I used to think that delayed (or ‘deferred’, as is now the preferred term, in order to avoid any suggestion of suboptimal care) cord clamping was a waste of time, and more likely to cause harm than good, but now I realise that I was wrong.
Readers of this journal will know that when cord clamping is deferred for a few minutes, the newborn baby receives an additional transfusion of blood from the placenta of 80–100 ml (Farrar et al, 2011). This is quite a significant volume, bearing in mind that a 3.5kg fetus (i.e. just before birth) has a blood volume of around 250 ml (Dawes, 1968; Farrar et al, 2011). And in the preterm baby, this proportional increase is greater, as a greater proportion is sequestered in the placenta. This has been shown to result in a reduced chance of iron deficiency (although no difference in haemoglobin concentration) at 3–6 months of age. It also results in an increase in the chance of jaundice in the first few days after birth, as the extra red blood cells are broken down, releasing bilirubin into the baby's circulation (McDonald et al, 2013). So my view was along the following lines: less iron deficiency but more jaundice seemed fairly evenly balanced, but delaying active management of the third stage would increase the risk of postpartum haemorrhage (PPH) in the mother, thereby increasing the risk to her with little net benefit to the baby. I had done much of my research in the prevention of PPH, and had worked and lectured regularly in India and Africa and witnessed first hand the terrible toll PPH can take.
Active management
Active management of labour is effective; it reduces the chances of PPH by around two thirds (Westhoff et al, 2013). But what I had wrongly assumed was that active management required the whole package (early uterotonic administration, early cord clamping, and controlled cord traction) to be effective. What I failed to appreciate, and what has now been conclusively shown in the most recent Cochrane review of this topic (McDonald et al, 2013), is that while uterotonic drugs are indeed effective at preventing PPH, the timing of cord clamping makes no difference to the blood loss.
Deferred clamping policy
To my mind, this knowledge shifts the balance in favour of deferred cord clamping. In other settings there is an association between iron deficiency in infancy and neurodevelopmental delay (although this hasn't been shown in the context of deferred cord clamping in otherwise healthy babies—the lack of long-term follow-up studies to date is striking). And, for every 100 babies in whom cord clamping is deferred, only two extra will need phototherapy for jaundice (McDonald et al, 2013). And, most importantly, if there is no harm, it seems sensible to follow nature's way and not interfere with that placental transfusion; nature usually has good reasons! There are, for example, some animal studies that suggest that the extra blood may help the fetus make the transition more effectively from a fetal to a neonatal circulation. The Royal College of Midwives, Royal College of Obstetricians and Gynaecologists, International Federation of Gynecology and Obstetrics, National Institute for Health and Care Excellence and the World Health Organization are now unanimous in their advice to defer cord clamping unless there is a particular indication to clamp early (Duley et al, 2014); deferred cord clamping is now the default.
Use of uterotonic drugs
There are a few important practical implications of this policy. While the cord is unclamped, the cord blood gas values change, making them more difficult to interpret. So it is very important for both clinical and medicolegal reasons to record the time the cord is clamped. Parents who wish to collect cord blood for stem cell storage should be advised that deferred clamping is likely to result in a reduced volume being collected. Most important, perhaps, is that with the cord unclamped, the position of the baby becomes more important. Without the use of an oxytocic drug, if the baby is just 20 cm above the level of the placenta, it can have a substantial effect on the amount of blood transfused. Bear in mind that the blood in the umbilical arteries (which have relatively high pressure) will continue to flow out of the baby to the placenta, while the blood flow through the umbilical veins (which have low pressure) will be significantly reduced by the effect of gravity. Given that most babies are immediately put onto their mother's breast or into her arms, this may be important. The use of an oxytocic drug will ‘squeeze’ the blood from the placenta into the baby, and help to overcome the effect of gravity. This may be even more important following Caesarean section, when the baby is often held higher so the parents can see it above the sterile screen, although this extra gravitational effect may be counteracted by the fast-acting intravenous oxytocin that is usually given at Caesarean. Unfortunately, there is still little research on the exact interaction of uterotonic drugs, gravity and timing of cord clamping, although it is now urgently needed. But it may well be that when cord clamping is deferred, rather than avoiding uterotonic drugs to keep the birth as natural as possible, an oxytocic drug should be used, not just to reduce the risk of PPH in the mother, but also to ensure that the baby held up in its mother's arms does indeed receive the placental transfusion that deferred clamping is aiming to achieve.