If the cord is cut before placental delivery then the exact timing becomes needlessly critical. Too early and the baby isn’t getting enough blood or oxygen. Too late and the baby might have TOO MUCH blood because of pressure on the placenta in the contracting womb. This could result in jaundice. The problem is compounded by a cerebral blood pressure spike that occurs at the moment of clamping if it happens before the heart’s transition to normal lung-respiratory blood flow.
The obvious solution is to wait AT LEAST until after placental delivery to allow natural (i.e. non-traumatic) separation from the uterine wall and correct blood volume transfer to the baby. The placenta might also release hormones and stem cells into the baby during placental delivery which could be important to long term health. And the mother’s body might get hormonal signals conducive to the postpartum process from the baby if the cord is left intact until natural mother-baby separation. We just don’t know, and we don’t need to know. Nature has this figured out already.
Intraventricular haemorrhage is a well recognised complication of preterm birth. Immediate cord clamping increases the risk of this haemorrhage (1,2) and has been implicated in other forms of brain damage.(3)
How can immediate cord clamping cause brain damage?
We have developed a computer model of fetal and adult pattern circulation. (4) The model shows what might happen when the functional umbilical circulation is suddenly occluded with early cord clamping. In fetal circulation the two sides of the heart work in parallel. 40% of the combined cardiac output (CCO) flows through the umbilical cord, while the pulmonary circulation is only about 18%. After birth, the neonate changes to an adult pattern circulation in which the two sides of the heart work in series. The output from each side is equal and is therefore 50% of the CCO of the fetus just before birth. All the output from the right ventricle passes through the pulmonary circulation.
The model clarifies what must happen when the cord is clamped before the pulmonary circulation is fully functional. When the cord is clamped 40% of the CCO must be proportionately redirected to the residual circulation. The systemic pressure almost doubles as does the cerebral circulation. The model shows that blood flow in the aortic isthmus must reverse as most of the flow through the ductus arteriosus is directed back up the aorta to the carotid arteries. Once the pulmonary circulation increases the abnormal cerebral and aortal flow returns to normal. However early cord clamping results in a loss of 40% of the cardiac return from the placenta and so shortly after the return to normal, the systemic blood pressure falls further as the cardiac output falls. If ventilation has started by this stage the pulmonary circulation greatly increases and flow through the ductus arteriosus virtually ceases, further reducing the systemic blood pressure. The filled capacity of the fully functional pulmonary circulation also reduces the circulating volume for the rest of the body….