title: Population-based placental weight ratio distributions.
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.
authors.affiliation: Department 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.
authors.forename: Erin M
authors.initials: EM
authors.lastname: Macdonald
authors.affiliation: Department of Epidemiology and Biostatistics, The University of Western Ontario, London, ON, Canada N6A 5C1.
authors.forename: John J
authors.initials: JJ
authors.lastname: Koval
authors.affiliation: Department of Obstetrics and Gynecology, The University of Western Ontario, London, ON, Canada N6A 5C1 ; Department of Paediatrics, The University of Western Ontario, London, ON, Canada N6A 5C1.
authors.forename: Renato
authors.initials: R
authors.lastname: Natale
authors.affiliation: Department of Obstetrics and Gynecology, The University of Western Ontario, London, ON, Canada N6A 5C1 ; Children Health Research Institute, London, ON, Canada N6C 2V5 ; Department of Physiology and Pharmacology, The University of Western Ontario, London, ON, Canada N6A 5C1.
authors.forename: Timothy
authors.initials: T
authors.lastname: Regnault
authors.affiliation: Department 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 ; Department of Paediatrics, The University of Western Ontario, London, ON, Canada N6A 5C1.
authors.forename: M Karen
authors.initials: MK
authors.lastname: Campbell