new born infant in the operation room

Your Baby’s Umbilical Cord

The umbilical cord – also referred to as the birth cord, connects the developing baby to the placenta (afterbirth). The cord literally acts as a ‘life line’ supplying the baby with oxygen and nutrients that support its growth and development whilst they are in the uterus (womb).


What does the umbilical cord look like?

In a baby that is born at term (around their due date), the cord has a spiral twist and is normally around 50-60 cm long, with a diameter of approximately 1-2 centimetres. The length of the umbilical cord enables the baby to pass down through the pelvis and be born vaginally without any traction being applied to the placenta. Where the umbilical cord is longer than usual it can become wrapped around the baby’s neck and/or body, and, very rarely, become knotted. A cord can also be shorter than would be expected, with studies showing that this can sometimes affect the baby’s growth in the uterus (called fetal growth restriction).

The outer surface of the cord is a dull bluish-white colour and is soft and moist. It normally comprises two umbilical arteries and one umbilical vein which originate from the placenta. The arteries and vein are encased in a protective, jelly-like substance known as Wharton’s jelly, which is covered by placental membrane called amnion. Once your placenta has been delivered by the midwife or doctor, it is checked to ensure it is healthy and complete. In some cases, examination of the umbilical cord will reveal that there are only two blood vessels present – one vein and one artery. This can sometimes suggest a problem with the baby’s development from birth – called a congenital abnormality; however, finding two vessels in the cord can also be completely harmless!


How does the umbilical cord work?

The umbilical cord is formed by the fifth week of pregnancy and is attached to the placenta, which transfers oxygen, nutrients and waste products, such as carbon dioxide (CO2) to and from the mother’s blood circulatory system without there being any direct contact between the mother’s and baby’s blood. The blood vessels in the umbilical cord operate differently from what would normally be expected ie in the human body veins carry deoxygenated blood (blood not containing oxygen) to the heart and arteries carry oxygenated blood (blood containing oxygen) from the heart. However, while the baby is in the uterus, the umbilical vein provides the baby with oxygenated blood and nutrients which it carries to the baby’s heart. The two umbilical arteries carry away the deoxygenated and nutrient-depleted blood.

The umbilical cord enters the developing baby through its lower abdominal wall, at the level which, once it separates post birth, becomes the baby’s umbilicus, navel or ‘tummy button’!

Close up of a fresh human placenta


Umbilical cord insertion into the placenta

In the majority of cases the umbilical cord is inserted at, or close to, the centre of the placenta. However, sometimes the cord will be inserted into the placenta in a less common/abnormal position which has the potential to cause problems that can affect the mother’s and/or her baby’s health and well-being. Different types of cord insertion include the following:

Battledore insertion – where the cord is attached at the very edge of the placenta

Velamentous insertion – in around 1% of cases, the cord originates in membranes away from the edge of the placenta and the cord vessels run through the membranes to reach the placenta. There is a danger that spontaneous rupture of the membranes (SRM) – the ‘waters breaking’ can be accompanied by tearing of a cord vessel and bleeding

Vasa praevia – this is a condition that is associated with velamentous insertion (as above). It is where some of the fetal blood vessels in the membranes lie across the cervical os (neck of the womb) below the baby’s head. This can cause severe bleeding if the membranes rupture or the cervix starts to dilate.


Physiological changes to the cord following birth

Once the baby has been born, their umbilical cord is exposed to the cooler temperature of their new environment. This drop in temperature causes the Wharton’s jelly to swell and compress the blood vessels within it, which results in a natural clamping effect that curbs the blood flow. Where this process is allowed to continue without intervention, the blood flow will usually stop on its own within 5-20 minutes post birth. However, in water births the temperature of the water can be equal to the temperature inside the womb and so the umbilical cord may continue to pulsate for five minutes or longer. See also our article ‘Waterbirth: Immersion in water for labour and/or your baby’s birth’.

Newborn baby on the balance


Artificial clamping of the cord & Active management of the Third Stage

Active management of the third stage of labour has been favoured by doctors and midwives for decades – see also our article ‘Delivering your placenta – The third stage of labour’. Active management involves the early clamping and cutting of the umbilical cord; giving the woman an intramuscular (IM) injection of syntometrine into the top of her leg (which makes the uterus contract), and delivering the placenta by controlled cord traction (CCT). Clamping of the cord can be undertaken as early as one minute post birth, or even sooner, with studies showing that this is frequently done within 10-30 seconds of the baby’s birth. There are situations however, where immediate clamping/cutting of the cord is necessary; these include obstetric emergencies and preterm births where the baby is born in poor condition and needs immediate resuscitation (help with their breathing).


Delayed cord clamping

Delayed cord clamping and the associated health benefits to the baby have been discussed widely. Studies show that delayed clamping of the umbilical cord in term babies, for at least two minutes post birth, improves their haemoglobin levels (iron count) and reduces the risk of anaemia. The blood also helps to fill the blood vessels around the baby’s lungs which help them to breathe independently. However, studies have also found an increased risk of neonatal jaundice requiring phototherapy, where cord clamping was delayed in excess of 60 seconds post birth. See also our article – ‘Jaundice in the newborn (neonatal jaundice)’. However, where the jaundice did not require treatment with phototherapy no difference was found between early and delayed cord clamping.

Delayed cord clamping is particularly used in premature births where the baby is born in good condition – allowing more blood to flow into the baby naturally from their placenta.


Physiological Third Stage of Labour

Women with uncomplicated pregnancies may choose a more natural approach and might request to have clamping and cutting of the cord delayed by five minutes or longer, or have it omitted altogether in favour of having a Physiological (natural) third stage. Having a physiological third stage allows the mother to hold her newborn baby skin-to-skin while the baby is still attached to its umbilical cord and the placenta inside the uterus. The cord is allowed to stop pulsating on its own, without intervention, and, as the uterus contracts, the placenta shears off/comes away from the uterine wall. Having a physiological third stage can take anything between 10 min and one hour following the baby’s birth. For more detailed information see our article, Delivering your placenta: The third stage of labour’.


‘Lotus birth’

A lotus birth is where the umbilical cord is not cut at birth and is left entirely intact and attached to the placenta. The cord is left to dry naturally and tends to separate and fall off between the third to tenth day post birth, leaving a healed umbilicus. The use of oils, herbs and salt to help keep the placenta sweet smelling and to help it dry out are usually recommended. Lotus birth is a lot less common than both active management and physiological third stage. If Lotus birth appeals to you, your midwife or doctor will be able to discuss this option with you in more detail.


Cutting the cord

Where the umbilical cord is clamped, this is then followed by cutting it. Severing the cord does not hurt the baby because there are no nerves within the cord. However, because the Wharton’s jelly is so gelatinous, the cord has a thick, tough sinewy quality that requires special cord scissors to cut through it effectively. Where the umbilical cord is cut after it has ceased pulsating (usually 5-20 minutes post birth), there should be no significant loss of cord blood.

baby cord and clampOnce the cord has been clamped and cut, a small plastic clip is put in place which allows the compressed section of the cord to dry out and seal. The remaining umbilical stump becomes dry and turns a black colour; following a process of aseptic necrosis (dry gangrene), it usually separates and falls off around 7-10 days post birth. During this process, you may notice a slight odour from the cord; this is caused by bacteria that are normally found on the surface of the skin. You may also notice a very small amount of bleeding around the cord stump – this is a normal part of the separation process. Research studies have found that there is no evidence to support the use of antiseptic preparations on the umbilical cord, consequently, the use of sterile talcum powder and alcohol swabs was stopped a long time ago. You will however, need to maintain good hand hygiene and ensure that you avoid handling the cord during nappy changes. This helps to ensure that the natural process of aseptic necrosis is not interrupted. However, should the umbilical cord becomes soiled with baby ‘poo’ or urine and the area needs to be cleaned, this should be undertaken using plain tap water and cotton wool, after which the cord should be dried carefully.


Umbilical flare

An umbilical flare is where there is inflammation of the skin around the base of the umbilical cord; this is usually caused by infection. A very ‘offensive’ (smelly) discharge may also be noticed. Where this happens it is important that you contact your midwife or doctor immediately for their advice. They are likely to take a swab of the area and if this shows infection, the doctor can prescribe antibiotics for the baby. If there is any unexplained excessive bleeding from the umbilicus, this could indicate there is a problem with the baby’s blood clotting mechanism – called vitamin K deficiency bleeding (VKDB), formerly known as haemorrhagic disease of the newborn (HDN). Where there is any bleeding you should always seek medical advice without delay. See also our article ‘Vitamin K for your newborn’.

Should you have any queries or concerns about any of the above, we always recommend that you speak to your own midwife and doctor who can discuss these with you in more detail.

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