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Published on: November 8, 2018
Population-based placental weight ratio distributions
Erin M Macdonald1, John J Koval2, Renato Natale3
1Department of Epidemiology and Biostatistics, The University of Western Ontario, London, ON, Canada N6A 5C1 ; Department of Obstetrics and Gynecology, The University of Western Ontario, London, ON, Canada N6A 5C1 ; Children Health Research Institute, London, ON, Canada N6C 2V5.
Insights
The placental weight ratio (PWR) indicates fetal and placental growth balance. This study established PWR standards by gestational age and found it differs significantly for small (SGA) and large (LGA) for gestational age infants.
Area of Science:
- Obstetrics and Gynecology
- Perinatology
- Fetal Development
Background:
- The placental weight ratio (PWR) is a key indicator of fetal and placental growth balance.
- Established ranges for PWR across gestation and by fetal growth adequacy are currently lacking.
- Understanding PWR variations is crucial for assessing fetal well-being.
Purpose of the Study:
- To establish population-based reference ranges for the placental weight ratio (PWR) stratified by gestational age.
- To investigate the association between PWR distributions and fetal growth adequacy (SGA, AGA, LGA).
Main Methods:
- Retrospective cohort study of 41,441 live singleton births from two hospitals in London, Ontario (over 10 years).
- Inclusion criteria: gestational age 22-42 weeks.
- Nonparametric quantile regression was utilized to model PWR distributions.
Main Results:
- PWR and its dispersion decrease with increasing gestational age.
- Infants small for gestational age (SGA) exhibited a higher proportion of extreme PWRs compared to average (AGA) and large (LGA) for gestational age infants, particularly at earlier gestations.
- On average, SGA infants demonstrated higher PWRs than AGA and LGA infants.
Conclusions:
- The study provides the first population-based reference curves for PWR stratified by fetal growth adequacy.
- These findings highlight significant differences in PWR between SGA, AGA, and LGA infants.
- The established curves serve as valuable population standards for research and clinical applications in fetal growth assessment.
Abstract:
The placental weight ratio (PWR) is a health indicator that reflects the balance between fetal and placental growth. The PWR is defined as the placental weight divided by the birth weight, and it changes across gestation. Its ranges are not well established. We aimed to establish PWR distributions by gestational age and to investigate whether the PWR distributions vary by fetal growth adequacy, small, average, and large for gestational age (SGA, AGA, and LGA). The data came from a hospital based retrospective cohort, using all births at two London, Ontario hospitals in the past 10 years. All women who delivered a live singleton infant between 22 and 42 weeks of gestation were included (n = 41441). Nonparametric quantile regression was used to fit the curves. The results demonstrate decreasing PWR and dispersion, with increasing gestational age. A higher proportion of SGA infants have extreme PWRs than AGA and LGA, especially at lower gestational ages. On average, SGA infants had higher PWRs than AGA and LGA infants. The overall curves offer population standards for use in research studies. The curves stratified by fetal growth adequacy are the first of their kind, and they demonstrate that PWR differs for SGA and LGA infants.
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