Delivery Room and Postnatal Assessment of the Physiological Effects of Deferred Cord Clamping on the Newborn: A Feasibility Study

Deferred cord clamping appears to confer short term benefits for both term and preterm newborn babies. However, the optimal timing of cord clamping remains unclear, it is increasingly being hypothesised that immediate cord clamping may be disrupting a physiological process. Indeed, differences in the anatomy and physiology of the baby and placenta may lead to functional differences potentially altering the blood flow to the newborn. This may have implications for the baby if the cord is clamped too early or too late. A method of estimating the best time to clamp the cord could offer both short and long-term benefits especially in the preterm population.

Many studies have started measuring the short-term benefits of deferred cord clamping such as reduced requirements for ventilation , red cell transfusions, improved perfusion and reduced incidence of intraventricular haemorrhage. Studies are currently underway examining the long-term benefits of deferred cord clamping. However, very little is known on the background physiology of placental transfusion. Studies often use arbitrary times for clamping the cord with little reference to a scientific basis. Many of the studies included in both Cochrane reviews and meta-analysis use a variable definition of deferred cord clamping varying from 30 seconds to 5 minutes or when the cord had stopped pulsating.

There appears to be very few risks associated with deferred cord clamping. There are some reports of an increased need for phototherapy to treat jaundice but this is not consistent. Polycythaemia is also reported, however, this is known to be present in a proportion of term deliveries regardless of the time of clamping and deferred cord clamping appears to confer no greater clinical risk with no change in the incidence of hypoglycaemia or increased need for exchange transfusion. In the preterm population once the baby has delivered there are issues relating to resuscitation that also need to be addressed. For example, a baby born at 25 weeks gestation may benefit from deferred cord clamping but this will alter the timing and approach of resuscitation. A better understanding of the physiology in these instances, coupled with a reliable measure of when the majority of the placental transfusion has occurred, may guide the optimal timing of cord clamping and the initiation of resuscitation.

Other methods of assessing placental transfusion have been tried and studies are currently ongoing including weighing infants during transfusion to measure the volume and speed of blood transfusion. However, it is difficult to transfer this method to the preterm population due to concerns regarding thermoregulation and need for resuscitation.

Although a number of studies investigating the effects of deferred umbilical cord clamping have been performed there is little research on the physiology behind placental transfusion. One study has previously used Doppler to assess blood velocity in the umbilical arteries although the methodology of this study is now outdated. This study was performed using sound Doppler recordings, which were then played via tape into a continuous spectrograph analyser. With the advancement of technology and the use of colour Doppler ultrasound it is possible to more reliably and quickly quantify umbilical cord blood flow therefore eliminating the methodological flaws of the above study. A few studies have examined the rate of placental transfusion although there has been disagreement as to whether the transfusion is a steady state or a rapid decrease over the first minutes after delivery. There is also little discussion as to whether timings are individual for each foetal-placental unit.