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Effect of intrauterine growth retardation on postnatal weight change in preterm infants
K Bauer1, R M Cowett, G M Howard
1Department of Pediatrics, Brown University School of Medicine, Providence, Rhode Island.
Insights
Preterm infants appropriate for gestational age (AGA) lose weight and body water early post-birth due to greater fluid loss, unlike small-for-gestational-age (SGA) infants. Both groups achieve similar weight gain and energy storage later.
Area of Science:
- Neonatal Physiology
- Pediatric Nutrition
- Infant Metabolism
Background:
- Early postnatal weight change is a critical indicator of infant health and development.
- Preterm infants, especially those small for gestational age (SGA), face unique challenges in weight regulation.
- Understanding fluid and energy balance is crucial for optimizing care for preterm infants.
Purpose of the Study:
- To investigate the underlying causes of early postnatal weight changes in preterm infants.
- To compare fluid and energy balance between appropriate-for-gestational-age (AGA) and small-for-gestational-age (SGA) preterm infants.
- To identify factors contributing to weight loss or maintenance in the first week of life.
Main Methods:
- Measurement of total body water, fluid balance, and energy balance in 14 AGA and 5 SGA preterm infants.
- Assessment of infants on the first day of life and at approximately 5-6 days of age.
- Analysis of energy intake, expenditure, and storage, along with nitrogen balance.
Main Results:
- AGA infants experienced significant weight and body water loss by day 6, accompanied by greater diuresis than SGA infants.
- SGA infants maintained their birth weight and total body water content during the first week.
- Both groups exhibited positive nitrogen balance and similar rates of subsequent weight gain, with comparable energy storage by the end of week 1.
Conclusions:
- Early postnatal weight and water loss in AGA preterm infants are primarily driven by increased fluid diuresis.
- SGA preterm infants demonstrate a different fluid management strategy, preserving body weight and water.
- Despite initial differences, both AGA and SGA preterm infants achieve similar growth trajectories and energy storage by the end of the first week.
Abstract:
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)