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Birth weight and longitudinal growth in infants born below 32 weeks' gestation: a UK population study
Tim J Cole1, Yevgeniy Statnikov, Shalini Santhakumaran
1MRC Centre of Epidemiology for Child Health, UCL Institute of Child Health, , London, UK.
Insights
This study reveals that very preterm infants often experience postnatal weight loss, particularly those born later. Establishing a target weight centile at birth may be detrimental for these vulnerable babies.
Area of Science:
- Neonatalogy
- Pediatric Growth and Development
- Clinical Data Analysis
Background:
- Accurate assessment of birth weight and postnatal weight gain is crucial for monitoring the health of very preterm infants.
- Routinely captured electronic clinical data offers a valuable resource for studying growth patterns in neonatal populations.
Purpose of the Study:
- To characterize birth weight and postnatal weight gain trajectories in infants born before 32 weeks' gestation.
- To utilize electronic health records for a contemporary analysis of neonatal growth.
- To inform clinical practice regarding weight management in extremely preterm infants.
Main Methods:
- Analysis of anonymized longitudinal weight data from 5009 infants born between 22-31 weeks' gestation (2006-2011).
- Construction of birth weight centiles using the LMS method.
- Summarization of longitudinal weight gain using Superimposition by Translation and Rotation (SITAR) growth curve analysis.
Main Results:
- Girls weighed significantly less than boys at birth (6.6% less).
- Infants born at 31 weeks' gestation experienced an average weight loss of 258g, reaching a nadir around day 8, followed by increased weight gain.
- Infants born before 29 weeks' gestation generally did not experience postnatal weight loss, while those born later showed marked weight loss. Babies tended to cross weight centiles downwards for at least two weeks.
Conclusions:
- Very preterm infants commonly show a downward trend in weight centiles post-birth.
- Postnatal weight loss patterns differ significantly based on gestational age at birth, being minimal before 29 weeks and more pronounced thereafter.
- Setting an infant's target centile at birth is potentially harmful; it is advisable to establish this once weight gain has stabilized, reflecting current medical management practices.
Objective:
To describe birth weight and postnatal weight gain in a contemporaneous population of babies born <32 weeks' gestation, using routinely captured electronic clinical data.
Design:
Anonymised longitudinal weight data from 2006 to 2011.
Setting:
National Health Service neonatal units in England.
Methods:
Birth weight centiles were constructed using the LMS method, and longitudinal weight gain was summarised as mean growth curves for each week of gestation until discharge, using SITAR (Superimposition by Translation and Rotation) growth curve analysis.
Results:
Data on 103 194 weights of 5009 babies born from 22-31 weeks' gestation were received from 40 neonatal units. At birth, girls weighed 6.6% (SE 0.4%) less than boys (p<0.0001). For babies born at 31 weeks' gestation, weight fell after birth by an average of 258 g, with the nadir on the 8th postnatal day. The rate of weight gain then increased to a maximum of 28.4 g/d or 16.0 g/kg/d after 3 weeks. Conversely for babies of 22 to 28 weeks' gestation, there was on average no weight loss after birth. At all gestations, babies tended to cross weight centiles downwards for at least 2 weeks.
Conclusions:
In very preterm infants, mean weight crosses centiles downwards by at least two centile channel widths. Postnatal weight loss is generally absent in those born before 29 weeks, but marked in those born later. Assigning an infant's target centile at birth is potentially harmful as it requires rapid weight gain and should only be done once weight gain has stabilised. The use of electronic data reflects contemporary medical management.
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