Risk of high blood pressure among young men increases with the degree of immaturity at birth

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

OBJECTIVES

We have previously reported an increased cardiac workload in newborn preterm small (SGA) infants, but not in infants appropriate for gestational age (AGA). We hypothesized that these cardiovascular changes will persist at follow-up at 5 years of age.

STUDY DESIGN

We assessed blood pressure, echocardiography, and skin perfusion with laser Doppler flowmetry in 22 SGA (821 +/- 248 g, 28.5 +/- 2.5 gestational weeks) and in 25 AGA (1065 +/- 241 g, 27.6 +/- 0.8 weeks) preterm children at age 5 years. Laser Doppler flowmetry also was used in 13 control children (3982 +/- 425 g, 40.4 +/- 1.8 weeks).

RESULTS

The preterm children in both the SGA and AGA groups had similar higher systolic blood pressures, increased interventricular septum thicknesses, and smaller left ventricular end-diastolic diameters compared with population reference values. Maximal endothelium-independent perfusion to sodium nitroprusside was higher and maximal endothelium-dependent perfusion to acetylcholine reached a plateau earlier in the AGA preterm group than in the control group.

CONCLUSIONS

Prematurity may impair cardiovascular function independently of intrauterine growth restriction. Altered cardiac dimensions and differences in perfusion responses may reflect increased cardiac afterload.

Successful breastfeeding after discharge of preterm and sick newborn infants

AIM

To determine the extent and duration of breastfeeding in preterm and sick newborn infants admitted to a level IIb neonatal unit (NU).

METHOD

Hospital-based follow-up of 1730 infants born in 1996, 2001 and 2004, and studied from discharge to 6 months of post-natal age.

RESULTS

At discharge from the NU, 98% of term (n = 945) and 92% of preterm (n = 785) infants were exclusively or partly breastfed. Exclusive breastfeeding increased at 2 months of corrected post-natal age and 78% of term infants were still exclusively or partly breastfed at 6 months of corrected post-natal age. Duration of breastfeeding among preterm infants was significantly shorter than in infants born at term. However, even among extremely preterm infants with a gestational age <28 weeks, 41% were still breastfeeding, exclusively or in part, at 6 months of post-natal age. There was no difference in breastfeeding after neonatal care in 1996 as compared to 2004. Moreover, the study showed that the breastfeeding after neonatal care differed only slightly from population data for all infants in Sweden.

CONCLUSION

Breastfeeding can be successfully established in most preterm and previously sick neonates.

Effects of early postnatal hypernutrition on nephron number and long-term renal function and structure in rats

Various antenatal events impair nephrogenesis in humans as well as in several animal models. The consecutive low nephron endowment may contribute to an increased risk for cardiovascular and renal diseases in adulthood. However, little knowledge is available on the influence of the postnatal environment, especially nutrition, on nephrogenesis. Moreover, the consequences of early postnatal nutrition in late adulthood are not clear. We used a model of early postnatal overfeeding (OF) induced by reduction of litter size (3 pups/litter) in rats. Systolic blood pressure (SBP; plethysmography), glomerular filtration rate (clearance of creatinine), glomerular number and volume, and glomerulosclerosis were evaluated in 22-mo-old aging offspring. Early postnatal OF was associated with increased weight gain during the suckling period (+40%, P < 0.01) and a 20% increase in glomerular number (P < 0.05). However, an increase in SBP at 12 mo by an average of 18 mmHg and an increase in proteinuria (2.6-fold) and glomerulosclerosis at 22 mo of age were observed in OF male offspring compared with controls. In conclusion, early postnatal OF in the rat enhances postnatal nephrogenesis, but elevated blood pressure and glomerulosclerosis are still observed in male adults. Factors other than glomerular number reduction are likely to contribute to the arterial hypertension induced by early postnatal OF.

Renal glomeruli and tubular injury following indomethacin, ibuprofen, and gentamicin exposure in a neonatal rat model

Indomethacin, ibuprofen, and gentamicin are commonly administered to neonates between 24 and 28 wk gestation when glomerulogenesis is still occurring. Indomethacin is known to cause renal failure in up to 25% of infants treated. Possible morphologic effects of these drugs are largely unknown. The purpose of this study was to determine the type of renal changes found on light (LM) and electron microscopy (EM) following administration of indomethacin, ibuprofen, and gentamicin in a neonatal rat model. Rat pups were exposed to indomethacin or ibuprofen and/or gentamicin antenatally for 5 d before birth or postnatally for 5 d from d 1 of life. Pups were killed at 14 d of age. LM examination in all indomethacin- and ibuprofen-treated pups both antenatally and postnatally showed vacuolization of the epithelial proximal tubules, interstitial edema, intratubular protein deposition but no significant glomerular changes. EM examination showed pleomorphic mitochondria and loss of microvilli in the tubules. The glomeruli showed extensive foot process effacement and irregularities of the glomerular basement membrane. EM changes were most marked in pups treated antenatally with ibuprofen, and indomethacin with gentamicin postnatally. Indomethacin, ibuprofen, and gentamicin cause significant change in glomerular and tubular structure in the neonatal rat model.

Impact de l'âge gestationnel et du poids de naissance sur le devenir cardiovasculaire à long terme

PURPOSE

Intra-uterine growth restriction and preterm birth can lead to cardiovascular diseases in adulthood.

CURRENT KNOWLEDGE AND KEY POINTS

Preterm birth and intra-uterine growth restriction induce long-term changes in organ development such as arterial system and kidney function. Among these changes, the impairment of arterial wall structure or properties occurring in low birth weight babies, as a result of preterm birth and intra-uterine growth restriction, may lead on a long-term to an elevation of arterial pressure and arterial stiffness. These notions are still not completely understood and seem of high importance in regard to the high frequency in preterm birth and intra-uterine growth restriction.

FUTURE PROSPECTS AND PROJECTS

Identifying clinical, paraclinical markers and better understanding a link between adverse perinatal conditions and cardiovascular diseases might improve actions for preventing cardiovascular diseases in adulthood in this population.

Increased catecholamines and heart rate in children with low birth weight: perinatal contributions to sympathoadrenal overactivity

BACKGROUND

Low birth weight is associated with cardiovascular disease. The underlying mechanisms are unknown. We hypothesized that perinatal stress alters autonomic regulation of the cardiovascular system. In this study, catecholamines, heart rate (HR) and blood pressure (BP) were measured in healthy children with low birth weight.

METHODS

This clinical study included 105 children (mean age 9.6 years) in three groups; born at term with normal birth weight (controls, n=37), born at term but small for gestational age (SGA, n=29) and born preterm (Preterm, n=39). Dopamine, adrenaline and noradrenaline were determined in urine. HR and BP were measured at rest, during an orthostatic test and after a mathematical mental stress test.

RESULTS

Children in the Preterm and SGA groups excreted higher levels of catecholamines when compared with controls. HR (mean [SD] values) were higher at rest and after mental stress in Preterm (at rest 76 [9] and after mental stress 82 [12] min(-1)) and in SGA (79 [8] and 82 [10]) when compared with controls (70 [9] and 75 [9]). HR correlated with urinary catecholamines (r=0.24-0.27, P<0.05). Blood pressures measured at rest, during orthostatic testing and after mental stress did not differ between the groups.

CONCLUSIONS

Preterm birth and fetal growth restriction are associated with increased sympathoadrenal activity in childhood, as indicated by stress-induced increases in HR and urinary catecholamines. These findings suggest that the cardiovascular control is differently programmed in these children with possibly higher risk of developing hypertension in adulthood.

The Uppsala studies on developmental origins of health and disease

Large-scale epidemiological studies on developmental origins of health running in Uppsala benefit from the accessibility of well-archived and high quality Swedish records, high participation rates in the surveys, and a long tradition of interdisciplinary research and international collaboration. The UBCoS Multigen study is unique in being able to study intergenerational determinants of health and health inequalities as 'forward in time' processes, starting at the beginning of the last century, whilst the Uppsala Family and ULSAM studies contribute evidence on gene-environment interactions and specific mechanisms of developmental origins of circulatory diseases.

Cardiovascular risk factors at age 30 following pre-term birth

BACKGROUND

Recent epidemiological evidence has shown increased rates of cardiovascular mortality and associated risk factors in those born small. However, scarce information exists concerning cardiovascular risk factors in adulthood following pre-term birth, or distinguishing the relative contributions of length of gestation and fetal growth to small size at birth.

METHODS

Prospective follow-up of 458 30-year-olds whose mothers took part in a randomized controlled trial of antenatal betamethasone for the prevention of neonatal respiratory distress syndrome (147 born at term, 311 born pre-term). Follow-up assessments included anthropometry, blood pressure, blood lipids, early morning cortisol levels and 75 g oral glucose tolerance test.

RESULTS

Gestational age at birth, pre-term birth, and birth weight z-score were not associated with serum cholesterol, triglyceride or cortisol at age 30 (P > 0.1 for all). However, pre-term birth was associated with increased systolic blood pressure (3.5 mmHg, 95% CI 0.9-6.1 mmHg, P = 0.009) and insulin resistance at age 30 [Log (Insulin area under the curve) = 0.17, 95% CI 0.05-0.28, P = 0.006]. Low gestational age at birth was also associated with these outcomes, whereas birth weight, adjusted for gestational age, was not.

CONCLUSIONS

Adults who were born moderately pre-term have increased blood pressure and insulin resistance at 30 years of age. Pre-term birth rather than poor fetal growth is the major determinant of this association. As both the incidence of pre-term birth and survival amongst those born pre-term are increasing, this group may contribute an increasing proportion to overall cardiovascular disease burden.

Cardiovascular reactivity to psychological stressors in late adulthood is predicted by gestational age at birth

The relationships of body size and gestational age at birth with adult blood pressure (BP) are relatively modest compared to their stronger associations with cardiovascular disease. BP reactivity is a strong predictor of cardiovascular morbidity, and it is possible that reactivity, rather than resting level, is determined in utero. We investigated whether body size and gestational age at birth predict BP reactivity during experimentally induced psychosocial stress in late adulthood. A total of 73 men and 80 women born after 36 weeks' gestation in Helsinki, Finland, during 1934-1944 underwent the Trier Social Stress Test (TSST); a standardized psychosocial stress test consisting of a public speech and an arithmetic task. Changes in BP were monitored continuously by a non-invasive finger photoplethysmography (Finometer, FMS, Amsterdam, The Netherlands). The results showed that the most robust early determinant of BP reactivity was gestational age; however, with opposite relationships between the sexes (P for interaction <0.001). A 1-week increase in gestational age was associated with a 3.1 mm Hg (95% confidence interval (CI), 0.2 to 6.0) and 1.2 mm Hg (95% CI, -0.1 to 2.6) decreases in systolic and diastolic BP reactivity in women, but with 5.2 mm Hg (95% CI, 1.9 to 8.4) and 2.3 mm Hg (95% CI, 0.9 to 3.8) increases in men. In conclusion, normal variation in gestational age at birth predicts cardiovascular stress reactivity in later adulthood. Given that hypothalamic-pituitary-adrenal axis contributes to the regulation of autonomic nervous system function and the timing of parturition, and shows well-established sex differences, we speculate a role for early programming of this axis in explaining the findings.

Abnormal circulatory stress responses of preterm graduates

Preterm birth and chronic lung disease may increase the risk of hypertension and cardiovascular disease in infancy and adolescence. Here we looked for evidence of early circulatory dysfunction associated with these perinatal complications. We compared infants born at term (n = 12) with those born preterm with an uncomplicated neonatal course (n = 12) or diagnosed with bronchopulmonary dysplasia (BPD) (n = 10). We measured blood pressure (BP) (Finometer), and heart rate (HR) responses to 4 min of breathing 4% CO2 during quiet sleep. Hypercapnia accelerated HR and increased BP of term infants. Preterm infants either (i) had an exaggerated pressor but little or no HR response to CO2 (healthy or mild-moderate BPD) or (ii) had a diminished pressor response and accompanying decrease in HR (severe BPD). Short-term reflex cardiovascular control was consequently altered by premature birth, with potentially more serious aberrations associated with severe BPD. Most anomalies had not resolved by the time infants born preterm reached term age; some may be early signs of emerging long-term cardiovascular dysfunction.

Using the LMS method to calculate z-scores for the Fenton preterm infant growth chart

OBJECTIVES

The use of exact percentiles and z-scores permit optimal assessment of infants' growth. In addition, z-scores allow the precise description of size outside of the 3rd and 97th percentiles of a growth reference. To calculate percentiles and z-scores, health professionals require the LMS parameters (Lambda for the skew, Mu for the median, and Sigma for the generalized coefficient of variation; Cole, 1990). The objective of this study was to calculate the LMS parameters for the Fenton preterm growth chart (2003).

DESIGN

Secondary data analysis of the Fenton preterm growth chart data.

METHODS

The Cole methods were used to produce the LMS parameters and to smooth the L parameter. New percentiles were generated from the smooth LMS parameters, which were then compared with the original growth chart percentiles.

RESULTS

The maximum differences between the original percentile curves and the percentile curves generated from the LMS parameters were: for weight; a difference of 66 g (2.9%) at 32 weeks along the 90th percentile; for head circumference; some differences of 0.3 cm (0.6-1.0%); and for length; a difference of 0.5 cm (1.6%) at 22 weeks on the 97th percentile.

CONCLUSION

The percentile curves generated from the smoothed LMS parameters for the Fenton growth chart are similar to the original curves. These LMS parameters for the Fenton preterm growth chart facilitate the calculation of z-scores, which will permit the more precise assessment of growth of infants who are born preterm.

Associations of gestational age and intrauterine growth with systolic blood pressure in a family-based study of 386,485 men in 331,089 families

BACKGROUND

We conducted a family-based study to explore mechanisms underlying the associations of birth weight and gestational age with systolic blood pressure measured at 17 to 19 years of age.

METHODS AND RESULTS

A record linkage study of 386,485 singleton-born men from 331,089 families was undertaken. Birth weight was inversely associated with systolic blood pressure within siblings, with a mean difference (adjusted for age at examination, examination center, and year of examination) within siblings per 1-SD difference in birth weight of -0.21 mm Hg (95% CI, -0.33 to -0.08) and between nonsiblings of -0.12 (95% CI, -0.16 to -0.08). Gestational age was inversely associated with systolic blood pressure within siblings (-0.18 mm Hg; 95% CI, -0.25 to -0.11, per week of gestational age) and between nonsiblings (-0.26 mm Hg; 95% CI, -0.29 to -0.24). Adjustment for socioeconomic position and maternal characteristics did not alter these within- or between-family associations. Furthermore, the associations were not affected by adjustment for paternal height, body mass index, or systolic blood pressure.

CONCLUSIONS

Our present findings suggest that the inverse associations of birth weight and gestational age with systolic blood pressure are not explained by confounding resulting from family socioeconomic position or other factors that are shared by siblings. Variations in maternal metabolic or vascular health during pregnancy or placental implantation and function may explain these associations.

Preterm birth in Sweden: what are the average lengths of hospital stay and the associated inpatient costs?

AIM

To provide estimates of the first-year length of stay and inpatient costs of Swedish infants admitted for neonatal care by week of gestation and by birthweight; and to provide estimates of the length of stay and inpatient costs of delivering mothers during the ante- and postpartum period by week of gestation and birthweight of the infant.

METHODS

Population-based registry study covering all live singleton deliveries in Sweden between 1998 and 2001 (n=336 136). First-year hospitalizations of infants admitted for neonatal care 0-6 d after birth (n=24 583) were tracked, as were hospitalizations of mothers for whom the date of admission lay+/-1 mo from the date of delivery. Monetary values were assigned to each hospitalization using the Nord-DRG classification system.

RESULTS

On average, preterm infants (GA < 37 wk) had first-year lengths of stay roughly four times as long as full-term infants admitted for neonatal care (30 d vs 8 d, p<0.0001). The average first-year length of stay of the extremely immature infants (GA 22-25 wk) was more than six times as long that of infants born at 34-36 wk (108 d vs 17 d, p<0.0001). Mothers delivering preterm had an average length of stay slightly more than twice as long (p<0.0001) as that of mothers of full-term infants during the ante- and postpartum period.

CONCLUSION

The estimated lengths of stay and costs may serve as reference values for a Swedish setting.

Characteristics of arterial stiffness in very low birth weight premature infants

Premature birth is a factor of increased blood pressure in adulthood. Little is known about the physiologic characteristics of the arterial bed in neonates. The aim of this study was to characterize in vivo the arterial compliance in neonates and its maturation profile in very low birth weight (VLBW) premature infants. A group of stable, VLBW premature infants was compared with a control group of near term neonates. The abdominal aortic wall distensibility coefficient (DC) and whole-body arterial compliance (WBAC) were determined using specifically designed noninvasive methods, based on ultrasonic measurements in combination with synchronous, beat-to-beat recording of aortic pulse pressure (PP). On the fifth day of life, WBAC and the CD were lower in VLBW premature infants than in controls. Furthermore, WBAC and the DC remained unchanged in VLBW premature infants 7 wk after birth. In conclusion, VLBW premature infants are characterized as early as the fifth day of life by high arterial stiffness, which persists when they reach their theoretical term. It can be speculated that early alteration of arterial elastic properties may pave the way for long-term elevation of arterial pressure in VLBW premature infants.

Early renal structure alteration in rat offspring from dams fed low protein diet

To investigate the early renal alterations due to severe maternal protein restriction (MPR) Wistar dams received 23% (normal protein, NP) or 5% (low protein, LP) chow during gestation and lactation periods. In NP offspring at birth, the cortex-to-medulla (C/M) ratio was 35% greater in female than in male offspring and the mature/immature glomeruli ratio was lower in both sexes of LP offspring than in the matched NP ones (by 20%). At birth and at weaning the kidney of the LP offspring showed fewer glomeruli (40% less) than the age-matched NP offspring. The NP female offspring had almost 20% fewer glomeruli than the matched male offspring. At weaning, the number of glomeruli was positively correlated with BM at birth (R=0.86; P<0.001). The effects of gender and maternal protein restriction, both individually and overall, based on biometrical and stereological parameters were: day 1, MPR largely responsible for the majority of alterations observed in LP groups, however gender influenced C/M ratio; day 21, MPR and gender interacted and modified the number of glomeruli per kidney. The early adverse of MPR effect on renal development is disproportionate between mature and immature glomeruli at birth leading to fewer glomeruli at weaning. This supports epidemiological data in humans underlying why fetuses with low birth weight carry an increased risk of mortality from chronic diseases in adulthood, including hypertension.