Until recently, standard practice in most labour wards was to clamp and cut the umbilical cord immediately after birth. However, more recently, evidence has emerged to support the idea that delaying the clamping of the cord could have beneficial effects for the baby.
At birth, the flow of blood through the umbilical cord usually continues for a few minutes. The additional blood transferred to the infant during this time is known as placental transfusion. For a full-term infant, placental transfusion gives the infant an additional 80–100 ml of blood.
Very quickly, the additional plasma from the placental transfusion is broken down into iron and stored in the baby. Therefore, reducing placental transfusion by immediate cord clamping can deprive the baby of 20–30 mg/kg of iron, sufficient for the needs of a newborn infant for around 3 months.
The flow of blood from the placenta to the baby is affected by a few factors, such as; how hard the placenta is squeezed by the uterus after the birth of the baby, how far the baby is held below or above the placenta during this time and how long before the cord is clamped.
The definition of delayed clamping is not entirely obvious as it varies from study to study, from 2 to 5 minutes or when the placenta ceases to pulsate or is delivered.
Raising the baby above the level of the placenta will reduce blood flow to the baby, and conversely, lowering the baby below the level of the placenta speeds flow to the infant but without apparently influencing the net volume of placental transfusion. The impact on this blood flow, of placing the baby on the mother’s abdomen or thighs is as yet, unknown.
In trials, results showed that at birth, the babies in the immediate cord clamping group had lower haemoglobin levels than those in the deferred clamping group – although this difference was not statistically significant at 2–4 months of age. Babies with immediate clamping were more likely to be transfused for anaemia than those in the deferred clamping group.
It should be noted however, that results showed that those babies whose cords were clamped immediately had a lower relative risk of being given phototherapy treatment for jaundice.
Results showed that if you are given an injection of a uterotonic drug (as is commonly recommended) to help deliver the placenta and reduce the risk of excessive bleeding, it is not likely to have a substantive effect on this placental transfusion. However, further research needs to be done to confirm whether there is a clinically relevant effect on either volume or flow.
Premature babies present a special case as early clamping of the cord is associated with increases in brain haemorrhage and also the need for blood transfusions.
Although more research is needed to assess the full and long-term impact of delayed clamping on both mother and baby, the general conclusion is that early clamping is not longer routinely recommended. However, practice will vary from hospital to hospital, so if this is something you feel strongly about then you must discuss the options with your midwife or doctor before your birth.