Measures of relative umbilical cord insertion account for 26% of birthweight variance

Abstract

FOR 26% OF BIRTHWEIGHT VARIANCE CAROLYN SALAFIA, JOHN THORP, JR, ELIZABETH MAAS, BARBARA EUCKER, FRANCES SMITH, DAVID SAVITZ, EarlyPath Diagnostic Services, Epidemiology and Pathology, Larchmont, NY University of North Carolina at Chapel Hill, Obstetrics/ Gynecology, Chapel Hill, NC University of North Carolina at Chapel Hill, Chapel Hill, NC OBJECTIVE: Standard placental measures at delivery include the distance in cm from the umbilical cord insertion (UCI) to the closest placental margin. Using digital image analysis, much more detailed information can be collected, and moreover, measurements can be analyzed in relation to other potentially meaningful landmarks. This study explores the associations of standard and novel measures of UCI to birthweight (BWT). STUDY DESIGN: The Pregnancy, Infection and Nutrition (PIN) study is a cohort study of pregnant women recruited at mid-pregnancy from an academic health center in central North Carolina. All PIN subjects plan delivery at the UNC Women’s Hospital. The population was restricted to 287 placentas delivered after 24 completed weeks’ gestation. A digital image of fetal surface is analyzed using Scanalytics software (Fairfax, VA). The placental edge with the shortest distance to the site of membrane rupture is identified and positioned at 6 o’clock. The perimeter of the placenta is traced, and the UCI, marked. A standardmeasure of the distance fromUCI to nearest placental margin is taken, and novel measures of the distance from UCI to the centroid, the weighted center of the placenta area. A stepwise regression enteredfirst the standard, next the novel UCI measure, and last GA, in models predicting BWT. r RESULTS: Standard UCI–nearest placental margin accounted for 8% of BWT variance (r); addition of UCI-centroid captured an additional 18% of BWT r. Addition of GA captured an additional 40% of BWT r, but the UCI measures retained independent effects on BWT. Each cm of increasing distance from the nearest placental margin contributed 115 g (5-95% CI 80-151) increased BWT. Each cm of increasing distance of UCI from the centroid contributed 92 g (5-95% CI 57-128) BWT. CONCLUSION: BWT shows measurable associations with very early pregnancy events; these data may contribute to clarifying timing and mechanisms of BWT associations with long-term health risks.