Obstetric conditions and the placental weight ratio

Introduction: To elucidate how obstetric conditions are associated with atypical placental weight ratios (PWR)s in infants born: (a) >= 37 weeks gestation; (b) at >= 33 but <37 weeks gestation; and (c) <33 weeks gestation. Methods: The study included all in-hospital singleton births in London, Ontario between June 1, 2006 and March 31, 2011. PWR was assessed as <10th or >90th percentile by gestational age-specific local population standards. Multivariable analysis was carried out using multinomial logistic regression with blockwise variable entry in order of temporality. Results: Baseline factors and maternal obstetric conditions associated with PWR <10th percentile were: increasing maternal height, overweight and obese body mass indexes (BMI), large for gestational age infants, smoking, and gestational diabetes. Obstetric factors associated with PWR >90th percentile were: underweight, overweight and obese BMIs, smoking, preeclampsia, placenta previa, and placental abruption. In particular, indicators of hypoxia and altered placental function were generally associated with elevated PWR at all gestations. Discussion: An association between obstetric conditions associated with fetal hypoxia and PWR >90th percentile was illustrated. Conclusions: The multivariable findings suggest that the PWR is similarly increased regardless of the etiology of the hypoxia. (C) 2014 Elsevier Ltd. All rights reserved.