It's the thing that people talk about if it happened to them, and when they do they say it was pretty frightening. And perhaps it's talked about so often because nuchal cords are fairly common.
Nuchal cord prenatal diagnosis
Parents who have a late-pregnancy ultrasound scan may be told that their baby has a nuchal cord. This may cause them to panic, but unnecessarily. There is no evidence that a cord wrapped around a baby's neck during pregnancy causes adverse outcomes (ie, stillbirth). In up to 50 percent of cases, the nuchal cord will resolve itself before labor and birth roll round. The average umbilical cord is 55 cm long making it longer than the height of the average newborn. It is normal for the cord to move in all kinds of directions during pregnancy, as the baby moves.
In many cases, a cord will end up round the baby's neck. This does not compromise the baby's oxygen supply. Some stillborn babies will be born with their umbilical cord around their neck. Healthcare providers may even offer this as an explanation for the baby's death. However, stillborn babies appear to have nuchal cords at the same rate as other babies in up to one third of cases. There is nothing to suggest that a nuchal cord is in any way responsible. In short, there is nothing to worry about if your baby was shown to have a nuchal cord at an ultrasound scan. More rigorous monitoring during and immediately after birth may, however, be in order.
Cord around the neck during labor and delivery
Is a nuchal cord dangerous during labor and delivery then? In short, the answer is "sometimes". Let's tackle labor first. During labor, the top of the uterus, the placenta, the cord and the baby all move down together at the same rate. A nuchal cord does not prevent the baby from moving down into the cervix and through the vagina for that reason.
As a baby with a nuchal cord is being born, the cord remains around the baby's neck. Up to a third of all babies will have their umbilical cord around the neck at birth. Nuchal cords seem to strike boys more often than girls, perhaps boys tend to have longer umbilical cords too. Midwives report that the cord will typically be wrapped around the baby's neck loosely, and that it can simply be slipped off. This is where we should note that there are two types of nuchal cords loose nuchal cords and tight nuchal cords.
Loose nuchal cords do not compromise the baby's blood supply and is not an emergency of any kind. This is nothing to write home about (or to broadcast and scare other moms with) for this reason. In some cases, the nuchal cord will wrap around the baby's neck more tightly. In these cases, the cord will stretch while they baby is being born, and less blood will pass through it. The baby's oxygen supply is then temporarily compromised (hypoxia).
This can be dangerous and requires immediate attention. Usually, there are no long-term problems at all though and the baby just needs a little longer to perk up. Some nuchal cords actually create a true knot within the cord. Unlike your traditional "cord wrapped around baby's neck", a true knot can be very dangerous, whether the cord is still around the neck or not. As the baby emerges from the birth canal during delivery, these knots can be pulled taut and the baby's oxygen supply can be compromised. Every hospital has policies on how to deal with all types of complications during labor and delivery. It is always good to find out how your doctor or midwife will deal with a nuchal cord. Discuss this in some detail, so that you won't panic if it does happen to your baby during labor and birth. You may also be interested in reading: Why practice delayed cord clamping after birth?