Preterm infants of lower gestational age at birth have greater waist circumference-length ratio and ponderal index at term age than preterm infants of higher gestational ages

Association of age of initiation and type of complementary foods with body mass index and weight-for-length at 12 months of age in preterm infants

OBJECTIVE

To assess whether in very preterm infants (1) body mass index (BMI) Z-score and weight-for-length (WtFL) Z-score at 1 year of age and (2) head growth from discharge to 1 year are associated with breastfeeding at discharge and the age of onset and type of complementary foods.

STUDY DESIGN

Observational cohort study.

RESULTS

Infants started on only ready-made complementary (RMC) feedings at ≤26 weeks adjusted age had the highest adjusted BMI Z-score and WtFL Z-score at 1 year of age. Adjusted change in fronto-occipital circumference was highest in infants either discharged on breastmilk or receiving home-made complementary food with/without RMC (HMM) at ≤26 weeks adjusted age.

CONCLUSIONS

Infants started on RMC ≤26 weeks adjusted age had the highest BMI Z-score and WtFL Z-score at 1 year. Head growth from discharge to 1 year was highest in infants either discharged on breastmilk or receiving HMM at ≤26 weeks adjusted age.

Maternal chronic stress correlates with serum levels of cortisol, glucose and C-peptide in the fetus, and maternal non chronic stress with fetal growth

INTRODUCTION

During pregnancy, maternal stressors cause changes in both maternal and fetal HPA axes. We therefore investigated the impact of maternal non chronic and chronic stress on fetal glucose metabolism and growth, and serum levels of cortisol in the fetus.

MATERIALS AND METHODS

Normal weight pregnant women (n = 192; mean ± SD 27.9 ± 4.2 years old, and; 26.9 ± 2.4 kg/m²) were assessed during the 2nd and 3rd trimester with anthropometry, fetal ultrasound, blood samples for serum CRH, cortisol and IL6, and STAI trait and state stress questionnaires. We measured serum cortisol, insulin and c-peptide, and plasma glucose from cord blood. Neonates underwent anthropometry at the 3rd post-delivery day.

RESULTS

In both 2nd and 3rd trimesters, women with STAI trait scores ≥40 had significantly greater levels of fasting serum CRH and cortisol than those with STAI trait scores<40. 2nd trimester: STAI trait scores correlated positively with cord blood glucose and c-peptide. Maternal serum CRH correlated negatively with U/S fetal biparietal head diameter, while serum cortisol correlated positively with abdominal circumference. Maternal serum IL6, CRH and cortisol all correlated positively with birth waist circumference. 3rd trimester: Women with STAI state scores ≥40 had fetuses with larger U/S abdominal and smaller head circumferences compared to those of women with STAI scores <40. Women with STAI trait scores ≥40 had greater levels of cord blood cortisol, glucose, and c-peptide compared to women with STAI scores <40. STAI state scores ≥40 correlated positively with maternal CRH and U/S fetal abdominal circumference, and negatively with fetal head circumference and biparietal diameter. STAI trait scores correlated positively with cord blood c-peptide, glucose, insulin and cortisol. Maternal serum levels of CRH correlated positively with U/S fetal abdominal circumference and cord blood cortisol, and negatively with fetal head circumference and biparietal head diameter. Maternal serum levels of both CRH and cortisol correlated positively with cord blood c-peptide, glucose, and insulin. STAI trait was the best positive predictor of cord blood cortisol, glucose and c-peptide, whilst STAI state was the best positive and negative predictor, respectively of fetal abdominal circumference and fetal head circumference or biparietal diameter.

CONCLUSIONS

Increased maternal chronic stress (reflected by the STAI trait score) associates with increased fetal cortisol, glucose, c-peptide secretion and thus, insulin resistance. Maternal non chronic stress (STAI state) in the 3rd trimester associates with changes in fetal growth pattern, including increased and decreased measurements of fetal abdominal and head growth respectively.

Optimizing individual nutrition in preterm very low birth weight infants: double-blinded randomized controlled trial

OBJECTIVE

In preterm neonates fed human milk, fortification may be adjusted by (1) optimization, based on growth rate and serum nutrient analyses, or (2) individualization, based on serial milk nutrient analyses. The primary aim was to determine whether individualized plus optimized nutrition (experimental) improves velocity of weight gain and linear growth from birth to endpoint (36 weeks postmenstrual age or discharge) when compared with optimized nutrition alone (controls).

STUDY DESIGN

Double-blinded parallel group randomized trial in 120 neonates <29 weeks gestational age (GA) or <35 weeks and small for GA (birth weight < 10th centile).

RESULT

Weight-gain velocity (13.1 ± 2.1, n = 57 controls, vs. 13.0 ± 2.6 g kg^-1 day^-1, n = 59 experimental, P = 0.87), linear growth (0.9 ± 0.2, n = 55, vs. 0.9 ± 0.2 cm week^-1, n = 52, P = 0.90) and frequency of weight/length disproportion (2% vs. 2%, P = 0.98) were similar in both groups.

CONCLUSIONS

Individualized plus optimized nutrition does not improve weight gain, linear growth, or weight/length disproportion at endpoint versus optimized nutrition alone.

Updates on Assessment and Monitoring of the Postnatal Growth of Preterm Infants

Assessing and monitoring the physical growth of preterm infants is fundamental to NICU care. The goals of nutritional care are to approximate the growth and body composition of the healthy fetus and to support optimal brain development while minimizing future cardiometabolic risk. Both poor and excessive growth predict adverse long-term health outcomes. Growth curves are clinical tools used to assess the preterm infant's growth status. Several growth curves for preterm infants were developed in the past decade. To use them effectively, clinicians need to understand how each growth curve was developed; the underlying reference population; intended use; and strengths and limitations. Intrauterine growth curves are references that use size at birth to represent healthy fetal growth. These curves serve 2 purposes-to assign size classifications at birth and to monitor postnatal growth. The INTERGROWTH-21 ^st preterm postnatal growth standards were developed to compare the postnatal growth of preterm infants to that of healthy preterm infants rather than the fetus. Individualized weight growth curves account for the water weight loss that frequently occurs after birth. In addition, body mass index (BMI) curves are now available. In this review, we discuss the main characteristics of growth curves used for preterm infants as well as the use of percentiles, z scores, and their change over time to evaluate size and growth status. We also review the differences in body composition between preterm infants at term-equivalent age and term-born infants and the potential role of monitoring proportionality of growth using BMI curves.

Longitudinal growth changes from birth to 8-9 years in preterm and full term births

BACKGROUND

The aim of this study is to assess the effect of age at adiposity rebound (AR) and changes in growth between birth and 6 months on growth status at 8-9 years in children born term and preterm. Age at AR is inversely correlated with risk for later obesity in children born full term, but has not been analyzed in children born preterm.

METHODS

Birth anthropometrics, and weight and length/height data from age 6 months through 8-9 years were recorded for 175 children born in 2008 in the military health system. Calculated variables include body mass index (BMI, kg/m2), Z-scores, and age at AR.

RESULTS

Age at AR could be calculated for 150 children (32% preterm); average age was 5.4 years and 5.3 years for children born term and preterm, respectively (NS). For children born term and preterm, there was a significant correlation between younger age at AR and higher BMI Z-score at 8-9 years (r = - 0.685), and a direct relationship between weight Z-score change from birth to 6 months and weight Z-scores at 8-9 years (p = 0.034).

CONCLUSIONS

Younger age at AR correlates with higher BMI Z-score at 8-9 years in children born both term and preterm. Weight gain from birth to 6 months correlates with weight Z-score at 8-9 years. These results emphasize the importance of younger age at AR in addition to greater early weight gain as an indicator of later obesity.

Reference Values for Abdominal Circumference in Premature Infants

Objectives: Abdominal distention is a common indicator of feeding intolerance in premature newborns. In the absence of a precise definition, abdominal distention and its degree are highly subjective. The aim of this study was to construct references and smoothed percentiles for abdominal circumference (AC) and AC to head circumference (HC) ratio (AC/HC) in infants born between 24 weeks and 34 weeks of gestational age. Methods: ACs and HCs were collected weekly in eutrophic premature infants without congenital abdominal or cerebral malformation. AC and HC charts were modeled using the LMS method, excluding measures associated with abdominal distention at clinical examination or intracranial abnormality at cerebral ultrasounds. Changes in AC and AC/HC over time were studied by repeated-measures analysis using mixed-effects linear models. Results: A total of 1,605 measurements were made in 373 newborns with a mean gestational age of 31 [29-33] weeks and mean birth weight of 1,540 [1,160-1,968] g. Of these measurements, 1,220 were performed in normal conditions. Gestational age, postnatal age, singleton status, and respiratory support were significantly associated with AC and AC/HC. LMS curves were generated according to gestational age groups and postnatal age, with coherent profiles. AC/HC was 0.91 [0.86-0.95] in absence of abdominal distention. It was higher in cases of abdominal distention (0.95 [0.89-1.00], p < 0.001) and necrotizing enterocolitis (0.98 [0.93-1.07], p < 0.001). Conclusions: References constructed for AC and AC/HC might be used to assess feeding tolerance in premature infants. AC/HC was more relevant than AC to rationalize the diagnosis of abdominal distention.

Cohort study showed that growth rate increment has not been enough to prevent growth retardation of preterm infants and raised concerns about unbalanced growth

AIM

We describe the postnatal weight gain, linear and head growth trends of surviving preterm infants from 2005 to 2017.

METHODS

Multicentre cohort study, including surviving preterm infants <32 weeks (n = 21 084), from the Spanish Neonatal Network database, without major congenital malformations who were less than 50 weeks postmenstrual age at discharge. Outcomes were weight gain (g/kg/day), linear and head growth (cm/week) and changes in weight, length and head circumference z-scores from birth to discharge. The study period was divided into 2005-8, 2009-11, 2012-14 and 2015-17.

RESULTS

Weight gain, linear growth and head growth were slightly higher in 2015-2017 than in 2005-2008: 12.2 ± 2.6 to 13.1 ± 2.5 g/kg/day, 0.98 ± 0.6 to 1.03 ± 0.6 cm/week and 0.76 ± 0.2 to 0.77 ± 0.3 cm/week, respectively. It was associated with a decreased fall in weigh, length and head circumference z-scores from birth to discharge (-1.32 ± 0.9 to -1.01 ± 0.84, -1.38 ± 1.2 to -1.18 ± 1.2 and -0.41 ± 1.2 to -0.33 ± 1.3, respectively).

CONCLUSION

Postnatal growth restriction remained a common complication of prematurity despite some increment over the last years. Growth disproportionality seemed to be worsening as weight gain was increased more than linear growth.

Adjustable feedings plus accurate serial length measurements decrease discharge weight-length disproportion in very preterm infants: quality improvement project

BACKGROUND

Preterm very-low-birth-weight (≤1500 g) infants exhibit disproportionate weight-for-length growth in the Neonatal Intensive Care Unit.

LOCAL PROBLEM

High frequency of body mass index (BMI) > 90th centile at discharge and 1-year postnatal age associated with elevated blood pressure and serum leptin in infancy and adolescence.

METHODS

Single-institution quality improvement project in appropriately grown infants born at 23^0/7-28^6/7 weeks gestational age and discharged home.

INTERVENTION

Adjustable feeding protocol based on valid serial length measurements (board or caliper).

RESULTS

The average monthly percentage of weight-for-length disproportion at discharge decreased from 13% in Epoch 1 to 0% in Epoch 2 (P < 0.05). Although the average Z-score for BMI at discharge was lower in Epoch 2 versus Epoch 1 (P < 0.01), this was absent by 1 year follow-up (P = 0.91).

CONCLUSIONS

Adjustable feedings plus use of accurate serial length measurements decreases weight-for-length disproportion at hospital discharge but not at 1 year.

BMI Is a Better Body Proportionality Measure than the Ponderal Index and Weight-for-Length for Preterm Infants

BACKGROUND

Clinicians have observed preterm infants in the neonatal intensive care unit growing disproportionally; however, the only growth charts that have been available were from preterm infants born in the 1950s which utilized the ponderal index. Prior to creating the recently published BMI curves, we found only 1 reference justifying the use of the ponderal index.

OBJECTIVES

To determine the best measure of body proportionality for assessing growth in US preterm infants.

METHODS

Using a dataset of 391,681 infants, we determined the body proportionality measure that was most correlated with weight and least correlated with length. We examined the sex-specific overall correlations and then stratified further by gestational age (GA). We then plotted the body proportionality measures versus length to visualize apparent discrepancies in the appropriate measure.

RESULTS

The overall correlations showed weight/length3 (ponderal index) was the best measure but stratification by GA indicated that BMI (weight/length2) was the best measure. This seeming inconsistency was due to negative correlations between ponderal index and length at each GA. BMI, on the other hand, had a correlation with length across GAs, but was uncorrelated with length within GAs. Both ponderal index and BMI were positively correlated with weight.

CONCLUSIONS

BMI is the appropriate measure of body proportionality for preterm infants, contrary to current practice.

Anthropometric trends from 1997 to 2012 in infants born at ⩽28 weeks' gestation or less

OBJECTIVE

Postnatal growth failure is common after preterm birth, in particular for infants born at ⩽28 weeks' gestation, but it is unknown if growth-to-term equivalent age has improved over the years as neonatal intensive care in general, and infant nutrition in particular, have improved. The objective of the study was to evaluate anthropometric trends at NICU discharge for infants born at ⩽28 weeks' gestation using a large national database.

STUDY DESIGN

Analysis of growth in weight, length, head circumference and body mass index (kg m²) in 23 005 infants born in 1997 to 2012 who survived to neonatal intensive care unit discharge at ⩽41 weeks' postmenstrual age.

RESULTS

Discharge weight, length, head circumference and body mass index were converted to Z-scores using a reference database, and growth trends over the 16 years were summarized. Discharge results also were summarized for common neonatal morbidities, including chronic lung disease. Gestational age at birth and postmenstrual age at discharge were similar across the 16 years. Discharge weight, length and head circumference Z-scores were all below the median, but head circumference Z-scores consistently were closer to the median than were weight and length. In 1997 compared with 2012, the weight Z-score improved from -1.5 to -0.6; the length Z-score increased the least, from -1.68 to just -1.16; the head circumference Z-score improved from -0.68 to -0.30; and the body mass index Z-score increased from -0.66 to 0.19. Percent small-for-gestational age at birth was stable across the years at 8.4 to 9.3%, and the frequency of postnatal growth failure at discharge improved from 55.4% in 1997 to 19.6% in 2012.

CONCLUSIONS

Growth-to-discharge progressively improved from 1997 to 2012, but Z-scores remained below the reference median for weight, length and head circumference. Length Z-scores were consistently significantly less than for weight, and body mass index Z-scores have been above the reference median since 2002. Prospective studies are needed to quantify anthropometric trends in relation to body composition and to current nutritional strategies.

The clinical utility of anthropometric measures to assess adiposity in a cohort of prematurely born infants: Correlations with MRI fat quantification

OBJECTIVE

To correlate magnetic resonance imaging (MRI) of body fat in preterm infants at the time of hospital discharge with same-day anthropometric measures, and to assess the clinical utility of body mass index (BMI), waist circumference (WC), and WC/length ratio as indicators of visceral fat.

STUDY DESIGN

MRI performed prior to NICU discharge in 25 infants born preterm at <32 weeks gestation. Total body fat and visceral fat were quantified using a commercial software program. The Pearson correlation coefficient (r, 95% C.I.) was used to describe strength of association between MRI fat and anthropometric measures.

RESULTS

BMI and weight at discharge were strongly correlated with total body fat (r = 0.95 and 0.89 respectively; p < 0.001). Total body fat as a % of body weight was moderately correlated with weight (r = 0.53), WC (r = 0.52), and BMI (r = 0.47). Weight, BMI, and ponderal index all were found to correlate with total visceral fat (r = 0.65, 0.64, 0.55 respectively) but WC did not (r = 0.28). WC/length ratio was not correlated with any MRI fat measurements.

CONCLUSIONS

BMI and weight at discharge both correlate with MRI fat measurements. Our findings do not support the usefulness of measuring WC or WC/length ratio in preterm infants at term-equivalent age.

Measurement of abdominal circumference in preterm infants

BACKGROUND

Body weight, length and head and thoracic circumference are routinely measured in obstetric and neonatal departments. Reference values for these measurements have been established for the neonatal population. Neonatal abdominal circumference is not routinely measured, and no reference values for this measurement have been determined. To evaluate the increase in abdominal circumference in newborns with abdominal pathology such as necrotizing enterocolitis, information about normal abdominal circumference in healthy neonates shortly after birth is needed. The aim of this study was to determine the correlation between abdominal circumference and birth weight by measuring the abdominal circumference of premature neonates soon after birth.

METHODS

Abdominal circumference was measured within 30 min of birth in 220 neonates born between 23 and 35 weeks' gestation.

RESULTS

There was no statistically significant difference in abdominal circumference between boys and girls in the study population. A specific formula for estimating normal abdominal circumference was developed: y = 0.0053x + 14.83 (y = abdominal circumference in cm; x = body weight in g; 0.0053 = regression coefficient; 14.83 = regression constant).

CONCLUSION

A positive linear correlation between abdominal circumference and birth weight was found in infants at birth. The correlation can be summarized as a linear regression equation. Further studies are needed to investigate possible factors associated with abdominal circumference in fed versus unfed preterm infants.

Nutritional support for premature infants in the neonatal intensive care unit

Nutritional support for premature infants in the neonatal intensive care unit setting is complex. Such infants have conditions unique to this period of the lifespan requiring specialized care management, both of which may impede the provision of adequate nutrition to support basal metabolic needs. Premature infants require optimum nutritional intake to support rapid growth during a time when they are not fully capable of tolerating it. This article reviews developmental anatomy, physiology, and the effect of premature delivery by systems; the challenges of providing adequate nutrition; and current evidence-based strategies to provide nutrition for premature infants during hospitalization.

Trajectories of length, weight, and bone mineral density among preterm infants during the first 12 months of corrected age in China

Background

Limited evidence has been provided on the trajectories of length, weight, and bone mineral density (BMD) among preterm infants in early life in Asian countries.

Methods

We conducted a longitudinal study, which included 652 late preterm (gestational age: 34–36.9 weeks), 486 moderate preterm (32–33.9), 291 very preterm (28–31.9), 149 extremely preterm infants (≤28.9) and 1434 full-term peers (≥37) during the first 12 months of corrected age in Wuhan, China. Weight and length were measured at birth, once randomly before term, and every month thereafter. BMD was examined at 3, 6, 9 and 12 months using dual-energy X-ray absorptiometry.

Results

From birth to 12 months of corrected age, growth peaks in length and weight were observed at 1–3 months among preterm infants. No catch-up growth in length, weight, and BMD was observed among preterm infants. However, accelerated growth in length, weight, and BMD was found. Among extremely preterm infants, relative to full-term infants, length was −6.77 cm (95 % CI: −7.14, −6.40; P for trend < 0.001) lower during the first 12 months; weight was −1.23 kg (−1.33, −1.13; P for trend < 0.001) lower; and BMD was −0.070 g/cm²(−0.087, −0.053; P for trend < 0.001) lower; however, average growth rates of these measures were higher (Ps < 0.05). Small gestational age and low birth weight were independently associated with lower length, weight, and BMD.

Conclusion

Growth peaks in length and weight among preterm infants were observed at 1–3 months. No catch-up growth in length, weight, and BMD was observed, however, there was accelerated growth in length, weight, and BMD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-015-0396-6) contains supplementary material, which is available to authorized users.

BMI curves for preterm infants

BACKGROUND AND OBJECTIVES

Preterm infants experience disproportionate growth failure postnatally and may be large weight for length despite being small weight for age by hospital discharge. The objective of this study was to create and validate intrauterine weight-for-length growth curves using the contemporary, large, racially diverse US birth parameters sample used to create the Olsen weight-, length-, and head-circumference-for-age curves.

METHODS

Data from 391 681 US infants (Pediatrix Medical Group) born at 22 to 42 weeks' gestational age (born in 1998-2006) included birth weight, length, and head circumference, estimated gestational age, and gender. Separate subsamples were used to create and validate curves. Established methods were used to determine the weight-for-length ratio that was most highly correlated with weight and uncorrelated with length. Final smoothed percentile curves (3rd to 97th) were created by the Lambda Mu Sigma (LMS) method. The validation sample was used to confirm results.

RESULTS

The final sample included 254 454 singleton infants (57.2% male) who survived to discharge. BMI was the best overall weight-for-length ratio for both genders and a majority of gestational ages. Gender-specific BMI-for-age curves were created (n = 127 446) and successfully validated (n = 126 988). Mean z scores for the validation sample were ∼0 (∼1 SD).

CONCLUSIONS

BMI was different across gender and gestational age. We provide a set of validated reference curves (gender-specific) to track changes in BMI for prematurely born infants cared for in the NICU for use with weight-, length-, and head-circumference-for-age intrauterine growth curves.

Fetal programming, epigenetics, and adult onset disease

How early life events program adult disease is undergoing a transition from the broad field of maternal malnutrition to the current relevant issues of food deserts and prematurity. Although many adult diseases and morbidities associate with various early life events and programming, the morbidities of insulin resistance, cardiovascular disease, and obesity seem to be common end points of many early life events despite potential confounders.

Neonatal birth waist is positively predicted by second trimester maternal active ghrelin, a pro-appetite hormone, and negatively associated with third trimester maternal leptin, a pro-satiety hormone

INTRODUCTION

In pregnancy physiological mechanisms activated by maternal appetite contribute to adequate energy intake for the mother and for the fetus. The role of maternal appetite-related peptides and their possible association with neonatal energy stores and glucose metabolism have not been investigated as yet. The aim was to investigate, during pregnancy, the association of fasting maternal appetite-related hormones levels [ghrelin (active), GLP1 (active), total PYY and leptin] with neonatal waist, percent total body fat and insulin levels at birth.

METHODS

Forty-two normal and thirty eight overweight women (mean±SD; age: 26.9±2.5years; pre-pregnancy BMI 26±2.2kg/m(2)) were seen during each of the three trimesters, had blood sampling and a 75g oral glucose tolerance test. At birth, neonates underwent anthropometry and cord blood sampling for c-peptide, glucose, insulin.

RESULTS

During all three trimesters maternal weight correlated positively with percent total neonatal body fat while during the second and third trimesters it correlated positively with birth weight. The second trimester maternal active ghrelin levels correlated positively with neonatal waist and were its best positive predictor. The third trimester maternal active ghrelin levels correlated positively with neonatal waist and negatively with percent total neonatal body fat, fetal cord blood insulin levels and were the best negative predictor of the latter. The third trimester maternal leptin levels correlated negatively with neonatal waist.

CONCLUSIONS

During pregnancy circulating maternal active ghrelin, a pro-appetite hormone, is associated with neonatal visceral energy storage (as expressed by neonatal waist). By inhibiting glucose-driven maternal insulin secretion, ghrelin might ensure adequate fasting glucose and nutrient supplies to the fetus while limiting overall fetal adipose tissue deposition.

Assessment of neonatal growth in prematurely born infants

The concept that adequate nutritional status and normal growth are important is well-accepted. How to assess the adequacy of nutrition and how to define appropriate growth remains an area of active debate. Our goal is to review how growth is assessed at birth and during the hospital stay of prematurely born infants, and to offer a standardized approach.

Prematurity is not associated with intra-abdominal adiposity in 5- to 7-year-old children

OBJECTIVE

To compare body composition and abdominal fat partitioning between 5- to 7-year old children born preterm and born at term. We hypothesized children born preterm to have a higher body fat percentage and higher percentage of intra-abdominal adipose tissue (%IAAT) compared with their peers born at term.

STUDY DESIGN

A total of 236 children aged 5-7 years, ie, 116 children born preterm (gestational age 29.8 ± 2.6 [30; 24-33] weeks [mean ± SD {median; range}]) and 120 children born at term were included. Body composition was measured by bioelectrical impedance analysis and %IAAT by magnetic resonance imaging. Body mass index, skin fold thickness, and waist-to-hip ratio were investigated as further measures of body composition. Dietary records were compared between both groups.

RESULTS

Children born preterm were shorter (120 cm vs 123 cm, P < .001), lighter (21.8 kg vs 24.3 kg, P < .001), and had a lower body mass index (15.1 kg/m(2) vs 15.9 kg/m(2), P = .003) compared with controls. There were no differences in %IAAT (n = 154), and body fat mass although energy uptake was higher in preterms (335 kJ/kg/d vs 302 kJ/kg/d, P = .03).

CONCLUSIONS

At the age of 5-7 years, children born preterm showed neither increased fat mass nor intra-abdominal adiposity.

Novel noninvasive anthropometric measure in preterm and full-term infants: normative values for waist circumference:length ratio at birth

BACKGROUND

Waist circumference:length ratio (WLR) and ponderal index (PI) appear to be useful markers of visceral and total adiposity, respectively. However, there are no normative birth data across the full range of gestational ages.

METHODS

In this retrospective cohort study of 500 preterm and 1,426 full-term infants, born in 1998 and 2008 at three military hospitals, the percentile growth curves for WLR and PI were calculated. There were no sex differences, and results were combined to obtain values from 26 to 42 wk gestation.

RESULTS

Between 26 and 42 wk gestation, median birth WLR increased from 0.55 to 0.62, and median PI increased from 21.1 to 25.6. The adjusted mean WLR at birth among infants born <34 wk increased from 0.55 in 1998 to 0.58 in 2008 (P = 0.048), suggesting that early-preterm infants born in 2008 had greater abdominal adiposity than those born in 1998.

CONCLUSION

We report normative birth data for WLR and PI in preterm and full-term infants by gestational age and sex. WLR and PI may be useful as clinical markers of visceral and overall adiposity. In conjunction with other anthropometric measures, WLR and PI may be useful to monitor postnatal nutrition and growth and assess risk for later obesity and cardiometabolic disorders.