Clinical profile of early postnatal body weight changes in extremely low birth weight infants

Abstract

Background: Early postnatal weight changes are widely variable and unpredictable in the extremely low birth weight infants (ELBW, birth weight < 1000 g). As the fluid volume therapy is calculated based on the body weight these changes could potentially have implications in the hydration related morbidities in them. Early postnatal weight changes have not been systematically investigated in this population.

Objectives: To determine the pattern and magnitude of weight changes early in life and its relationship with maturation and birth weight (BW) in ELBW infants.

Methods: We studied the maximum weight loss (MWL), and the daily body weight changes from birth weight (DΔ bw) during the first 15 days of life. Prospectively entered infants' and maternal demographic and relevant clinical data were retrospectively extracted via computerized reports and chart reviews during a three-year study period. MWL and DΔ bw (calculated as % of birth weight and expressed as mean ± SD) were determined and correlated with gestational age (GA) and BW. Data were analyzed via Pearson's correlation co-efficient and the ordinary least square regression tests.

Results: The mean ± standard deviation of GA and BW in 102 enrolled ELBW infants were 26.1 ± 2 weeks and 779.9 ± 157 g respectively. MWL in the entire cohort was 14.2 ± 5.4%. After initial loss the BW was regained on 14.5 ± 4.2 postnatal days of life. MWL varied widely within unit GA groups and was highest in infants born at 23 weeks. MWL correlated inversely with GA (r= − 0.3, p=0.007) but not with BW (r=0.17, p=0.09). DΔ bw varied widely and was highest on postnatal day 4. DΔ bw correlated negatively and significantly with GA during days 1–8 of life (p 0.05 to < 0.01) except for day 2 (p= 0.06). The slopes of regression coefficients for the two variables were also negative and highly significant during postnatal days 1–8 (p < 0.01) except for day 2 (p= 0.06). DΔ bw did not correlate with GA during 9–15 postnatal days and displayed a positive slope on day 15.

Conclusions: MWL is related inversely to GA and has no relationship with BW in ELBW infant. DΔ bw is predictable by GA during the first but not the second postnatal week. The BW is regained on an average of 14 days of postnatal life.