After completing this article, readers should be able to: 1. Describe theories of the factors that affect umbilical cord length and twisting. 2. Describe the most common umbilical cord abnormality. 3. Delineate structural abnormalities found in the umbilical cord. 4. Describe the effects of meconium on the umbilical cord. The umbilical cord, lifeline of the fetus, is very much undervalued and certainly not being studied sufficiently frequently. The obstetrician and the neonatologist should be familiar with some of its abnormalities, especially when caring for sick neonates. Moreover, some of the observations made at delivery obviously cannot be retrieved in future and may have medicolegal consequences. Therefore, at least the length of the cord should be measured at birth and the number of vessels ascertained. To aid in this task, this article highlights the most important features with which obstetricians, neonatologists, and pathologists should be familiar. The normal human umbilical cord measures approximately 55 cm at term; it grows steadily during gestation (Fig. 1) in concert with the fetal crown-rump length. Figure 1. Growth of umbilical cord compared with the crown-rump length of the fetus. Umbilical cord length varies widely among neonates and in animals, and numerous publications provide measurements for individual species. (1) Often, the length has been correlated with the length of the fetus, but numerous significant exceptions have been noted when attempts were made to identify underlying mechanisms. (2) Despite the many publications that address cord development, it still is not understood fully what regulates length of the umbilical cord. I believe that it is primarily the amount of fetal movement, with much of the excessive lengths of some cords already acquired early in gestation when there still is sufficient space for easy movement. My reasons for this assumption are the following: 1) The cords of fetuses that have severely diminished motions (eg, osteogenesis …