Projects per year
Abstract
Introduction
The ratio of birthweight to placental weight (BW:PW) is often used as a measure of placental efficiency in humans and animals. However, ratios have properties that are known to lead to spurious results. An alternative approach is the use of residuals from regression, which reflect whether birthweight is higher or lower than expected for a given placental weight, given the population pattern. We hypothesized that biologically meaningful measures of placental efficiency would differ between placentas with and without pathology, and between adverse and normal perinatal and postnatal outcomes.
Methods
We examined associations between measures of placental efficiency (BW:PW ratio or residuals) and placental pathology, Apgar scores and infant death using National Collaborative Perinatal Project data (4645 preterm births and 28497 term births).
Results
BW:PW ratios and residuals were significantly lower in placentas showing pathologies including signs of large infarcts or hemorrhage, although many of these differences were small. Low BW:PW ratios and residuals were also associated with low Apgar scores and increased risk of postnatal death. Whereas residuals were lower in term placentas that appeared immature by microscopic examination, the opposite was true for BW:PW ratios.
Conclusion
The BW:PW ratio produced an artefact whereby histologically less mature placentas at term appeared to be more “efficient” than mature placentas, illustrating a known problem with the use of ratios. For other traits, residuals generally showed differences between placentas with and without pathology that were as great as those seen with BW:PW ratios, and often showed stronger associations with adverse outcomes.
The ratio of birthweight to placental weight (BW:PW) is often used as a measure of placental efficiency in humans and animals. However, ratios have properties that are known to lead to spurious results. An alternative approach is the use of residuals from regression, which reflect whether birthweight is higher or lower than expected for a given placental weight, given the population pattern. We hypothesized that biologically meaningful measures of placental efficiency would differ between placentas with and without pathology, and between adverse and normal perinatal and postnatal outcomes.
Methods
We examined associations between measures of placental efficiency (BW:PW ratio or residuals) and placental pathology, Apgar scores and infant death using National Collaborative Perinatal Project data (4645 preterm births and 28497 term births).
Results
BW:PW ratios and residuals were significantly lower in placentas showing pathologies including signs of large infarcts or hemorrhage, although many of these differences were small. Low BW:PW ratios and residuals were also associated with low Apgar scores and increased risk of postnatal death. Whereas residuals were lower in term placentas that appeared immature by microscopic examination, the opposite was true for BW:PW ratios.
Conclusion
The BW:PW ratio produced an artefact whereby histologically less mature placentas at term appeared to be more “efficient” than mature placentas, illustrating a known problem with the use of ratios. For other traits, residuals generally showed differences between placentas with and without pathology that were as great as those seen with BW:PW ratios, and often showed stronger associations with adverse outcomes.
Original language  English 

Pages (fromto)  5258 
Number of pages  7 
Journal  Placenta 
Volume  68 
Early online date  3 Jul 2018 
DOIs  
Publication status  Published  1 Aug 2018 
Keywords
 Placenta
 Birthweight
 Efficiency
 Pathology
 Outcome
Fingerprint
Dive into the research topics of 'The problem with using the birthweight:placental weight ratio as a measure of placental efficiency'. Together they form a unique fingerprint.Projects
 1 Finished

Foetal Growth Restriction: A Failure of Placental Adaptation in Response to Foetal Nutrient Demand.
1/09/13 → 31/08/18
Project: Research