How long should delayed cord clamping really be?
The story around cord management after birth continues to be an evolving one. I have certainly posted my own thoughts on this before with my most recent post being Delayed cord clamping may get replaced. Time for physiological based cord clamping. While this piece demonstrated that there are benefits to longer times till clamping is done, it also showed that if you go too long hypothermia becomes a real risk and with it possible complications. At least in our centre the standard that we have tried to reach is DCC for one minute for our infants. As you will no doubt know from the literature reviewed here before, this is likely not long enough!
One or Three Minutes?
This study caught my eye this week. Effect of early versus delayed cord clamping in neonate on heart rate, breathing and oxygen saturation during first 10 minutes of birth – randomized clinical trial What struck me in particular about this paper was not just the physiologic outcomes it was looking at. What is remarkable is the size of the study. So many articles that are published in Neonatology have under a hundred patients. On occasion we see studies with hundreds. In this case the authors included 1510 patients who were randomized to early ≤60 s of birth and ≥ 180 s for time of clamping. What is also interesting here is that early which used to be considered right after delivery of the infant is now 1 minute in this study. I like that this is the accepted new norm for this type of study.
Inclusion criteria were such that these were all low risk vaginal deliveries with fetal heart rate (FHR) ≥100 ≤ 160 bpm and all infants were ≥33 weeks. Although 1510 were randomized (power calculation for sample size found there should be 566 per group based on an expected loss of 25% per arm. In the end there were 670 in the ECC and 594 in the DCC groups that adhered to the protocol. In the ECC group the mean duration of time till clamping occurred was 31.2 s (+/-14.4) vs 198.5s (+/-16.9).
The goal after delivery is to increase blood flow to the lungs as PVR drops. In order to do so this requires adequate ventilation but it also requires adequate perfusion of the myocardium. If you clamp too early and pulmonary blood flow has not yet increased you run the risk of having a sudden drop in coronary blood flow with oxygenated blood from the placenta and with that bradycardia.
A longer time on “heart lung bypass” from the placenta should allow for a smoother transition. That is what was seen here. At 1, 5 and 10 minutes infants randomized to the DCC had better oxygen saturations. Heart rates interestingly were lower in the DCC group but that could also be related to better oxygenation leading to less compensatory tachycardia. In other studies in which the cord was clamped immediately bradycardia was more common. This difference here may reflect timing of the clamp on heart rate. Lastly, time to first breath was much faster in the group randomized to DCC. Might this be an effect of better oxygenation?
What they didn’t measure?
There was no comment on risk of hypothermia or other markers of illness such as rates of admission to NICU, hypoglycemia, lethargy or other markers of an infant who became cold. If this is to become standard practice measures need to be in place to prevent these concerns from becoming reality. It is also worth noting the population studied. These are healthy late preterm and term pregnancies. More work is needed on younger infants and those with risk factors in pregnancy. How would mothers with poor tracings, diabetes or hypertension fare as well as those who have growth restricted infants?
This field is growing and I will continue to follow this evolving story and share information as it becomes available. One thing in my mind is fairly certain though and that is that clamping right after delivery for routine births should be a thing of the past.