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Composition of postnatal weight loss & subsequent weight gain in preterm infants
1Department of Paediatrics, Postgraduate Institute of Medical Education & Research, Chandigarh.
Insights
Postnatal weight loss in preterm infants is mainly due to extracellular water loss. Subsequent weight gain involves cellular growth and intracellular water increase, even as extracellular water continues to decrease.
Area of Science:
- Neonatal physiology
- Body composition analysis
- Infant nutrition
Background:
- Preterm infants experience significant postnatal weight loss.
- Understanding body composition changes is crucial for infant health.
- Birth weight regain is a key milestone in neonatal care.
Purpose of the Study:
- To investigate changes in total body water (TBW), extracellular water (ECW), and intracellular water (ICW) during postnatal weight loss and regain in preterm infants.
- To determine the components of weight loss and gain in appropriate for gestational age (AGA) preterm infants.
- To elucidate the relationship between extracellular and intracellular water dynamics during early postnatal development.
Main Methods:
- Measurement of TBW and ECW at birth, peak weight loss, and birth weight regain in 23 preterm AGA infants.
- Calculation of ICW by subtracting ECW from TBW.
- Determination of body solids by subtracting TBW from body weight.
Main Results:
- Postnatal weight loss (6.9% of birth weight) was primarily due to body water loss (7.9% of TBW), with ECW loss accounting for 90% of this water loss.
- During weight regain, 48% of the gain was TBW (predominantly ICW) and 52% was body solids.
- A continuous decrease in TBW and ECW per kg body weight was observed, alongside a gain in ICW and body solids per kg.
Conclusions:
- Postnatal weight loss in preterm infants (31-36 weeks) is mainly a loss of ECW.
- Subsequent weight gain is driven by cellular growth and ICW accumulation.
- ECW loss can persist even when weight gain and solid accumulation have commenced in preterm infants.
Abstract:
To investigate the changes in body composition corresponding to postnatal weight loss and regaining of birth weight, total body water (TBW) and extracellular water (ECW) were measured at birth, on the day of maximum weight loss and on regaining of birth weight in 23 preterm appropriate for gestational age (AGA) infants (mean +/- SD birth weight 1902 +/- 242 g, gestational age 236 +/- 7 days). Intracellular water (ICW) was determined by the difference between TBW and ECW and body solids by the difference between TBW and body weight. Almost 90 per cent of early postnatal weight loss of 132 +/- 38 g (6.9% of birth weight) was because of loss of body water (117 +/- 30 ml; 7.9% of TBW at birth). ECW loss (mean +/- SD 106 +/- 35 ml) accounted for 90 per cent of the TBW loss. Of the subsequent weight gain (134 +/- 40 g) till regaining of birth weight, 48 per cent (64 +/- 28 ml) was TBW and 52 per cent (70 +/- 13 g) body solids. The major gain in body water was in ICW (47 +/- 21 ml). A gradual decrease in TBW and ECW, and a gain in ICW and body solids per kg body weight was observed throughout the study period. These findings favour the concept that in preterm (31-36 wk) infants (i) postnatal weight loss is primarily a reflection of ECW loss and subsequent weight gain is because of cellular growth, (ii) postnatal loss of ECW continues even when weight gain and accumulation of body solids has started.