Most umbilical cords finally grow to be about the same length as the baby (although there are exceptions), reaching a final length of 20-23.5 in (50-60 cm). The umbilical cord has up to 40 turns along its length and these turns are seven times more likely to twist to the left than the right. The coiling pattern was in place nine weeks after conception, with more coils at the baby's end than the placental end; this may be a response to your baby's movements. The cord contains three blood vessels: two arteries taking deoxygenated blood and waste from your baby to the placenta and one vein carrying oxygen-rich blood from the placenta to the baby. The cord diameter is usually less than 3/4 in (2 cm) and the blood vessels are embedded in and protected by a layer of jelly. The watery composition of the jelly, together with the cord's coiling pattern, prevents compression of the cord.
After the birth, your doctor will check the number of vessels in the cord since in 1 percent of singleton pregnancies the cord contains only one umbilical artery.