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Postnatal

Weight

Changes

in Low Birth Weight

Infants

Stanley

G. Shaffer,

MD, Cheryl

L. Quimiro,

John V. Anderson,

MD, and

Robert

T. Hall,

MD

From the Children’s Mercy Hospital, University of Missouri Kansas City School of

Medicine, Kansas City

ABSTRACT.

Postnatal body weight changes were

as-sessed in 385 surviving infants with birth weights of less than 2,500 g. Body weight was measured daily between birth and 45 days of age. Infants were grouped according to 100-g birth weight categories, and mean body weight changes for each group were compared. Initial postnatal weight loss occurred in each group and ranged between 7.9% and 14.6% of birth weight. Mean postnatal weight loss was greater in the lowest birth weight groups, but considerable variability was observed among individual infants. Duration of postnatal weight loss was similar among all birth weight groups. Weight gain usually began between four and six days of age, and the rate of weight gain expressed as grams per kilogram per day was similar in all birth weight groups. Pediatrics 1987;79:702-705;

low birth weight infant, growth.

Evaluation of daily body weight changes may be a significant adjunct to the care of the low birth weight infant. Changes primarily reflect those of body water composition in the first week or two of life but subsequently may also reflect changes in gnowth and nutnition.’4

The primary reference data describing weight changes during the first 50 days of life in the low birth weight infant were published by Dancis et al5 in 1948. These data were based on the serial body weights of 100 infants weighing less than 2,500 g. Few infants were included who had a birth weight

less than 1,000 g. Subsequently, Brosius et al6 added

data on 14 infants with birth weights between 620 and 900 g and 12 infants weighing between 930 and 1,100 g.

Significant changes have taken place in the

pop-Received for publication Feb 26, 1986; accepted June 10, 1986. Reprint requests to (5.5.) Children’s Mercy Hospital, 24th & Gillham, Kansas City, MO 64108.

PEDIATRICS (ISSN 0031 4005). Copyright © 1987 by the American Academy of Pediatrics.

ulation and cane of low birth weight infants in the nursery today. We have, therefore, assessed the growth patterns of 385 surviving infants with birth weight less than 2,500 g, including 24 infants with birth weights less than 750 g.

Methods

The study population consisted of surviving low birth weight infants admitted to the intensive care nurseries at The Children’s Mercy Hospital and St Luke’s Hospital Peninatal Centen during 1984 and 1985. Seventy-one inborn and 314 outbonn infants were included; 83% were white infants and 15% were black infants. Because we were interested in a cross-sectional survey of our nursery population, infants were included regardless of peninatal prob-lems, nutritional status, or clinical course. No at-tempt was made to exclude infants on any basis other than survival and the availability of complete weight records.

Fluid/electrolyte and nutritional management varied with the infants’ conditions and the expec-tations of the attending physicians. Routine cane included the provision of a neutral thermal envi-nonment within an incubator and administration of panenteral fluids and nutrition until enteral feed-ings were tolerated. Guidelines for fluid therapy included expected weight loss during the first week of life and subsequent weight gain proportional to caloric intake.

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S 10 15 20 25 30 35 40 45 50 66

ARTICLES 703

infants secondary to transfer or discharge exceeded postnatal weight loss was calculated for each 100-g 20% of the original group. Maximum weight loss weight group.

and mean growth rate subsequent to maximum

RESULTS

2300 Mean daily weights of each 100-g birth weight

2200 group are presented graphically in Fig 1. The weight

2100 change pattern of each group is shown in Table 1.

Longitudinal data are limited in larger infants

be-2000 cause of their earlier discharge or transfer from the

1900 nursery.

1800 Initial postnatal weight loss occurred in each

group and ranged between 7.9% and 14.6% of birth

1700 weight. The percentage of weight lost tended to be

.; 1600 greaten in lower birth weight groups, but

consider-) 1600 able variability existed among individual infants

(r = .40, Fig 2). Maximal weight loss usually

oc-.‘ 1400 curred between four and six days. Age at maximal

1300 weight loss was not related to birth weight (Fig 3).

1200 Subsequent weight gain expressed as grams per

1100 day was inversely proportional to birth weight.

However, weight gain expressed as grams pen

kilo-1000 gram of body weight pen day was similar in all

900 infants (Table 1).

800

700

1001 .. : #{149} #{149} #{149}

600 901

801 ..,.- ..!.,..‘ ... .

S0O #{163} . / . . . .

70 #{149}

60 60

50 , ‘ ‘ , ,

0.

0 300 800 800 1200 1800 1800 2100 2400 2700 3000

Postnatal Age (days)

Fig 1. Postnatal weight change observed in 385 low Birthw.iht (ems)

birth weight infants. Mean daily weights of 100-g birth Fig 2. Percentage birth weight at maximal postnatal

weight groups are displayed. weight loss v birth weight.

TABLE 1. Weight Change Patterns of Birth Weight Groups

Birth Wt No. of Mean Lowest Lowest Age at Growth Growth

Group (g) Patients Birth Wt Mean % of Lowest Rate Rate (g/

(g) Wt (g) Birth Wt Wt (d) (g/d) kg/d)

501-600 4 542 472 87.0 5 8.7 18.4

601-700 10 647 566 87.5 5 8.0 14.1

701-800 20 746 637 85.4 5 9.3 14.6

801-900 20 851 732 86.0 6 9.5 13.0

901-1,000 18 952 851 89.4 4 13.7 16.1

1,001-1,100 26 1,050 921 87.7 5 14.4 15.6

1,101-1,200 28 1,150 1,000 87.0 7 17.0 17.0

1,201-1,300 27 1,233 1,095 88.8 3 18.0 15.9

1,301-1,400 19 1,348 1,193 88.5 6 20.7 17.4

1,401-1,500 30 1,445 1,271 88.0 6 18.1 14.2

1,501-1,600 11 1,536 1,308 85.1 6 19.6 15.0

1,601-1,700 18 1,636 1,489 91.0 6 20.7 13.9

1,701-1,800 23 1,744 1,590 91.2 5 18.4 11.6

1,801-1,900 24 1,855 1,709 92.1 5 20.0 11.7

1,901-2,000 17 1,936 1,764 91.1 7 25.7 14.7

2,001-2,100 19 2,044 1,875 91.7 6 24.0 12.8

2,101-2,200 19 2,135 1,945 91.1 6

2,201-2,300 15 2,249 2,038 90.6 7

2,301-2,400 8 2,344 2,105 89.8 5

2,401-2,500 9 2,435 2,252 92.5 8

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0 0

0

12

0 300 600 *00 1200 1600 1600 2100 2400 2700 3000

Birthweight (gms)

Fig 3. Age at lowest postnatal weight v birth weight.

DISCUSSION

Two types of growth charts are presently avail-able for monitoring weight changes in low birth weight infants-those based on postconceptual age and those based on weight at birth. Postconceptual age-adjusted growth curves, such as those compiled by Babson,7 are useful for assessment of long-term nutritional progress in the preterm infant.8

The present study examined birth weight-ad-justed growth patterns. Growth charts adjusted for

birth weight are useful for assessment of short-term weight changes, which probably relate more closely to water balance than nutritional status.

In 1948, Dancis et al5 published postnatal growth curves based upon serial weight changes in 100 low birth weight infants. Selection criteria for the sub-jects were, by intention, broad. Infants were pre-mature, generally free of complications, and orally fed. The results were not intended to provide sta-tistically normative data but simply to represent the growth pattern of premature infants managed in “a certain arbitrary manner.” Many investigators have subsequently provided more specific data ne-garding postnatal growth determinants and expec-tations, but the grid of Dancis et al continues to be a useful clinical tool to illustrate and compare pat-terns of postnatal weight change. We believed that it was appropriate to reexamine the patterns of weight change that occur in the nursery today as evidence accumulates that postnatal water balance significantly affects neonatal monbidity.9’3

It is evident from both the present data and the data reported by Dancis et al5 that appreciable weight reduction occurs in the early postnatal pe-nod. We have found, however, that the extent and pattern ofpostnatal weight reduction in the nursery today are substantially different from those previ-ously described. Dancis et al found that initial weight loss was inversely pnoportional to birth weight (Hammett’s rule) and that the duration of weight loss and the period of time to return to birth weight were more extended in lower birth weight infants.

In the present study, mean weight loss was greaten in each birth weight group than the weight loss reported by Dancis et a! (Table 2). They re-ported postnatal weight losses that increased from 4.8% in the 2,500-g group to 8.0% in the 1,000-g birth weight group. In the present study, mean postnatal weight loss ranged from 7.3% to 14.5%. A trend toward an increased percentage of postna-tal weight loss among lower birth weight categories was observed, but considerable individual vaniabil-ity was noted (Fig 2). The nadir of weight loss occurred between the fourth and sixth days follow-ing birth and was not related to birth weight (Fig. 3).

The appropriateness of differing degrees of initial weight loss cannot be inferred from these data. Early weight loss may represent normalization of relatively expanded fetal water compartment vol-umes.”3’7 In this context, proportionally greaten weight loss is an expected event for infants of lower birth weight. On the other hand, variations in the extent of postnatal weight loss among low birth weight infants may simply reflect prevailing feeding practices and approaches to fluid therapy. In this broad survey of postnatal weight changes, it was not possible to assess the multiple confounding variables contributing to postnatal weight changes (i.e., fetal nutrition and hydration, water and elec-tnolyte balance, caloric intake, and metabolic de-mands). Additional serial data describing changes in body composition and the contribution of these variables would be helpful.

The extent to which fluid therapy and hydration contribute to neonatal morbidity remains unclear. Some evidence suggests that early positive water balance significantly affects neonatal morbidity, including the incidence of patent ductus arteriosus, bronchopulmonary dysplasia, and necrotizing en-terocolitis.9’3 Lorenz et al’8 could not, however, demonstrate a correlation between postnatal weight change and neonatal outcome. Further investiga-tion is necessary to define optimal hydration of the newborn and commensurate postnatal weight changes. The present data do illustrate, however,

TABLE 2. Maximal Post natal Weight Loss

Birth Wt (g) Dancis et al5 Brosius et alt Present Study

G

%

G

%

G

%

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REFERENCES

ARTICLES 705

E

S

20 26 30 36 40

Postnatal Age (days)

Fig 4. Revised postnatal growth grid, including growth curves for 100-g birth weight groups.

that prolonged weight loss in the low birth weight infant is not usual and should not be considered a normal event.

Weight gain subsequent to postnatal weight loss varied between 8.0 and 25.7 g/d. We concur with the observations of Dancis et al5 and, subsequently, Brosius et a!6 that the absolute rate of subsequent weight gain is proportional to birth weight. The present data indicate, however, that growth rates are similar when corrected for body weight. Growth of the low birth weight infant results in an average weight gain of 1% to 2%/d in our population of sick infants. The patterns of weight gain reported here bear no relation to optimal growth rates because the population includes infants with all degrees of nutritional compromise. Hence, although the re-vised birth weight-adjusted growth chart for the low birth weight infant developed here may be useful to identify infants whose weight changes vary from those usually seen in sick infants of compa-rable birth weight, the use of posteonceptual age-adjusted growth curves, such as those compiled by Babson,7 remain preferable for determination of long-term nutritional progress.

1. Shaffer SG, Bradt 5K, Hall RT: Postnatal changes in total body water and extracellular volume in the preterm infant with respiratory distress syndrome. J Pediatr,

1986;109:509-514

2. Osler M, Pedersen J: The body composition of newborn infants of diabetic mothers. Pediatrics 1960;26:985-992 3. Van der Wagen A, Okken A, Westerveen J, et al: Changes

in total body water and extracellular water in small-for-dates newborn infants in the first days of life, abstracted.

Pediatr Res 1983;17:340A

4. Kagan BM, Stanincova V, Felix NS, et al: Body composition of premature infants: Relation to nutrition. Am J Clin Nutr

1972;25:1153-1164

5. Dancis J, O’Connell JR, Holt LE: A grid for recording the weight of preterm infants. J Pediatr 1948;33:570-572

6. Brosius KK, Ritter DA, Kenny JD: Postnatal growth curve of the infant with extremely low birth weight who was fed enterally. Pediatrics 1984;74:778-782

7.

Babson SG: Growth of low birthweight infants. J Pediatr

1970;77:11-18

8. Maisels MJ, Marks KH: Growth chart for sick premature infants. J Pediatr 1981;98:663-664

9. Stevenson JG: Fluid administration in the association of patent ductus arteriosus complicating respiratory distrese syndrome. J Pediatr 1977;90:257-261

10. Brown ER, Stark A, Sosenko I, et al: Bronchopulmonary dysplasia: Possible relationship to pulmonary edema. J Pe-diatr 1978;92:982-984

11. Bell EF, Warburton D, Stonestreet BS, et al: Effect of fluid administration on the development of symptomatic patent ductus arteriosus and congestive heart failure in premature infants. N EngI J Med 1980;302:598-603

12. Bell EF, Warburton D, Stonestreet BS, et al: High-volume fluid intake predisposes premature infants to necrotizing enterocolitis. Lancet 1979;2:90

13. Green TP, Thompson TR, Johnson DE, et al: Diuresis and pulmonary function in premature infants with respiratory distress syndrome. J Pediatr 1983;103:618-623

14. Cook P: A clinical study of the premature infant. Arch

Pediatr 1921;38:201-216

15. Friis-Hansen B: Body water compartments in children: Changes during growth and related changes in body com-position. Pediatrics 1961;28:169-181

16. Cassady G, Milstead RR: Antipyrine space studies and cell water estimates in infants of low birth weight. Pediatr Res

1971;5:673-682

17. Cassady G: Bromide space studies in infants of low birth weight. Pediatr Res 1970;4:14-24

18. Lorenz JM, Kleinman LI, Kotagal VR, et al: Water balance in very low birth weight infants: relationship to water and sodium intake and effect on outcome. J Pediatr 1982; 101:423-432

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1987;79;702

Pediatrics

Stanley G. Shaffer, Cheryl L. Quimiro, John V. Anderson and Robert T. Hall

Postnatal Weight Changes in Low Birth Weight Infants

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1987;79;702

Pediatrics

Stanley G. Shaffer, Cheryl L. Quimiro, John V. Anderson and Robert T. Hall

Postnatal Weight Changes in Low Birth Weight Infants

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Figure

Fig 3.Age at lowestpostnatalweightv birthweight.
Fig 4.Revisedcurvespostnatalgrowthgrid,includinggrowthfor100-gbirthweightgroups.

References

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