Long-term adverse outcomes of low birth weight, increased somatic growth rates, and alterations of body composition in the premature infant: review of the evidence

Early Neonatal Pain-A Review of Clinical and Experimental Implications on Painful Conditions Later in Life

Modern health care has brought our society innumerable benefits but has also introduced the experience of pain very early in life. For example, it is now routine care for newborns to receive various injections or have blood drawn within 24 h of life. For infants who are sick or premature, the pain experiences inherent in the required medical care are frequent and often severe, with neonates requiring intensive care admission encountering approximately fourteen painful procedures daily in the hospital. Given that much of the world has seen a steady increase in preterm births for the last several decades, an ever-growing number of babies experience multiple painful events before even leaving the hospital. These noxious events occur during a critical period of neurodevelopment when the nervous system is very vulnerable due to immaturity and neuroplasticity. Here, we provide a narrative review of the literature pertaining to the idea that early life pain has significant long-term effects on neurosensory, cognition, behavior, pain processing, and health outcomes that persist into childhood and even adulthood. We refer to clinical and pre-clinical studies investigating how early life pain impacts acute pain later in life, focusing on animal model correlates that have been used to better understand this relationship. Current knowledge around the proposed underlying mechanisms responsible for the long-lasting consequences of neonatal pain, its neurobiological and behavioral effects, and its influence on later pain states are discussed. We conclude by highlighting that another important consequence of early life pain may be the impact it has on later chronic pain states-an area of research that has received little attention.

Adult Consequences of Extremely Preterm Birth: Cardiovascular and Metabolic Diseases Risk Factors, Mechanisms, and Prevention Avenues

Extremely preterm babies are exposed to various sources of injury during critical stages of development. The extremely preterm infant faces premature transition to ex utero physiology and undergoes adaptive mechanisms that may be deleterious in the long term because of permanent alterations in organ structure and function. Perinatal events can also directly cause structural injury. These disturbances induce morphologic and functional changes in their organ systems that might heighten their risks for later adult chronic diseases. This review examines the pathophysiology of programming of long-term health and diseases after preterm birth and associated perinatal risk factors.

Lung Function and Bronchial Hyperresponsiveness in Adults Born Prematurely. A Cohort Study

RATIONALE

Bronchopulmonary dysplasia and the long-term consequences of prematurity are underrecognized entities, unfamiliar to adult clinicians. Well described by the pediatric community, these young adults are joining the ranks of a growing population of adults with chronic lung disease.

OBJECTIVES

To describe the quality of life, pulmonary lung function, bronchial hyperresponsiveness, body composition, and trends in physical activity of adults born prematurely, with or without respiratory complications.

METHODS

Four groups of young adults born in Canada between 1987 and 1993 were enrolled in a cohort study: (1) preterm subjects with no neonatal respiratory complications, (2) preterm subjects with neonatal respiratory distress syndrome, (3) preterm subjects with bronchopulmonary dysplasia, and (4) subjects born at term. The following measurements were compared across the four groups: health-related quality of life, respiratory health, pulmonary function, methacholine challenge test results, and sedentary behavior and physical activity level.

MEASUREMENTS AND MAIN RESULTS

Adult subjects who had bronchopulmonary dysplasia in infancy had mild airflow obstruction (FEV1, 80% predicted; FEV1/FCV ratio, 70) and gas trapping compared with others. They also had less total active energy expenditure and more time spent in sedentary behavior compared with subjects born at term. All preterm groups had a high prevalence of bronchial hyperresponsiveness compared with term subjects.

CONCLUSIONS

In a population-derived, cross-sectional study, we confirmed previous reports that adults 21 or 22 years of age who were born prematurely with neonatal bronchopulmonary dysplasia are more likely to have airflow obstruction, bronchial hyperresponsiveness, and pulmonary gas trapping than subjects born prematurely without bronchopulmonary dysplasia or at term. Clinicians who care for adults need to be better informed of the long-term respiratory consequences of premature birth to assist young patients in maintaining lung function and health.

Modification of nutrition strategy for improvement of postnatal growth in very low birth weight infants

Purpose

To identify the effects of modified parenteral nutrition (PN) and enteral nutrition (EN) regimens on the growth of very low birth weight (VLBW) infants.

Methods

The study included VLBW infants weighing <1,500 g, admitted to Chungnam National University Hospital between October 2010 and April 2014, who were alive at the time of discharge. Subjects were divided according to 3 periods: period 1 (n=37); prior to the PN and EN regimen being modified, period 2 (n=50); following the PN-only regimen modification, period 3 (n=37); following both PN and EN regimen modification. The modified PN regimen provided 3 g/kg/day of protein and 1 g/kg/day of lipid on the first day of life. The modified EN regimen provided 3.5-4.5 g/kg/day of protein and 150 kcal/kg/day of energy. We investigated growth rate, anthropometric measurements at 40 weeks postconceptional age (PCA) and the incidence of extrauterine growth restriction (EUGR) at 40 weeks PCA.

Results

Across the 3 periods, clinical characteristics, including gestational age, anthropometric measurements at birth, multiple births, sex, Apgar score, surfactant use and PDA treatment, were similar. Growth rates for weight and height, from time of full enteral feeding to 40 weeks PCA, were higher in period 3. Anthropometric measurements at 40 weeks PCA were greatest in period 3. Incidence of weight, height and head circumference EUGR at 40 weeks PCA decreased in period 3.

Conclusion

Beginning PN earlier, with a greater supply of protein and energy during PN and EN, is advantageous for postnatal growth in VLBW infants.

Postnatal growth failure in very low birthweight infants born between 2005 and 2012

BACKGROUND

Postnatal growth restriction is common in preterm infants and is associated with long-term neurodevelopmental impairment. Recent trends in postnatal growth restriction are unclear.

METHODS

Birth and discharge weights from 25,899 Californian very low birthweight infants (birth weight 500-1500 g, gestational age 22-32 weeks) who were born between 2005 and 2012 were converted to age-specific Z-scores and analysed using multivariable modelling.

RESULTS

Birthweight Z-score did not change between 2005 and 2012. However, the adjusted discharge weight Z-score increased significantly by 0.168 Z-scores (0.154, 0.182) over the study period, and the adjusted fall in weight Z-score between birth and discharge decreased significantly between those dates (by 0.016 Z-scores/year). The proportion of infants who were discharged home below the 10th weight-for-age centile or had a fall in weight Z-score between birth and discharge of >1 decreased significantly over time. The comorbidities most associated with poorer postnatal growth were medical or surgical necrotising enterocolitis, isolated gastrointestinal perforation and severe retinopathy of prematurity, which were associated with an adjusted mean reduction in discharge weight Z-score of 0.24, 0.57, 0.46 and 0.32, respectively. Chronic lung disease was not a risk factor after accounting for length of stay.

CONCLUSIONS

Postnatal, but not prenatal, growth improved among very low birthweight infants between 2005 and 2012. Neonatal morbidities including necrotising enterocolitis, gastrointestinal perforations and severe retinopathy of prematurity have significant negative effects on postnatal growth.

Effects of postnatal growth restriction and subsequent catch-up growth on neurodevelopment and glucose homeostasis in rats

Background

There is increasing evidence that poor growth of preterm infants is a risk factor for poor long-term development, while the effects of early postnatal growth restriction are not well known. We utilized a rat model to examine the consequences of different patterns of postnatal growth and hypothesized that early growth failure leads to impaired development and insulin resistance. Rat pups were separated at birth into normal (N, n = 10) or restricted intake (R, n = 16) litters. At d11, R pups were re-randomized into litters of 6 (R-6), 10 (R-10) or 16 (R-16) pups/dam. N pups remained in litters of 10 pups/dam (N-10). Memory and learning were examined through T-maze test. Insulin sensitivity was measured by i.p. insulin tolerance test and glucose tolerance test.

Results

By d10, N pups weighed 20 % more than R pups (p < 0.001). By d15, the R-6 group caught up to the N-10 group in weight, the R-10 group showed partial catch-up growth and the R-16 group showed no catch-up growth. All R groups showed poorer scores in developmental testing when compared with the N-10 group during T-Maze test (p < 0.05). Although R-16 were more insulin sensitive than R-6 and R-10, all R groups were more glucose tolerant than N-10.

Conclusion

In rats, differences in postnatal growth restriction leads to changes in development and in insulin sensitivity. These results may contribute to better elucidating the causes of poor developmental outcomes in human preterm infants.

Maternal attention and preterm infant feeding

PURPOSE

The purpose of this study was to explore the relationships among the mother's internal working model of feeding, attentional process, feeding behaviors, and responsiveness accounting for maternal psychological distress, which may contribute to preterm infants' feeding difficulties.

DESIGN AND METHODS

In this descriptive study, 21 mother-preterm infant dyads were videotaped during feeding.

RESULTS

Surprisingly, the internal working model of feeding was a significant negative predictor of maternal feeding behaviors and maternal attention. All other correlations were non-significant.

CONCLUSIONS

Given the early timing of the data collection, it is possible that mothers had not developed a frame of reference of their infant as a person. Research to help further understand factors and timing affecting maternal feeding behaviors is needed.

Assessment of Infant Movement With a Compact Wireless Accelerometer System

There is emerging data that patterns of motor activity early in neonatal life can predict impairments in neuromotor development. However, current techniques to monitor infant movement mainly rely on observer scoring, a technique limited by skill, fatigue, and inter-rater reliability. Consequently, we tested the use of a lightweight, wireless, accelerometer system that measures movement and can be worn by premature babies without interfering with routine care. We hypothesized that this system would be useful in assessing motor activity, in identifying abnormal movement, and in reducing the amount of video that a clinician would need to review for abnormal movements. Ten preterm infants in the NICU were monitored for 1 h using both the accelerometer system and video. A physical therapist trained to recognize cramped-synchronized general movements scored all of the video data by labeling each abnormal movement observed. The parameters of three different computer models were then optimized based on correlating features computed from accelerometer data and the observer’s annotations. The annotations were compared to the model’s prediction on unseen data. The trained observer identified cramped-synchronized general movements in 6 of the 10 infants. The computer models attained between 70% and 90% accuracy when predicting the same observer label for each data point. Our study suggests that mini-accelerometers may prove useful as a clinical tool assessing patterns of movement in preterm infants.

Development of whole body adiposity in preterm infants

The long-term effects of prematurity, early diet and catch-up growth on metabolic risk and body adiposity are of increasing interest to Neonatologists. Poor growth is known to be associated with poorer neuro-developmental outcome but concern exists that increased rates of "catch-up" (or "recovery") growth may be associated with increased adiposity and the later development of metabolic syndrome. In this manuscript we review the published data on body composition in preterm infants, and present new analyses of body adiposity in preterm infants during the 12-15 months of life, and the effect of growth rate (weight gain) on body adiposity. We conclude that although preterm infants have increased adiposity at term corrected age, they generally have lower body fat than their term peers during the rest of the 12-15 months of life. Although more rapid "catch-up" growth in preterm infants during the first year of life is associated with greater body fatness than slower rates of growth, these higher rates of growth lead to body composition more similar to that of the term-born infant, than do slower rates of growth. Although more studies are needed to determine whether these short-term increases or the longer-term decreases in adiposity modify the risk on chronic diseases such as diabetes mellitus, hypertension or other components of the metabolic syndrome, the widely held concern that preterm babies have greater adiposity than their term peers, and that this is worsened by greater amounts of catch-up growth, are not supported by the available evidence.

The effects of varying protein and energy intakes on the growth and body composition of very low birth weight infants

Objective

To determine the effects of high dietary protein and energy intake on the growth and body composition of very low birth weight (VLBW) infants.

Study design

Thirty-eight VLBW infants whose weights were appropriate for their gestational ages were assessed for when they could tolerate oral intake for all their nutritional needs. Thirty-two infants were included in a longitudinal, randomized clinical trial over an approximate 28-day period. One control diet (standard preterm formula, group A, n = 8, 3.7 g/kg/d of protein and 129 kcal/kg/d) and two high-energy and high-protein diets (group B, n = 12, 4.2 g/kg/d and 150 kcal/kg/d; group C, n = 12, 4.7 g/kg/d and 150 kcal/kg/d) were compared. Differences among groups in anthropometry and body composition (measured with bioelectrical impedance analysis) were determined. An enriched breast milk group (n = 6) served as a descriptive reference group.

Results

Groups B and C displayed greater weight gains and higher increases in fat-free mass than group A.

Conclusion

An intake of 150 kcal/kg/d of energy and 4.2 g/kg/d of protein increases fat-free mass accretion in VLBW infants.

Graphical Exploration of Dimensions of Preterm Infant Growth in Weight in Association With Biological, Nutritional, and Energy Expenditure Conditions

The small sample sizes of studies involving preterm infants limit the use of statistics for examination of multivariate conditions contributing to clinically important growth dimensions of weight: rate of weight gain, body composition (fat-free and fat mass), and weight relative to reference infants (z score). The authors used graphical analyses, including multivariate proportional matrix, parallel coordinates, and bivariate plots with regression lines and splines, to explore specific variables derived from a theoretical model of biological, nutritional intake, and energy expenditure conditions influencing growth dimensions. The sample included 28 infants in 4 birth-weight categories: extremely low (<1,000 g), very low/smaller (1,000—1,249 g), very low/larger (1,250—1,499 g), and low (1,500—1,750 g). The authors examined the rate of weight gain before and after nipple feeding initiation. Fat-free mass was estimated with total body water and fetal reference data, and fat mass with skinfold thicknesses. Despite infants achieving the expected rate of weight gain for a fetus of the same postconceptional age, by hospital discharge 13 infants showed growth restriction with weight <10th centile. Infants with respiratory distress syndrome history were highest in negative z-score change from regain of birth weight to discharge, despite higher ordering on protein intake and fat-free mass. Graphical analyses provided visual patterns of distributions and orderings of measures of multiple variables that, taken together, identified potential influencing conditions and raised questions for further study. Other variables, including feeding protocols and practices, infant feeding competence, and health status, may contribute to variability in weight growth dimensions and influence relationships with biologic, nutritional, and energy expenditure conditions.

Maternal perceptions of infant exercise in the neonatal intensive care unit

OBJECTIVE

To identify important factors that influence mothers' perceptions of engaging in exercise with their preterm infants.

DESIGN

Qualitative, semistructured individual interviews.

SETTING

Neonatal Intensive Care Unit.

PARTICIPANTS

Thirteen mothers of preterm infants who were in the Neonatal Intensive Care Unit.

METHODS

Two researchers conducted interviews with mothers in English or Spanish. Interviews were recorded, transcribed, and analyzed.

RESULTS

Mothers tended to view infant exercise as beneficial but feared for the safety of their infants. They perceived nurses as experts who could safely exercise their infants but feared that they themselves might harm their infants. Factors that influenced their beliefs included previous experiences with infant exercise and views regarding the fragility or the strength of their own infants. Mothers identified nurses, doctors, family members, and research studies as trusted sources of information on exercise efficacy and safety.

CONCLUSION

Understanding and addressing mothers' perceptions is a crucial component of a nursing intervention that teaches parents to do assisted exercises at home with their preterm infants.