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Body water content of extremely preterm infants at birth
G Hartnoll1, P Bétrémieux, N Modi
1University Hospital Lewisham, London SE13 6LH, UK.
Insights
Small for gestational age (SGA) preterm infants have higher body water content than appropriately grown (AGA) preterm infants. This study provides crucial baseline data for understanding growth in preterm infants.
Area of Science:
- Neonatal physiology
- Pediatric growth studies
Background:
- Preterm birth is linked to impaired infant growth.
- Small for gestational age (SGA) status increases risks for preterm infants.
Purpose of the Study:
- To determine body water content in appropriately grown (AGA) and SGA preterm infants.
- Establish a baseline for longitudinal growth studies in preterm infants.
Main Methods:
- Studied infants born between 25 and 30 weeks gestational age.
- Measured extracellular fluid via bromide dilution.
- Measured total body water using H(2)(18)O dilution.
Main Results:
- SGA infants exhibited significantly higher body water content (906 ml/kg) compared to AGA infants (844 ml/kg).
- No significant differences were found in extracellular or intracellular fluid volumes or their ratio.
- Estimated body fat content was approximately 7% in AGA infants, assuming negligible fat in SGA infants.
Conclusions:
- Presents novel body water composition values for SGA preterm infants (25-30 weeks gestation).
- Findings do not support the hypothesis of extracellular dehydration in SGA infants.
- SGA preterm infants do not appear to have impaired body water regulation.
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.