pulmonary circulation. Although PA pressure and resistance in these children normalise by school age, their pulmonary vasculature remains hyper-reactive to hypoxia until early childhood. Furthermore, there is evidence that systemic blood pressure in preterm born children with or without CLD is mildly increased at school age and in young adulthood when compared to term-born children. Arterial stiffness may be increased in CLD survivors due to increased smooth muscle tone of the pre-resistance and resistance vessels rather than the loss of elasticity in the large arteries. This review explores the long term effects of CLD on the pulmonary and systemic circulations along with their clinical correlates and therapeutic approaches.

Transient neonatal high oxygen exposure leads to early adult cardiac dysfunction, remodeling, and activation of the renin-angiotensin system

Perinatal conditions (such as preterm birth) can affect adult health and disease, particularly the cardiovascular system. Transient neonatal high O(2) exposure in rat in adulthood (a model of preterm birth-related complications) leads to elevated blood pressure, vascular rigidity, and dysfunction with renin-angiotensin system activation. We postulate that neonatal hyperoxic stress also affects myocardial structure, function, and expression of renin-angiotensin system components. Sprague-Dawley pups were kept with their mother in 80% O(2) or in room air (control) from days 3 to 10 of life. Left ventricular function was assessed in 4-, 7-, 12-week-old (echocardiography) and in 16-week-old (intraventricular catheterization) male O(2)-exposed versus control rats. At 16 weeks, hearts from O(2)-exposed rats showed cardiomyocyte hypertrophy, enhanced fibrosis, and increased expression of transforming growth factor-β1, senescence-associated proteins p53 and Rb, upregulation of angiotensin II type 1 (AT1) receptor expression (protein and AT1a/b mRNA), and downregulation of AT2 receptors. At 4 weeks (before blood pressure increase), the expression of cardiomyocyte surface area, fibrosis, p53, and AT1b was significantly increased and AT2 decreased in O(2)-exposed animals. After 4 weeks of continuous angiotensin II infusion (starting at 12 weeks), O(2)-exposed rats developed severe heart failure, with impaired myocardial mechanical properties compared with saline-infused rats. Transient neonatal O(2) exposure in rats leads to left ventricular hypertrophy, fibrosis and dysfunction, and increased susceptibility to heart failure under pressure overload. These results are relevant to the growing population of individuals born preterm who may be at higher risk of cardiac dysfunction when faced with increased peripheral resistance associated with hypertension, vascular diseases, and aging.

Cardiovascular function in children born very preterm after intrauterine growth restriction with severely abnormal umbilical artery blood flow

AIMS

Low birthweight has been linked to increased cardiovascular risk in adulthood. We evaluated the effect on cardiovascular outcome of intrauterine growth restriction (IUGR) with abnormal fetal blood flow in children born very preterm.

METHODS

Blood pressure, cardiac function and size, diameters, distensibility, and stiffness of the abdominal aorta, carotid, and popliteal arteries, and endothelial function were assessed non-invasively in 7-year-old children (n = 32) born very preterm with IUGR, with birthweight (median, range) 650 g (395-976 g) and gestational age 27 weeks (24-29 weeks). In addition, intima-media thickness was measured in the carotid artery. Controls were matched for gender and age and had birthweight appropriate-for-gestational-age (AGA). The study included 32 preterm-AGA children with birthweight 1010 g (660-1790) g and 32 term-AGA children with birthweight 3530 g (3000-4390) g.

RESULTS

Preterm-IUGR children had lower microvascular response to acetylcholine, lower aortic stiffness, and higher distensibility compared with the preterm-AGA group (p = 0.019, p = 0.001, and p < 0.001, respectively) and lower carotid intima-media thickness compared with the term-AGA group (p = 0.047). The highest aortic β and lowest distensibility were found in the preterm-AGA group. Height-adjusted systolic blood pressure was higher in the preterm groups than in the term-AGA group (p = 0.018). Cardiac function and size did not differ between the groups.

CONCLUSION

IUGR and preterm birth appear to be associated with structural changes in the arterial wall, whereas preterm birth seems to be associated with higher blood pressure. Using conventional echocardiography, we observed no effect of IUGR on cardiac size and function.

Feeding preterm infants today for later metabolic and cardiovascular outcomes

Preterm birth continues to contribute disproportionately to neonatal morbidity and subsequent physical and neurodevelopmental disabilities. Epidemiologic studies have described additional long-term health consequences of preterm birth such as an increased risk of hypertension and insulin resistance in adult life. It is not known whether the influence of infant and childhood growth rates and early nutrition on long-term outcomes is the same or different among preterm infants and neonates with intrauterine growth restriction. Our goal is to review the effects of fetal growth, postnatal growth, and early nutrition on long-term cardiovascular and metabolic outcomes in preterm infants. Present evidence suggests that even brief periods of relative undernutrition during a sensitive period of development have significant adverse effects on later development. Our review suggests that growth between birth and expected term and 12-18 months post-term has no significant effect on later blood pressure and metabolic syndrome, whereas reduced growth during hospitalization significantly impacts later neurodevelopment. In contrast, growth during late infancy and childhood appears to be a major determinant of later metabolic and cardiovascular well being, which suggests that nutritional interventions during this period are worthy of more study. Our review also highlights the paucity of well-designed, controlled studies in preterm infants of the effects of nutrition during hospitalization and after discharge on development, the risk of developing hypertension, or insulin resistance.

Cardiovascular function in adulthood following intrauterine growth restriction with abnormal fetal blood flow

OBJECTIVES

To examine whether intrauterine growth restriction (IUGR) is associated with increased cardiovascular risk later in life.

METHODS

We examined 19 young adults (aged 22-25 years) who were born at term after IUGR, along with 18 controls. All had been examined previously with fetal Doppler, and in the present follow-up with echocardiography, carotid echo-tracking ultrasound, applanation tonometry, blood pressure and laser Doppler, in order to characterize their cardiac and vascular geometry and/or function.

RESULTS

The diameter of the ascending aorta and the left ventricular diameter were smaller in the IUGR group, but only ascending aortic diameter remained significantly smaller after adjustment for body surface area (P < 0.05). The aortic pressure augmentation index was higher in the IUGR group (P < 0.05). The common carotid artery diameter, intima-media thickness and distensibility as well as left ventricular mass and function were similar in the two groups. IUGR status was found to be an independent predictor of ascending aortic diameter.

CONCLUSIONS

IUGR due to placental dysfunction seems to contribute to the higher systolic blood pressure augmentation and the smaller aortic dimensions that are observed in adults more than 20 years later, with possible negative consequences for future left ventricular performance due to increased aortic impedance.

From a regional cohort of extremely low birth weight infants: cardiac function at the age of 7 years

BACKGROUND

The long-term impact of prematurity on cardiac structure and function has not yet been fully discovered.

OBJECTIVES

To assess long-term cardiac complications in the regional cohort of extremely low birth weight (ELBW) children born in 2002-2004.

MATERIAL AND METHODS

Eighty-one children born as ELBW infants (91% of the available cohort) with a median birth weight of 890 g (25-75th percentile: 760-950) were evaluated at the mean age of 6.7 years. The control group included 40 children born full-term, selected from one general practice in the district. Echocardiography and 24-hour ambulatory blood pressure measurements (ABPM) were performed. The primary outcome variable was the presence of cardiac complications such as left ventricular hypertrophy (LVH), diastolic dysfunction or systolic dysfunction.

RESULTS

LVH was diagnosed in 4/81 ELBW children and 2/40 control children (p = 1.0). Concentric remodeling was detected in 8 (10%) subjects from the ELBW group and in 2 (5%) from the control group (p = 0.49). There were no patients with diastolic or systolic dysfunction in either group. After having expressed the results of M-mode echocardiography as z-scores for body surface area (BSA), statistically significant differences were observed for right-ventricle dimension in diastole (-1.49 ± 1.25 vs. -0.31 ± 0.91; p < 0.001), LV inner dimension in diastole (-0.53 ± 1.26 vs. 0.13 ± 0.94; p = 0.01) and left atrium (-0.93 ± 1.07 vs. -0.15 ± 1.02; p < 0.01). Heart rate (HR) was significantly faster in ELBW children (92.9 ± 8.4 vs. 86.7 ± 7.4 bpm; p = 0.01 adjusted for BSA) and they also had significantly higher night-time blood pressure [mean (z-score): 1.15 vs. 0.2; p = 0.02] without nocturnal dipping (night-time dipping <10%: 13 (16.7%) vs. 2 (5.2%), p = 0.13).

CONCLUSIONS

No differences were found between the groups in the occurrence of cardiac complications. Ex-preterm ELBW children at age 6 may have a faster HR, smaller cardiac dimensions on echocardiography and higher nocturnal blood pressure. The clinical relevance of these findings is unknown.

Evaluation of cardiac functions in term small for gestational age newborns with mild growth retardation: a serial conventional and tissue Doppler imaging echocardiographic study

BACKGROUND

The aim of this study is to evaluate the cardiac functions of term small for gestational age (SGA) babies with mild growth retardation by echocardiography during the postnatal period.

METHODS AND RESULTS

Thirty term SGA (2271±207 g/38-41 weeks (mean 39.5 weeks)) and 30 term AGA (3298±338 g/38-41 weeks (mean 39 weeks)) newborns as the control group, with normal general health status and with no nutritional problems were evaluated at three time points, on the 3rd postnatal day, at the 3rd and the 6th months. In the initial analysis, heart rate, left ventricular end diastolic diameter index (LVEdDI), cardiac index (CI), all E/A, Em/Am and E/Em ratios, pulsed wave Doppler myocardial performance index (MPI), and tissue Doppler imaging MPI values were higher in SGA babies than the control group. In the last analysis, only heart rate, LVEdDI and CI values were different between SGA and control groups.

CONCLUSIONS

Systolic and diastolic cardiac dysfunctions were determined in SGA babies with mild growth retardation during the first 6 months of postnatal period. Any disease that affects the hemodynamic stability of these patients during postnatal period may lead to early progressive deterioration in cardiac functions. Furthermore, many of the cardiac functions of these babies have been improved about the 6th month period, and high levels of heart rate and LVEdDI may be suggested as an indicator of cardiac remodeling.

Risk of hypertension among young adults who were born preterm: a Swedish national study of 636,000 births

Previous studies have reported an association between preterm birth and elevated blood pressure in adolescence and young adulthood. These studies were based on single-day blood pressure measurements and had limited ability to estimate risk of hypertension measured over a longer period and across the full range of gestational ages. The authors conducted a national cohort study of all infants born in Sweden from 1973 through 1979 (n = 636,552), including 28,220 born preterm (<37 weeks), followed to ages 25.5-37.0 years to determine whether individuals born preterm were more likely to be prescribed antihypertensive medications in 2005-2009 than those born full term. Antihypertensive medication data were obtained from all outpatient and inpatient pharmacies throughout Sweden. Young adults who were born preterm had an increased relative rate of antihypertensive medication prescription that increased monotonically by earlier gestational age and that was independent of fetal growth. The adjusted odds ratio for ≥1 antihypertensive medications/year ranged from 1.25 (95% confidence interval: 1.12, 1.39) for those born near term (35-36 weeks) to 2.51 (95% confidence interval: 1.11, 5.68) for those born extremely preterm (23-27 weeks) relative to those born full term. These findings suggest that preterm birth is strongly associated with hypertension in young adulthood, including an increased risk among those born near term.

Intima-media thickness and flow-mediated dilatation in the Helsinki study of very low birth weight adults

BACKGROUND

Adults born at a very low birth weight (VLBW) (< 1500 g), compared with those born at term, bear risk factors for cardiovascular disease, including higher blood pressure and insulin resistance.

OBJECTIVE

We studied, in young adults born at a VLBW, early signs of an accelerated atherosclerotic process and the relationship of these signs with postnatal growth.

METHODS

We compared 92 with a VLBW with 68 who were born at term. At age 18 to 27, we measured stiffness and intima-media thickness (IMT) of the right carotid artery and flow-mediated dilatation (FMD) of the right brachial artery.

RESULTS

Those with a VLBW had 1.1% units higher FMD (95% confidence interval [CI]: 0.0-2.2) (P = .06) and 0.5% units higher IMT relative to lumen size (95% CI: 0.1-0.9). IMT or FMD, when analyzed as the absolute change in millimeters, and carotid stiffness in the groups were similar. Among those with a VLBW, each 100-g-greater weight gain during the first 2 postnatal weeks predicted 1.1% units higher FMD (95% CI: 0.2-2.0) in adulthood.

CONCLUSIONS

Although young adults born at VLBWs, compared with those born at term, have higher levels of risk factors for cardiovascular disease, we found no clear evidence for elevated early markers of atherosclerosis. However, in relation to artery lumen diameter, IMT in the participants who had a VLBW was higher than in those who were born at term. In our study, weight gain during the first postnatal weeks had no harmful effect on the arteries in young adulthood.

Weight gain in infancy and early childhood is associated with school age body mass index but not intelligence and blood pressure in very low birth weight children

Rates of weight gain in infancy and early childhood can influence later neurocognitive, metabolic and cardiovascular health. We studied the relationship of weight gain during infancy and early childhood to intelligence quotient (IQ), blood pressure (BP) and body mass index (BMI) at age 9 in children born with very low birth weight (VLBW). Sixty-five children born prematurely with VLBW were followed longitudinally and at 9 years IQ, BP and BMI were measured. The mean weight z-scores at birth, neonatal intensive care discharge, 1 year corrected for prematurity, 5 and 9 years were -0.17, -2.09, -1.3, -0.68 and 0.06, respectively. Weight gain during infancy (discharge to 1 year corrected for prematurity) and early childhood (1 year corrected age to 5 years) was expressed as rate of change in weight, rate of change in weight z-score and interval change in weight z-score. In multiple regression analyses that adjusted for race, gender, maternal education, antenatal steroids, birth weight z-score, major intracranial lesions on ultrasound and chronic lung disease, rates of weight gain in infancy and early childhood were predictive of BMI z-score at 9 years, regression coefficients (95% confidence intervals); 0.19 (0.02, 0.36) and 0.37 (0.11, 0.63), respectively, expressed as change in BMI z-score per 10 g/week weight increase. Rates of weight gain were not predictive of systolic BP z-score, Verbal IQ or Performance IQ. In VLBW infants, more rapid weight gain during infancy, and especially early childhood, is associated with higher BMI at school age.

The effect of feto-maternal size and childhood growth on left ventricular mass and arterial stiffness in Afro-Caribbean children

We hypothesized that maternal size, fetal size and childhood growth are associated with childhood blood pressure, left ventricular mass (LVM) and arterial stiffness. The Vulnerable Windows Cohort is a longitudinal study of 569 mothers and their offspring. Anthropometry was measured on each child at birth, at 6 weeks, once in 3 months upto 2 years and then every 6 months. Blood pressure and body composition were assessed in 185 children (age 11.5 years) and echocardiography performed. LVM was not associated with maternal size after adjustment for child's weight. LVM was significantly associated with faster growth in childhood and with current weight, fat mass and lean mass. Systolic blood pressure was not related to maternal, fetal or newborn anthropometry, but was positively associated with infant and childhood growth, as well as current body size and fat mass. The pulse pressure/stroke volume ratio (an index of arterial stiffness) was inversely associated with maternal size, placental volume at 20 weeks, fetal size at 35 weeks and childhood growth even after adjustment for current weight. In conclusion, LVM in childhood is positively associated with maternal height, child's current size and rate of growth. Arterial stiffness is inversely related to maternal, fetal and placental size as well as growth throughout childhood.

Preterm birth--an emerging risk factor for adult hypertension?

Hypertension is a major risk factor for ischemic heart disease and stroke, which are leading causes of morbidity and death worldwide. Besides the contributions from genes and adult life-style, this review highlights that adult hypertension is likely to be a legacy of preterm birth. This knowledge has important health implications for the new and rapidly growing population of young people born very preterm. Increased awareness among both families and professionals about preterm birth being a perinatal risk factor for adult hypertension is needed. Measurement of blood pressure in children and young people born preterm is also recommended, all to detect and treat hypertension in young people born preterm long before end organ damage occurs.

Very preterm birth is a risk factor for increased systolic blood pressure at a young adult age

Children born very prematurely who show intrauterine growth retardation (IUGR) are suggested to be at risk of developing high blood pressure as adults. Renal function may already be impaired by young adult age. To study whether very preterm birth affects blood pressure in young adults, we measured 24-h ambulatory blood pressure (Spacelabs 90207 device) and renin concentration in 50 very premature individuals (<32 weeks of gestation), either small (SGA) or appropriate (AGA) for gestational age (21 SGA, 29 AGA), and 30 full-term controls who all were aged 20 years at time of measurement. The mean (standard deviation) daytime systolic blood pressure in SGA and AGA prematurely born individuals, respectively, was 122.7 (8.7) and 123.1 (8.5) mmHg. These values were, respectively, 3.6 mmHg [95% confidence interval (CI) -0.9 to 8.0] and 4.2 mmHg (95% CI 0.4-8.0) higher than in controls [119.6 (7.6)]. Daytime diastolic blood pressure and nighttime blood pressure did not differ between groups. We conclude that individuals born very preterm have higher daytime systolic blood pressure and higher risk of hypertension at a young adult age.

Parental and perinatal factors affecting childhood anthropometry of very-low-birth-weight premature infants: a population-based survey

BACKGROUND

The perinatal-neonatal course of very-low-birth-weight (VLBW) infants might affect their childhood growth. We evaluated the effect of parental anthropometry and perinatal and neonatal morbidity of VLBW neonates on their childhood growth.

METHODS

We obtained parental anthropometry, height and weight at age 6-10.5 years of 334 children born as VLBW infants. Parental, perinatal and neonatal data of these children were tested for association with childhood anthropometry.

RESULTS

(1) Maternal and paternal weight standard deviation score (SDS) and discharge weight (DW) SDS were associated with childhood weight SDS (R(2)= 0.111, p < 0.00001); (2) Maternal and paternal height SDS, corrected gestational age (GA) at discharge, maternal assisted reproduction and SGA status were associated with childhood height SDS (R(2)= 0.208, p < 0.00001); (3) paternal weight SDS, DW SDS and surfactant therapy were associated with childhood body mass index (BMI) SDS (R(2)= 0.096, p < 0.00001). 31.1% of VLBW infants had DW SDS < -1.88, and are to be considered small for gestational age ('SGA'). One quarter of these infants did not catch up by age 6-10.5 years.

CONCLUSION

Childhood anthropometry of VLBW infants depends on parental anthropometry, postnatal respiratory morbidity and growth parameters at birth and at discharge. Almost one-third of VLBW premature infants had growth restriction at discharge from neonatal intensive care unit (NICU), a quarter of whom did not catch up by age 6-10.5 years.

Blood pressure and heart rate patterns during sleep are altered in preterm-born infants: implications for sudden infant death syndrome

OBJECTIVE

Preterm infants are at an increased risk of sudden infant death syndrome, which may result from immature autonomic control of heart rate and blood pressure. Previous studies have demonstrated that preterm infants have altered heart rate and blood pressure control at term-equivalent age; however, little information is available beyond this age. The aim of this study was to determine the effect of preterm birth on heart rate and blood pressure control over the first 6 months of life after reaching term-equivalent age, including the age at which sudden infant death syndrome risk is increased, to understand the pathogenesis of sudden infant death syndrome.

METHODS

Preterm (n=25) and term (n=20) infants were studied longitudinally at 2 to 4 weeks', 2 to 3 months', and 5 to 6 months' term-corrected age by using daytime polysomnography. A photoplethysmographic cuff (Finometer) around the infant's wrist measured blood pressure during quiet and active sleep.

RESULTS

Blood pressure was lower in the preterm group during both quiet and active sleep at all ages studied. In contrast, there were no differences between groups in heart rate. Within the infants in the preterm group, blood pressure averaged lower at 2 to 3 months' corrected age compared with both 2 to 4 weeks' and 5 to 6 months' corrected age and was lower in quiet sleep compared with active sleep at all ages studied. Heart rate decreased with increasing age and was lower in quiet sleep compared with active sleep at 5 to 6 months' corrected age.

CONCLUSIONS

Sleep state and age affect heart rate and blood pressure patterns in prematurely born infants over the first 6 months of term-corrected age. It is notable that preterm infants had persistently lower blood pressure compared with age-matched term infants, signifying long-term alterations in cardiovascular control in infants born prematurely.

Low birth weight and the developing vascular tree: a systematic review

Low birth weight (LBW) is a risk factor for hypertension, stroke and coronary heart disease in adults. Mechanisms underlying cardiovascular disease may therefore be initiated in early life. Studies to investigate the initiating events and emergence of vascular risk markers in infancy and childhood have been an area of particular interest in recent years. The aim of this review is to focus on the early development of the human vascular tree in relation to LBW. Specific characteristics, including endothelial function, intima-media thickness, microvascular density, arterial dimensions and elasticity, will be discussed. LBW due to different causes--poor foetal growth or preterm birth--results in different patterns of altered development of the vascular system, which can already be seen in infancy. Follow-up studies in children and young adults indicate that vascular compromise in many ways persists in those born either small for gestational age or prematurely.

CONCLUSION

LBW is associated with structural and functional changes in the vascular tree, which have implications for cardiovascular health in adult life.