Wharton's jelly in the umbilical cord. A study of its quantitative variations and clinical correlates

A frozen segment was prepared from each of 398 consecutively collected umbilical cords after stripping them of blood. Three cross-sections were obtained from each cord, and dye imprints were made. Their surface area was measured by placing a transparency with a grid of squares over the imprint and counting the number of squares it occupied. An average of these three cross-sectional areas was taken to estimate the quantity of Wharton's jelly at any point along the umbilical cord. Of the 14 maternal and fetal variables studied, those that were found to be independently related to the estimated quantity of Wharton's jelly in the umbilical cord were male gender (P = < .01), weight of the fetus (P = .05) and maternal prepregnancy weight (P = < .01). These variables, however, explained only 7% of the observed variation in quantity. A further 3.3% was explained by measurement error, leaving 89.7% of the observed variation unexplained.