Composition of postnatal weight loss and subsequent weight gain in small for dates newborn infants

Development of an imputation model to recalibrate birth weights measured in the early neonatal period to time at delivery and assessment of its impact on size-for-gestational age and low birthweight prevalence estimates: a secondary analysis of a pregnancy cohort in rural Nepal

OBJECTIVES

In low-income countries, birth weights for home deliveries are often measured at the nadir when babies may lose up of 10% of their birth weight, biasing estimates of small-for-gestational age (SGA) and low birth weight (LBW). We aimed to develop an imputation model that predicts the 'true' birth weight at time of delivery.

DESIGN

We developed and applied a model that recalibrates weights measured in the early neonatal period to time=0 at delivery and uses those recalibrated birth weights to impute missing birth weights.

SETTING

This is a secondary analysis of pregnancy cohort data from two studies in Sarlahi district, Nepal.

PARTICIPANTS

The participants are 457 babies with daily weights measured in the first 10 days of life from a subsample of a larger clinical trial on chlorhexidine (CHX) neonatal skin cleansing and 31 116 babies followed through the neonatal period to test the impact of neonatal massage oil type (Nepal Oil Massage Study (NOMS)).

OUTCOME MEASURES

We developed an empirical Bayes model of early neonatal weight change using CHX trial longitudinal data and applied it to the NOMS dataset to recalibrate and then impute birth weight at delivery. The outcomes are size-for-gestational age and LBW.

RESULTS

When using the imputed birth weights, the proportion of SGA is reduced from 49% (95% CI: 48% to 49%) to 44% (95% CI: 43% to 44%). Low birth weight is reduced from 30% (95% CI: 30% to 31%) to 27% (95% CI: 26% to 27%). The proportion of babies born large-for-gestational age increased from 4% (95% CI: 4% to 4%) to 5% (95% CI: 5% to 5%).

CONCLUSIONS

Using weights measured around the nadir overestimates the prevalence of SGA and LBW. Studies in low-income settings with high levels of home births should consider a similar recalibration and imputation model to generate more accurate population estimates of small and vulnerable newborns.

Breastfeeding and neonatal weight loss in healthy term infants

BACKGROUND

Neonatal weight loss is universally recognized, yet poorly understood. Limited professional consensus exists on the definition of lower limit of safe weight loss.

OBJECTIVE

Our aim was to assess the extent of neonatal weight loss and its association with selected clinical variables in a population of healthy term infants cared for using a specific protocol on weight loss.

METHODS

We retrospectively considered 1003 infants consecutively admitted to the regular nursery of the Institute for Maternal and Child Health "Burlo Garofolo" (Trieste, Italy). We studied the relationship of selected variables with neonatal weight loss recorded during the hospital stay. We also analyzed all readmissions in the first month of life as a result of weight loss and its complications.

RESULTS

We observed a mean absolute weight loss of 228 g ± 83g, and a mean percent weight loss of 6.7% ± 2.2%. Weight loss ≥ 10% and > 12% were 6% and 0.3%, respectively. In multivariate logistic regression, cesarean section, hot season, any formula feeding, and jaundice not requiring phototherapy were independently associated with neonatal weight loss ≥ 8%. Conversely, low gestational age status was associated with lower weight loss. Readmission within the first month of life because of dehydration occurred in 0.3% of infants.

CONCLUSIONS

Breastfeeding, compared to formula feeding, may not be a risk factor for greater early neonatal weight loss, at least in contexts in which weight is routinely monitored, breastfeeding is repeatedly assessed and appropriately supported, and careful supplementation is prescribed to limit and promptly treat excess weight loss and its related complications.

The effects of delivery route and anesthesia type on early postnatal weight loss in newborns: the role of vasoactive hormones

OBJECTIVE

To investigate the effects of delivery route and maternal anesthesia type and the roles of vasoactive hormones on early postnatal weight loss in term newborns.

METHODS

Ninety-four term infants delivered vaginally (group 1, n=31), cesarean section (C/S) with general anesthesia (GA) (group 2, n=29), and C/S with epidural anesthesia (EA) (group 3, n=34) were included in this study. All infants were weighed at birth and on the second day of life and intravenous (IV) fluid infused to the mothers for the last 6 h prior to delivery was recorded. Serum electrolytes, osmolality, N-terminal proANP (NT-proANP), brain natriuretic peptide (BNP), aldosterone and plasma antidiuretic hormone (ADH) concentrations were measured at cord blood and on the second day of life.

RESULTS

Our research showed that postnatal weight loss of infants was higher in C/S than vaginal deliveries (5.7% vs. 1.3%) (p < 0.0001) and in EA group than GA group (6.8% vs. 4.3%) (p < 0.0001). Postnatal weight losses were correlated with IV fluid volume infused to the mothers for the last 6 h prior to delivery (R = 0.814, p = 0.000) and with serum NT-proANP (R = 0.418, p = 0.000), BNP (R = 0.454, p = 0.000), and ADH (R = 0.509, p = 0.000) but not with aldosterone concentrations (p > 0.05).

CONCLUSION

Large amounts of IV fluid given to the mothers who were applied EA prior to the delivery affect their offsprings' postnatal weight loss via certain vasoactive hormones.

Impact of neonatal protein metabolism and nutrition on screening for phenylketonuria

OBJECTIVES

Early blood phenylalanine (Phe) elevation after birth enables screening for and anticipation of the diagnosis of phenylketonuria. The differential impact of factors involved in this phenomenon, however, has not been elucidated. To solve this question, phenotype, genotype, dietary Phe intake, timing of blood collection, and Phe metabolism were retrospectively analyzed in 21 phenylketonuria newborns and prospectively in 1.

PATIENTS AND METHODS

Patients were assigned to 1 of 4 classes of phenylalanine hydroxylase (PAH) deficiency (severe, moderate, mild, and benign) on the basis of their Phe tolerance. Phe ingested, tolerated, and released from endogenous catabolism was assessed.

RESULTS

From birth to screening test, the amount of Phe tolerated ranged from 704 to 1620 mg, according to the class of PAH deficiency. The amount of Phe ingested ranged only from 204 to 405 mg, whereas the endogenous Phe breakdown ranged from 812 to 1534 mg, resulting in a rate of Phe catabolism ranging from 262 to 341 mg/day, regardless of the class of PAH deficiency.

CONCLUSIONS

The high rate of protein catabolism is the main determinant of neonatal hyperphenylalaninemia. It is sufficient to turn to positive the screening test in severe and moderate PAH deficiency. In mild and benign PAH deficiency, the outcome of screening procedures can be substantially altered by the concurrence of genetic and peristaltic factors. These results imply that the value of blood Phe at the screening test is not fully predictive of the phenylketonuria phenotype, and strengthen concerns regarding the reliability of early screening procedures.

Association between early postnatal weight loss and death or BPD in small and appropriate for gestational age extremely low-birth-weight infants

OBJECTIVE

To examine the association between weight loss during the first 10 days of life and the incidence of death or bronchopulmonary dysplasia (BPD) in small for gestational age (SGA) and appropriate for gestational age (AGA) extremely low-birth-weight infants.

DESIGN/METHODS

This is a retrospective analysis of a cohort of ELBW (birth weight <1000 g) infants from the NICHD Neonatal Research Network's database. The cohort consisted of 9461 ELBW infants with gestational age of 24-29 weeks, admitted to Network's participating centers during calendar years 1994-2002 and surviving at least 72 h after birth. The cohort was divided into two groups, 1248 SGA (with birth weight below 10th percentile for gestational age) and 8213 AGA (with birth weight between 10th and 90th percentile) infants. We identified infants with or without weight loss during the first 10 days of life, which we termed as 'early postnatal weight loss' (EPWL). Univariate analyses were used to predict whether EPWL was related to the primary outcome, death or BPD, within each birth weight/gestation category (SGA or AGA). BPD and death were also analyzed separately in relation to EPWL. Logistic regression analysis was done to evaluate the risk of death or BPD in SGA and AGA groups, controlling for maternal and neonatal demographic and clinical factors found to be significant by univariate analysis.

RESULTS

SGA ELBW infants had a lower prevalence of EPWL as compared with AGA ELBW infants (81.2 vs 93.7%, respectively, P<0.001). In AGA infants, univariate analysis showed that death or BPD rate was lower in the group of infants with EPWL compared with infants without EPWL (53.4 vs 74.3%, respectively, P<0.001). The BPD (47.2 vs 64%, P<0.001) and death (13.8 vs 32.9%, P<0.001) rate were similarly lower in the EPWL group. The risk-adjusted odds ratios (ORs) showed that EPWL was associated with lower rate of death or BPD (OR 0.47, 95% CI: 0.37-0.60). In SGA infants, on univariate analysis, a similar association between EPWL and outcomes was seen as shown in AGA infants: death or BPD (55.9 vs 75.2%, P<0.001), BPD rate (48.3 vs 62.1%, P=0.002) and rate death (19 vs 40.8%, P<0.001) for those with or without EPWL, respectively. Multiple logistic regression showed that as in AGA ELBW infants, EPWL was associated with lower risk for death or BPD (OR 0.60, 95% CI: 0.41-0.89) among SGA infants.

CONCLUSIONS

SGA infants experienced less EPWL when compared with their AGA counterparts. EPWL was associated with a lower risk of death or BPD in both ELBW AGA and SGA infants. These data suggest that clinicians who consider the association between EPWL and risk of death or BPD should do so independent of gestation/birth weight status.

Birth weight categorization according to gestational age does not reflect percentage body fat in term and preterm newborns

This study was performed to prove the applicability of the small-for-gestational age (SGA), appropriate-for-gestational age (AGA), and large-for-gestational age (LGA) classification depending on birth weight to predict percentage body fat (%BF) measured by dual-energy X-ray absorptiometry (DXA) in term and preterm infants. The data of 159 healthy term and preterm neonates (87 boys and 72 girls) with a gestational age at delivery of 38.4 weeks from two longitudinal studies were analyzed. Anthropometry and body composition data were assessed within the first 10 days after birth. Correlations between anthropometric parameters and fat mass measured by DXA were calculated. Prevalences of observations with low, middle, and high %BF measured by DXA were compared between SGA, AGA, and LGA groups, according to sex and gestational age. In term infants, 42.9% of the newborns with less than 10% body fat were classified to be AGA; 9.9% of all AGA newborns had less than 10% body fat. For the whole group, among the ratios investigated, the weight-length ratio (r=0.82) showed the best correlation to fat mass measured by DXA. The %BF at the time of study was higher in girls (14.75%) than in boys (11.95%). In conclusion, traditional classification based on birth weight centiles does not reflect %BF in term and preterm newborns.

Nutrient requirements for preterm infant formulas

Achieving appropriate growth and nutrient accretion of preterm and low birth weight (LBW) infants is often difficult during hospitalization because of metabolic and gastrointestinal immaturity and other complicating medical conditions. Advances in the care of preterm-LBW infants, including improved nutrition, have reduced mortality rates for these infants from 9.6 to 6.2% from 1983 to 1997. The Food and Drug Administration (FDA) has responsibility for ensuring the safety and nutritional quality of infant formulas based on current scientific knowledge. Consequently, under FDA contract, an ad hoc Expert Panel was convened by the Life Sciences Research Office of the American Society for Nutritional Sciences to make recommendations for the nutrient content of formulas for preterm-LBW infants based on current scientific knowledge and expert opinion. Recommendations were developed from different criteria than that used for recommendations for term infant formula. To ensure nutrient adequacy, the Panel considered intrauterine accretion rate, organ development, factorial estimates of requirements, nutrient interactions and supplemental feeding studies. Consideration was also given to long-term developmental outcome. Some recommendations were based on current use in domestic preterm formula. Included were recommendations for nutrients not required in formula for term infants such as lactose and arginine. Recommendations, examples, and sample calculations were based on a 1000 g preterm infant consuming 120 kcal/kg and 150 mL/d of an 810 kcal/L formula. A summary of recommendations for energy and 45 nutrient components of enteral formulas for preterm-LBW infants are presented. Recommendations for five nutrient:nutrient ratios are also presented. In addition, critical areas for future research on the nutritional requirements specific for preterm-LBW infants are identified.

Determination of nutritional requirements in preterm infants, with special reference to 'catch-up' growth

The usual recommendation for feeding preterm infants is to provide sufficient nutrients to support rates of growth and nutrient accretion equal to intrauterine rates. However, most preterm infants don't tolerate feedings immediately and, therefore, incur significant deficits prior to achieving sufficient intake to support growth. Furthermore, unless they receive nutrient intakes in excess of those usually recommended, they will be smaller than a fetus of the same postmenstrual age at discharge and remain smaller for some time thereafter. The consequences of these early deficits are not known with certainty but there is some evidence that they should be repleted as soon as possible. This requires a redefinition of requirements to include those for both normal growth and catch-up growth. Strategies for doing so include: more aggressive early parenteral nutrition to reduce the magnitude of early losses; greater enteral intakes of protein, and, perhaps, other nutrients once enteral feedings are tolerated; and more attention to nutrition post-discharge. Of these, the latter is somewhat problematic. This is because there seems to be a finite period - perhaps as brief as a few weeks - during which response to increased nutrient intake occurs. Firm data are limited, but those available suggest that current nutritional management of preterm infants can be improved. Whether this will have long-term benefits remains to be determined.

Body water content of extremely preterm infants at birth

BACKGROUND

Preterm birth is often associated with impaired growth. Small for gestational age status confers additional risk.

AIM

To determine the body water content of appropriately grown (AGA) and small for gestational age (SGA) preterm infants in order to provide a baseline for longitudinal studies of growth after preterm birth.

METHODS

All infants born at the Hammersmith and Queen Charlotte's Hospitals between 25 and 30 weeks gestational age were eligible for entry into the study. Informed parental consent was obtained as soon after delivery as possible, after which the extracellular fluid content was determined by bromide dilution and total body water by H(2)(18)O dilution.

RESULTS

Forty two preterm infants were studied. SGA infants had a significantly higher body water content than AGA infants (906 (833-954) and 844 (637-958) ml/kg respectively; median (range); p = 0.019). There were no differences in extracellular and intracellular fluid volumes, nor in the ratio of extracellular to intracellular fluid. Estimates of relative adiposity suggest a body fat content of about 7% in AGA infants, assuming negligible fat content in SGA infants and lean body tissue hydration to be equivalent in the two groups.

CONCLUSIONS

Novel values for the body water composition of the SGA preterm infant at 25-30 weeks gestation are presented. The data do not support the view that SGA infants have extracellular dehydration, nor is their regulation of body water impaired.

Randomised controlled trial of postnatal sodium supplementation on body composition in 25 to 30 week gestational age infants

AIMS

To compare the effects of early and delayed sodium supplementation on body composition and body water compartments during the first two weeks of postnatal life.

METHODS

Preterm infants of 25-30 weeks' gestation were stratified and randomly assigned according to gender and gestational age, to receive a sodium intake of 4 mmol/kg/day beginning either on the second day after birth or when weight loss of 6% of birthweight had been achieved. Daily sodium intake, total fluid intake, energy intake, urine volume, and urinary sodium excretion were recorded. Total body water was measured by H(2)(18)O dilution on days 1, 7, and 14, and extracellular fluid volume by sodium bromide dilution on days 1 and 14.

RESULTS

Twenty four infants received early, and 22 delayed, sodium supplementation. There were no significant differences between the groups in body water compartments on day 1. In the delayed group, but not the early group, there was a significant loss of total body water during the first week (delayed -44 ml/kg, p=0. 048; early 6 ml/kg, p=0.970). By day 14 the delayed, but not the early group, also had a significant reduction in extracellular fluid volume (delayed -53 ml/kg, p=0.01; early -37 ml/kg, p=0.2). These changes resulted in a significant alteration in body composition at the end of the first week (total body weight: delayed 791 ml/kg; early 849 ml/kg, p=0.013). By day 14 there were once again no significant differences in body composition between the two groups.

CONCLUSIONS

Body composition after preterm birth is influenced by the timing of introduction of routine sodium supplements. Early sodium supplementation can delay the physiological loss of body water that is part of normal postnatal adaptation. This is likely to be of particular relevance to babies with respiratory distress syndrome. A tailored approach to clinical management, delaying the introduction of routine sodium supplements until there has been postnatal loss of body water, is recommended.

Influence of respiratory distress syndrome on body composition after preterm birth

AIM

To observe changes in body composition during the first week after birth, in preterm neonates with and without respiratory distress syndrome (RDS), so as to be able to provide optimal fluid and energy intake.

METHODS

Twenty four babies with RDS and 19 healthy preterm babies, with gestational ages ranging from 26-36 weeks, were studied daily for the first week after birth. Total body water (TBW) was measured using bioelectrical impedance analysis. The babies were weighed daily and a record made of fluid and energy intake. Body solids were calculated as the difference between body weight and TBW.

RESULTS

There was a highly significant reduction in body weight by the end of the week, with the RDS babies losing more than the healthy babies (RDS 7.6%; non-RDS 3.7%). There was no significant difference in the amount of TBW at birth in the babies with and without RDS (RDS 85.1%; non-RDS 85.5%) and both groups lost the same amount of body water (RDS 10.9%; non-RDS 9.9%) by the end of the first week. The amount of total body water lost was unrelated to the volume of fluid administered. There was a loss of body solids during the first day in the RDS group, but, overall, there was a highly significant increase in both groups between birth and day 7, which was greater in the healthy babies (RDS 13.0%; non-RDS 42.7%).

CONCLUSIONS

Loss of body water after birth occurs to the same extent in healthy preterm neonates and in babies with RDS and is unrelated to the volume of fluid administered. Given adequate nutritional support, an increase in body solids can accompany early postnatal weight loss and begins almost immediately after birth, in both healthy preterm babies and babies with RDS.

Measurement of transepidermal water loss in Tanzanian cot-nursed neonates and its relation to postnatal weight loss

In healthy cot-nursed Tanzanian neonates (n = 92, gestation 26-42 weeks) measurements of trans-epidermal water loss (TEWL) and weight change were performed during the first 24 h after birth at an average ambient humidity of 70% and an environmental temperature of 32 degrees C. Urine production on day 1 (ml/kg per 24 h) was documented for a subgroup of 13 preterm and 8 term infants. In a limited group of preterm infants (n = 5) TEWL measurements, weight and 24 h urine volume measurements were repeated daily for 7 days. Maximum weight loss was determined in 7 preterm (gestational age 30-36 weeks) and 6 term infants. TEWL was estimated by measuring the evaporation rate at three sites of the body using the water vapour pressure gradient method. On day 1, TEWL was highest in the most preterm infants, whereas TEWL and urine production were higher in large for gestational age infants as compared to appropriate for gestational age (AGA) infants of the same gestational age (31-36 weeks). For the whole group, weight loss on day 1 was correlated with TEWL (r = 0.49, p < 0.05). At follow-up TEWL in preterm infants remained almost constant during the first 4 days and decreased after the fourth day, at which time weight gain commenced. Preterm AGA infants (gestational age 24-37 weeks) showed a mean postnatal weight loss of 4.4% of the birth weight, while in term infants this loss was only 2.6%. A reduced postnatal weight loss as compared to Caucasian infants may be explained by a lower water loss during the first days after birth, through both skin evaporation and urine excretion.

Water, energy and early postnatal growth in preterm infants

Non-invasive methods, including stable isotope techniques, indirect calorimetry, nutritional balance and skinfold thickness, have given a new insight into early postnatal growth in neonates. Neonates and premature infants in particular, create an unusual opportunity to study the fluid and metabolic adaptation to extrauterine life because their physical environment can be controlled, fluid and energy balance can be measured and the link between metabolism and the energetics of their postnatal growth can be assessed accurately. Thus the postnatal time course of total body water, heat production, energy cost of growth and composition of weight gain have been quantified in a series of "healthy" low-birth-weight premature infants. These results show that total body water is remarkably stable between postnatal days 3-21. Energy expenditure and heat production rates increase postnatally from mean values of 40 kcal/kg/day during the first week to 60 kcal/kg/day in the third week. An apparent energy balance deficit of 180 kcal/kg can be ascribed to premature delivery. The cost of protein metabolism is the highest energy demanding process related to growth. The fact that nitrogen balance becomes positive within 72 h after birth places the newborn in a transitional situation of dissociated balance between energy and protein metabolism during early postnatal growth: skinfold thickness, dry body mass and fat decrease, while there is a gain in protein and increase in supine length. This particular situation ends during the second postnatal week and soon thereafter the rate of weight gain matches statural growth. The goals of the following review are to summarize data on total body water and energy metabolism in premature infants and to discuss how they correlate with physiological aspects of early postnatal growth.

Effect of intrauterine growth retardation on postnatal weight change in preterm infants

To investigate the cause or causes of early postnatal weight change, we measured total body water and fluid and energy balances in 14 preterm infants who were appropriate in size for gestational age (AGA) and in 5 weight-matched, preterm, small-for-gestational-age (SGA) infants. On the first day of life, AGA and SGA infants had the same weight and total body water content. At 6 +/- 2 days (mean +/- SD), AGA infants had had significant weight loss (94 +/- 45 gm) and body water loss (67 +/- 80 ml), whereas weight and total body water content in the SGA infants at the same age (5 +/- 1 days) did not differ from the values at birth. Loss of weight and total body water in AGA infants was accompanied by a greater diuresis than in SGA infants at the same amount of fluid intake. At the end of week 1, AGA and SGA infants had the same total energy expenditure (184 +/- 33 vs 171 +/- 17 kJ.kg-1 x day-1); energy intake, which had exceeded total energy expenditure from the third day of life and beyond, already provided 188 +/- 46 (AGA) or 209 +/- 109 kJ.kg-1 x day-1 (SGA), respectively, for energy storage. Nitrogen balance was positive. Subsequent weight gain occurred at the same rate in AGA and SGA infants; both total body water and solids increased. Energy intake, total energy expenditure, and the amount of energy stored (measured during stable weight gain on a regimen of full enteral feedings) had significantly increased compared with week 1, but both groups maintained similar energy storage.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between nutrition, weight change, and fluid compartments in preterm infants during the first week of life

This study was conducted to investigate the redistribution of fluid compartments and to examine the factors contributing to the variability of early weight loss in premature infants. Fourteen preterm infants (mean +/- SD: birth weight, 1473 +/- 342 gm; gestational age, 30.7 +/- 2.4 weeks) were studied at 1 and 7 days of age. Total body water was measured by deuterium oxide dilution, extracellular volume by bromide dilution, and intracellular volume by the difference between total body water and extracellular volume. There were significant changes in body fluid distribution per concurrent weight from birth to age 1 week. Extracellular volume decreased by 11%, and intracellular volume increased by 8.5% with no change in total body water. Infants were then grouped according to postnatal weight loss (group 1 (n = 7) > 10% and group 2 (n = 7) < 5% of birth weight). In group 1 there was a significant loss of both weight (mean +/- SD: 15.6% +/- 3.7%) and extracellular volume (15.9% +/- 9% of birth weight), with no change in intracellular volume. In group 2 there was no significant weight loss (1.4% +/- 1.8%), but a significant loss of extracellular volume (13.0% +/- 5.4% of birth weight) and a significant increase in intracellular volume. Other differences between the groups were a lower energy intake in group 1 than in group 2 (mean +/- SD: 177 +/- 46 vs 269 +/- 45 kilojoules/kg per day; p < 0.005) and a higher physiologic stability index in group 1 (p < 0.05). We conclude that significant postnatal weight loss as a result of the contraction of the extracellular compartment occurs only in less stable infants whose energy intake is inadequate. With adequate energy intake, weight loss is minimal because of the expansion of the intracellular compartment, which may be related to the onset of growth.

Body composition, nutrition, and fluid balance during the first two weeks of life in preterm neonates weighing less than 1500 grams

To determine whether body weight during the first 2 weeks of life in preterm infants weighing less than 1500 gm reflects nutritional status or fluid balance, we studied total body water (TBW) (deuterium oxide dilution), extracellular volume (sucrose dilution), and plasma volume (Evans blue dilution), together with intake-output studies of nitrogen, fluid, and sodium on day 1 (median age 0.3 day), at a weight loss of 7.8% of birth weight (median age 3.4 days), and after birth weight was regained (median age 8.9 days) in eight clinically stable preterm infants (birth weight 810 to 1310 gm, gestational age 26 to 30 weeks) receiving ventilatory support. During the initial weight loss we found no evidence of catabolism. Body solids (weight--TBW) remained unchanged, there was nitrogen retention, and energy intake was sufficient to meet energy expenditure by day 2. However, we found evidence of fluid loss: TBW (mean +/- SD, -95 +/- 99 ml), extracellular volume (-98 +/- 63 ml), and interstitial volume (-102 +/- 75 ml) decreased significantly, indicating negative fluid and sodium balances. Blood volume and plasma volume remained unchanged. With the regaining of birth weight there was no increase in body solids despite a high degree of nitrogen retention, but there was a positive fluid balance although no significant increase in any body fluid compartment was found. We conclude that the observed postnatal weight changes reflect changes in interstitial volume.

Special needs of the newborn infant in fluid therapy

The preterm baby, although less able to tolerate high fluid and solute loads, has a remarkable ability to adapt to a rather broad range of environmental challenges, and thus renal function in the preterm infant should no longer be considered impaired. Lower rather than higher fluid administration is the current trend in neonatal care because it is safer and more physiologic. Although changes in body weight over time provide a good indicator of water balance, determination of plasma and urine electrolytes and tonicity are also essential in the monitoring of fluid therapy in preterm infants.

Weight loss in full-term negroid infants: relationship to body water compartments at birth?

The possible influence of the body fluid compartments at birth on postnatal weight loss was studied in normal term negroid infants when on a standardized oral fluid, sodium and energy regimen during the first three days of life. Measurements of plasma volume (PV), total body water (TBW), and extracellular water (ECW) were performed simultaneously on vaginally-born infants on the first day of life, by using a triple indicator (Evans blue, deuterium oxide and sucrose) single injection dilution technique. PV was 54 +/- 7 ml/kg (N = 9), TBW was 751 +/- 50 ml/kg (N = 13) and ECW was 311 +/- 61 ml/kg (N = 13) (mean +/- S.D.). Postnatal weight loss (3.7% of birth weight) occurred during the first two days. The postnatal weight loss was not related to any of the body water compartments. However, there was a highly significant correlation with the (cumulative) urine water excretion (r = 0.833, P less than 0.001 on day 1, with similar values for days 1 and 2).

The ontogenesis of skin and organ characteristics in the Syrian golden hamster. I. Skin compartments and subcutaneous adipocytes

The quantitative relations between the 4 skin compartments [epidermis, stratum (str.) papillare, str. reticulare, panniculus carnosus], the hair follicle density and adipocyte size were investigated histometrically in a total of 464 golden hamsters of both sexes of the acromelanic white inbred strain Bio 1.5 and agouti coloured outbred strain Han:AURA. The overall regular course of ontogenesis from the 1st to the 365th day of life showed discontinuous impairments of the skin layer thickness in the shoulder and sacral region due to the spontaneous growth cycles of hair. Active phases of hair growth could be determined on days 15-25, 50-60 and 80-110 from measurements of the hair follicle density as well as skin thickness. In particular, the thickness of the str. reticulare was closely correlated to the growth cycles. By contrast, the epidermis, str. papillare and skin muscle thickness showed an age-dependent development. Also, no correlation was found between the size of inguinal adipocytes and hair growth cycle, which is in contrast to the data from the literature for small laboratory rodents. Only differences in skin muscle thickness could be found in the sites studied in the shoulder and sacral regions. Overall, the skin compartments, the skin follicle density and adipocyte size were found to be stable to effects such as animal strain, sex and skin localization.

Postnatal weight loss in preterm neonates less than 1,500 g is due to isotonic dehydration of the extracellular volume

Weight, extracellular volume (ECV; distribution volume of sucrose) and renal function were studied in 13 preterm infants at birth (age 6 h (2-12); median, range) and again when postnatal weight loss exceeded 5% of birth weight (age 84 (64-97) h). Gestational age was 28 (26-32) weeks, and birthweight was 1,170 g (810-1,455). The infants were nursed in incubators and mechanically ventilated. Fluid therapy allowed a weight loss of up to 10% of birthweight. Body weight decreased significantly from 1,101 +/- 202 g at birth to 1,016 +/- 198 g at day 3 and ECV from 499 +/- 155 ml to 413 +/- 118 ml. Mean weight loss of 85 +/- 50 g was the same as mean ECV loss of 86 +/- 48 ml, suggesting that postnatal weight loss is water loss from the ECV. Weight loss was preceded by a marked increase in diuresis, exceeding fluid intake on day 2. Creatinine clearance did not change. The increased urine output led to a significant increase of sodium excretion without inducing hyponatremia but resulted in an isotonic reduction of ECV.

Growth and total body water in premature infants fed "in-utero" or "ex-utero"

Total body water and anthropometric measurements were compared in two groups of premature infants. The first group included infants with birthweights less than 1,501 g who were fed under usual clinical circumstances and studied at a bodyweight of 1,800-2,100 g ("Ex-utero"); the second group of infants had a birthweight of 1,800 to 2,100 g and were studied within the first week of life ("In-utero"). Triceps and subscapular skinfold thicknesses were significantly greater in "Ex-utero" infants than in "In-utero" infants, whereas body length was significantly greater in the latter group compared to the former. There were no difference in total body water, abdominal skinfold thickness, or midarm circumference between the two groups. These data suggest that feeding premature infants a standard premature infant formula under established guidelines leads to differences in body and fat distribution but not total body water compared to infants nourished "in utero".