Association of placental weight with cerebral palsy: population-based cohort study in Norway

ObjectiveTo study the risk of cerebral palsy (CP) associated with placental weight, and also with placental weight/birthweight ratio and placental weight/birth length ratio. DesignPopulation-based cohort study. SettingPerinatal data in the Medical Birth Registry of Norway were linked with clinical data in the CP Register of Norway. PopulationA total of 533 743 singleton liveborn children in Norway during 1999-2008. Of these, 779 children were diagnosed with CP. MethodsPlacental weight, placental weight/birthweight ratio, and placental weight/birth length ratio were grouped into gestational age-specific quartiles. Odds ratios (OR) with 95% confidence intervals (95% CI) for CP were calculated for children with exposure variables in the lowest or in the highest quartile, using the second to third quartile as the reference. Main outcome measuresCP and CP subtypes. ResultsOverall, children with low placental weight had increased risk for CP (OR 1.5, 95% CI 1.2-1.7). Low placental weight/birthweight ratio (OR 1.2, 95% CI 1.0-1.4) and low placental weight/birth length ratio (OR 1.5, 95% CI 1.2-1.8) were also associated with increased risk for CP. In children born at term, low placental weight was associated with a twofold increase in risk for spastic bilateral CP (including both quadriplegia and diplegia) (OR 2.1, 95% CI 1.5-2.9). In children born preterm, high placental ratios were associated with increased risk for spastic quadriplegia. ConclusionsOur results suggest that placental dysfunction may be involved in causal pathways leading to the more severe subtypes of CP. Tweetable abstractLow placental weight increases the risk for cerebral palsy, especially for the spastic bilateral subtype. Tweetable abstract Low placental weight increases the risk for cerebral palsy, especially for the spastic bilateral subtype.