The umbilical cord is the connection between your baby and the placenta and, as such, plays an important role in keeping your baby healthy.1 However, on occasion, things can go wrong with the umbilical cord, such as it growing too long, not forming a good connection with the placenta or becoming knotted. Luckily, most umbilical cord conditions won’t harm your baby; however, in some cases, you may be recommended a c-section to keep your baby safe.
Below are some of the potential problems you may experience with an umbilical cord.
Single umbilical artery
Normally, an umbilical cord consists of one vein and two smaller arteries but, occasionally, it may develop with only one artery. This occurs in around 1 in 100 singleton pregnancies (just one baby) and about 5 in 100 multiple pregnancies (twins, triplets, or more).2 Single umbilical artery is found more often in white women than in black or Japanese women and also occurs more often in women with diabetes.3 The cause of single umbilical artery is unknown.
Most babies (80%) with a single umbilical artery will be born perfectly healthy. However, for 20% babies of babies with a single umbilical artery, cardiovascular disorders, gastrointestinal disorders, renal defects, and genetic conditions, such as trisomy 18, may be present. If an ultrasound shows you may have a single umbilical artery, you may be recommended to undergo:
- Amniocentesis to check for birth defects and genetic decisions
- A detailed ultrasound to assess your baby’s anatomy
- An echocardiogram to check your baby’s heart2
Vasa previa is a condition when one or more blood vessels from the umbilical cord cover the cervix. These vessels are at risk of tearing during labor because they aren’t protected by the umbilical cord or placenta. This may lead to life-threatening bleeding in your baby, with torn blood vessels resulting in the death of around half of babies with vasa previa. If vasa previa is found either during a pelvic examination or on an ultrasound, you may be recommended to have a c-section. Fortunately, vasa previa is rare, affecting only 1 in 2,000 to 3,000 births.
You may be more at risk of vasa previa if you:
- Have placenta issues, such as a low-lying placenta which fully or partially covers the cervix (placenta previa)
- Are carrying more than one baby
- Have an umbilical cord that doesn’t connect properly to the placenta (velamentous insertion)2
Cord knots, nuchal cord and cord constriction
Cord knots occur most often when the cord is too long or in twin pregnancies which share one amniotic sac, making it easy for the two cords to get tangled. They tend to form early on in pregnancy when the baby is most active in the womb and occur in around 1 in 100 pregnancies. Cord knots can be dangerous if the knot tightens and cuts of oxygen to your baby and a c-section may be recommended, depending on how far along the pregnancy is.3
A nuchal cord is one which has become coiled around different parts of the baby, most commonly the neck. Nuchal cords occur relatively frequently – around 20% of babies experience one loop of the cord around the neck and around 5% experience multiple loops around the neck. Luckily, nuchal cords seldom lead to stillbirth and consequently no intervention is usually required.
Cord stricture is when the cord is partially or wholly blocked and has been found to occur in up to 19% of stillbirths. Unfortunately, this condition cannot be diagnosed by ultrasound.3