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Published on: June 29, 2013
Conventional birth weight standards obscure fetal growth restriction in preterm infants
1School of Reproductive and Developmental Medicine, University of Liverpool, Neonatal Unit, Liverpool Women's Hospital, Liverpool L8 7SS, UK. mc19@liv.ac.uk
Insights
Estimated fetal weight (EFW) better identifies fetal growth restriction (FGR) in preterm infants than birth weight. This improved identification of FGR is crucial for understanding neonatal disease risks and outcomes.
Area of Science:
- Neonatalogy
- Perinatology
- Pediatric Research
Background:
- Fetal growth restriction (FGR) association with fetal maturation is debated, with conflicting evidence on its impact on preterm infant mortality and morbidity.
- Severe FGR can be detrimental, while excessive fetal growth is also linked to adverse outcomes.
- Standard birth weight centiles can obscure FGR in preterm infants due to distorted growth patterns.
Purpose of the Study:
- To investigate if estimated fetal weight (EFW) can reveal the effects of 'hidden' FGR in preterm infants.
- To compare the utility of EFW z-scores versus birth weight z-scores in assessing FGR and its neonatal implications.
Main Methods:
- Analysis of a 25-year database of preterm infants (<35 weeks gestation) admitted to a single neonatal unit.
- Computation of odds ratios (ORs) for mortality and neonatal morbidities based on z-scores for birth weight and EFW.
- Comparison of ORs derived from birth weight z-scores with those derived from EFW z-scores.
Main Results:
- Mortality OR was lowest for birth weights 1-3 SD above the mean, but for EFW, it was lowest between -2 SD and 0 SD below the mean.
- Increasing FGR below the mean reduced the OR for periventricular hemorrhage with both birth weight and EFW.
- Apparent protective effects of higher birth weights (>1 SD above mean) against certain morbidities (e.g., sepsis, CLD, PDA, NEC) were not observed with EFW; severe FGR (>-3 SD) increased NEC risk.
Conclusions:
- Estimated fetal weight (EFW) provides a more accurate assessment of FGR incidence and its role in neonatal diseases compared to standard birth weight standards.
- Utilizing EFW standards is essential for a clearer understanding of FGR's impact on neonatal outcomes.
Background And Objective:
It has been suggested that fetal growth restriction (FGR) is associated with fetal maturation so that, compared with appropriately grown preterm infants, mortality and some neonatal morbidities may be reduced. The evidence for this is conflicting, and severe FGR has been shown to be harmful. In addition excessive growth has also been shown to be associated with poorer outcomes. As preterm infants are often also growth restricted, centiles for birth weights are distorted and may conceal the degree of growth restriction in a given infant. This study investigated whether using estimated fetal weights (EFW) might reveal the effects of hidden FGR.
Population And Methods:
Using a 25-year database of preterm admissions to a single neonatal unit the ORs for mortality and neonatal morbidities for z scores for birth weight above and below the mean were computed and compared with those computed for z scores for EFW.
Results:
In 7898 infants born at less than 35 weeks' gestation, the OR for mortality was lowest for birth weights between 1 SD and 3 SD above the mean, but was lowest for EFW between -2 SD and 0 SD below the mean. For periventricular haemorrhage, increasing FGR below the mean reduced the OR with both birth weight and EFW. Apparent reductions in OR for septicaemia, chronic lung disease, persistent ductus arteriosus and necrotising enterocolitis with birth weights of >1 SD above the mean were not seen with EFW. FGR of >-3 SD was associated with increased OR for necrotising enterocolitis with both birth weight and EFW.
Conclusion:
Using fetal growth rather than birth weight standards gives a better indication of the incidence and role of FGR in neonatal disease.
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