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Weight of preterm newborns during the first twelve weeks of life
L M Anchieta1, C C Xavier, E A Colosimo
1Maternidade Odete Valadares, Fundação Hospitalar do Estado de Minas Gerais and Hospital Universitário, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil. lenima@terra.com.br
Insights
Preterm infants appropriate-for-gestational-age experienced initial weight loss, then regained birth weight within 3 weeks. Relative weight gain velocity peaked at 3 weeks, becoming similar across birth weight groups by 12 weeks.
Area of Science:
- Neonatology
- Pediatric Growth and Development
- Infant Nutrition
Background:
- Premature infants appropriate-for-gestational-age (AGA) require careful monitoring of postnatal growth.
- Understanding weight gain patterns is crucial for optimizing nutritional support and clinical outcomes in preterm neonates.
Purpose of the Study:
- To assess the weight changes and somatic growth velocity of preterm AGA infants during the first twelve weeks of life.
- To analyze the relationship between birth weight and weight gain rates in this population.
Main Methods:
- A longitudinal study of 260 preterm AGA infants (birth weight <2500 g) in Belo Horizonte, Brazil (1996).
- Weekly weight evaluations, with infants grouped by birth weight at 250-g intervals.
- Somatic growth curves constructed using Count's model to derive absolute (g/day) and relative (g kg-1 day-1) velocity curves.
Main Results:
- Infants exhibited initial weight loss (5.9–13.3%) in the first week, with greater loss in lower birth weight groups.
- Birth weight was recovered between 17 and 21 days post-birth.
- Absolute weight gain (g/day) was proportional to birth weight, while relative weight gain (g kg-1 day-1) was inversely proportional, peaking at week 3.
- By week 12, relative weight gain velocity normalized across all birth weight groups.
Conclusions:
- Relative velocity is a robust indicator of weight gain in preterm AGA infants.
- Weight gain patterns vary with birth weight, particularly in the early weeks post-preterm birth.
- Nutritional strategies may need to account for these differential growth rates to ensure optimal development.
Abstract:
A longitudinal and prospective study was carried out at two state-operated maternity hospitals in Belo Horizonte during 1996 in order to assess the weight of preterm appropriate-for-gestational-age newborns during the first twelve weeks of life. Two hundred and sixty appropriate-for-gestational-age preterm infants with birth weight <2500 g were evaluated weekly. The infants were divided into groups based on birth weight at 250-g intervals. Using weight means, somatic growth curves were constructed and adjusted to Count's model. Absolute (g/day) and relative (g kg-1 day-1) velocity curves were obtained from a derivative of this model. The growth curve was characterized by weight loss during the 1st week (4-6 days) ranging from 5.9 to 13.3% (the greater the percentage, the lower the birth weight), recovery of birth weight within 17 and 21 days, and increasingly higher rates of weight gain after the 3rd week. These rates were proportional to birth weight when expressed as g/day (the lowest and the highest birth weight neonates gained 15.9 and 30.1 g/day, respectively). However, if expressed as g kg-1 day-1, the rates were inversely proportional to birth weight (during the 3rd week, the lowest and the highest weight newborns gained 18.0 and 11.5 g kg-1 day-1, respectively). During the 12th week the rates were similar for all groups (7.5 to 10.2 g kg-1 day-1). The relative velocity accurately reflects weight gain of preterm infants who are appropriate for gestational age and, in the present study, it was inversely proportional to birth weight, with a peak during the 3rd week of life, and a homogeneous behavior during the 12th week for all weight groups.
