The evolution of neonatology

Resting energy expenditure in young adults born preterm--the Helsinki study of very low birth weight adults

Background

Adults born preterm with very low birth weight (VLBW; <1500g) have higher levels of cardiovascular and metabolic risk factors than their counterparts born at term. Resting energy expenditure (REE) could be one factor contributing to, or protecting from, these risks. We studied the effects of premature birth with VLBW on REE.

Methodology/Principal Findings

We used indirect calorimetry to measure REE and dual x-ray absorptiometry (DXA) to measure lean body mass (LBM) in 116 VLBW and in 118 term-born control individuals (mean age: 22.5 years, SD 2.2) participating in a cohort study. Compared with controls VLBW adults had 6.3% lower REE (95% CI 3.2, 9.3) adjusted for age and sex, but 6.1% higher REE/LBM ratio (95% CI 3.4, 8.6). These differences remained similar when further adjusted for parental education, daily smoking, body fat percentage and self-reported leisure time exercise intensity, duration and frequency.

Conclusions/Significance

Adults born prematurely with very low birth weight have higher resting energy expenditure per unit lean body mass than their peers born at term. This is not explained by differences in childhood socio-economic status, current fat percentage, smoking or leisure time physical activity. Presence of metabolically more active tissue could protect people with very low birth weight from obesity and subsequent risk of chronic disease.

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.

Mothers' and fathers' birth characteristics and perinatal mortality in their offspring: a population-based cohort study

There is increasing interest in the associations between parental birthweight and gestational age with their perinatal outcomes. We investigated perinatal mortality risk in offspring in relation to maternal and paternal gestational age and birthweight. We used population-based generational data from the Medical Birth Registry of Norway, 1967-2006. Singletons in both generations were included, forming 520,794 mother-offspring and 376,924 father-offspring units. Perinatal mortality in offspring was not significantly associated with paternal gestational age or birthweight, whereas it was inversely associated with maternal gestational age. A threefold increased risk in perinatal mortality was found among offspring of mothers born at 28-30 weeks of gestation relative to offspring of mothers born at term (37-43 weeks) (relative risk: 2.9, 95% CI 1.9, 4.6). There was also an overall association between maternal birthweight and offspring perinatal mortality. Relative risk for mothers whose birthweight was <2000 g was 1.5 (95% CI 1.1, 1.9), relative to mothers whose birthweight was 3500-3999 g. However, confined to mothers born at >or=34 weeks of gestation, the birthweight association was not significant. Weight-specific perinatal mortality in offspring was dependent on the birthweight of the mother and the father, that is, offspring who were small relative to their mother's or father's birthweight had increased perinatal mortality. In conclusion, a mother's gestational age, and not her birthweight, was significantly associated with perinatal mortality in the offspring, while there was no such association for the father.

Ambulatory blood pressure in young adults with very low birth weight

OBJECTIVE

We hypothesized that, as compared with a matched control group born at term, young adults with very low birth weight (VLBW <1.5 kg) would have higher 24-hour ambulatory blood pressure.

STUDY DESIGN

We studied 118 18- to 27-year-old subjects born with VLBW within the greater Helsinki area and 120 term-born control subjects with similar age, sex, and birth hospital. The mean birth weight for VLBW subjects was 1.1 kg (standard deviation [SD], 0.2) and for controls, 3.6 kg (SD, 0.5). Gestational ages were 29.2 (SD, 2.3) and 40.1 (SD, 1.0) weeks. Current education of higher-educated parents served as an indicator of childhood socioeconomic status. Ambulatory blood pressure was measured during a 24-hour period with an oscillometric device (Spacelabs 90207).

RESULTS

VLBW subjects had, with sex, age, and body mass index adjustment, a 2.4 mm Hg (95% confidence interval, 0.2 to 4.6) higher 24-hour systolic pressure. We found hypertension in 11 VLBW subjects and in 3 term-born subjects, giving an adjusted odds ratio of 4.0 (1.1 to 14.8). When socioeconomic status was taken into account, results remained unchanged.

CONCLUSIONS

Higher rates of hypertension and higher 24-hour blood pressure among young adults with VLBW may indicate higher risk for adverse cardiovascular outcomes.

Influence of the calcium concentration in the presence of organic phosphorus on the physicochemical compatibility and stability of all-in-one admixtures for neonatal use

BACKGROUND

Preterm infants need high amounts of calcium and phosphorus for bone mineralization, which is difficult to obtain with parenteral feeding due to the low solubility of these salts. The objective of this study was to evaluate the physicochemical compatibility of high concentrations of calcium associated with organic phosphate and its influence on the stability of AIO admixtures for neonatal use.

METHODS

Three TPN admixture formulas were prepared in multilayered bags. The calcium content of the admixtures was adjusted to 0, 46.5 or 93 mg/100 ml in the presence of a fixed organic phosphate concentration as well as lipids, amino acids, inorganic salts, glucose, vitamins and oligoelements at pH 5.5. Each admixture was stored at 4 degrees C, 25 degrees C or 37 degrees C and evaluated over a period of 7 days. The physicochemical stability parameters evaluated were visual aspect, pH, sterility, osmolality, peroxide formation, precipitation, and the size of lipid globules.

RESULTS

Color alterations occurred from the first day on, and reversible lipid film formation from the third day of study for the admixtures stored at 25 degrees C and 37 degrees C. According to the parameters evaluated, the admixtures were stable at 4 degrees C; and none of them presented precipitated particles due to calcium/phosphate incompatibility or lipid globules larger than 5 mum, which is the main parameter currently used to evaluate lipid emulsion stability. The admixtures maintained low peroxide levels and osmolarity was appropriate for parenteral administration.

CONCLUSION

The total calcium and calcium/phosphorus ratios studied appeared not to influence the physicochemical compatibility and stability of AIO admixtures.

Long-term survival and reproduction in preterm infants

The rate of preterm birth is increasing in developed countries. Improvements in neonatal intensive care have decreased the rate of infant mortality after preterm birth, particularly for those born at the earliest gestational ages. However, the result is an increasing absolute number of preterm birth survivors who suffer from disabilities such as neurosensory, respiratory and cognitive impairments. Evidence is also accumulating demonstrating that these survivors may be at increased risk for mortality, even into later childhood, and that they may face challenges transitioning into adulthood, such as a decreased likelihood of reproduction.

Kernicterus in the 21st century: frequently asked questions

Acute kernicterus remains a clinical emergency and its delayed management represents an easily preventable neonatal brain injury. Yet, practitioners encounter recurrent questions regarding the risk and timing of bilirubin-related neurotoxicity. These include the following: does bilirubin damage the brain of healthy infants? Is there a re-emergence of kernicterus in the United States? Was kernicterus previously prevented in the United States? What was the public health impact of 1994 American Academy of Pediatrics Guidelines? What is the current incidence of kernicterus and severe neonatal hyperbilirubinemia? What is the estimated risk of kernicterus in infants with excessive hyperbilirubinemia? Is there a specific bilirubin threshold total serum bilirubin (TSB) value for neurotoxicity? Are there sequelae of severe or prolonged moderate hyperbilirubinemia in the absence of recognized acute bilirubin encephalopathy? Can we define a bilirubin level that is safe in newborns? We address these questions in the context of available data and evidence, and estimate the current risk of chronic kernicterus is about one in seven in infants with TSB >30 mg per 100 ml (513 micromol l(-1)).

Thyroid system immaturities in very low birth weight premature infants

Continuing advances in the care of premature infants has contributed to the increased survival of very low birth weight premature infants. These infants are characterized by a variety of organ and physiological systems immaturities predisposing to deficiencies of postnatal adaptation and a high prevalence of neonatal morbidities. These morbidities have a major impact on postnatal mental and neurological outcomes. Thyroid hormones play a critical role in central nervous system development and function, and thyroid system immaturities as well as morbidity-related thyroid dysfunction (the nonthyroidal illness syndrome) contribute to the transient hypothyroxinemia of premature infants (THOP). Several studies have demonstrated a correlation of THOP with subsequent low IQ and neurologic sequelae in very low birth weight premature infants, and there is suggestive evidence that thyroid hormone supplementation in very low birth weight infants can improve mental outcome. Here, we review normal fetal thyroid system development and the system immaturities contributing to THOP and predisposing to nonthyroidal illness in very low birth weight infants.

Biomarkers in neonatal infection

Infected newborn infants are often difficult to differentiate from patients suffering from noninfective diseases. Whilst delaying treatment with antibiotics of infected infants may be fatal, widespread indiscriminate use in all cases with suspected bacterial infection could lead to both drug-induced complications and the development of multidrug-resistant organisms. Conventional biomarkers, such as blood cell counts and morphology, have serious limitations. Investigators in this area of research have, therefore, made strenuous efforts to discover more reliable biomarkers with superior diagnostic utilities and clinically relevant characteristics to help neonatal clinicians differentiate between infected and noninfected infants. The major classes of biomarkers in neonatal infection of recent interest will be discussed, including: acute phase reactants, cytokines, chemokines and leukocyte surface antigens. The application of these biomarkers to derive prognostic information useful to neonatal clinicians will also be considered.

Glucose regulation in young adults with very low birth weight

BACKGROUND

The association between small size at birth and impaired glucose regulation later in life is well established in persons born at term. Preterm birth with very low birth weight (<1500 g) is also associated with insulin resistance in childhood. If insulin resistance persists into adulthood, preterm birth with very low birth weight also may be associated with an increased risk of disease in adulthood. We assessed glucose tolerance and insulin sensitivity and measured serum lipid levels and blood pressure in young adults with very low birth weight.

METHODS

We performed a standard 75-g oral glucose-tolerance test, measuring insulin and glucose concentrations at baseline and at 120 minutes in 163 young adults (age range, 18 to 27 years) with very low birth weight and in 169 subjects who had been born at term and were not small for gestational age. The two groups were similar with regard to age, sex, and birth hospital. We measured blood pressure and serum lipid levels, and in 150 very-low-birth-weight subjects and 136 subjects born at term, we also measured body composition by means of dual-energy x-ray absorptiometry.

RESULTS

As compared with the subjects born at term, the very-low-birth-weight subjects had a 6.7% increase in the 2-hour glucose concentration (95% confidence interval [CI], 0.8 to 12.9), a 16.7% increase in the fasting insulin concentration (95% CI, 4.6 to 30.2), a 40.0% increase in the 2-hour insulin concentration (95% CI, 17.5 to 66.8), an 18.9% increase in the insulin-resistance index determined by homeostatic model assessment (95% CI, 5.7 to 33.7), and an increase of 4.8 mm Hg in systolic blood pressure (95% CI, 2.1 to 7.4). Adjustment for the lower lean body mass in the very-low-birth-weight subjects did not attenuate these relationships.

CONCLUSIONS

Young adults with a very low birth weight have higher indexes of insulin resistance and glucose intolerance and higher blood pressure than those born at term.

Gastrointestinal development and meeting the nutritional needs of premature infants

The fear of necrotizing enterocolitis and feeding intolerance are major factors inhibiting the use of the enteral route as the primary means of nourishing premature infants. Parenteral nutrition may help to meet many of the nutritional needs of these infants, but has significant detrimental side effects that include intestinal atrophy, sepsis, and increased susceptibility to inflammatory stimuli and systemic inflammatory responses. Being able to minimize the use of the parenteral route and still maintain appropriate nutrition safely would be a major advance in neonatology. At the basis of our inability to use the enteral route is a poorly understood immature gastrointestinal tract. Approaches such as minimal enteral nutrition or trophic feedings may partially alleviate these problems. However, if we are to progress in greater utilization of the gastrointestinal tract, other factors need to be considered. These include the macronutrient composition of minimal enteral or trophic feedings and the microecology of the intestinal lumen. Some of the developmental aspects of the intestine, which include intestinal growth, motor activity, barrier and other innate immune functions, and the microecology of the developing intestine, are briefly reviewed here. The purpose of this review is to suggest important areas of future research in neonatal and developmental gastroenterology that could affect several conditions that are related to immaturity of the gastrointestinal tract.