Am J Perinatol 2016; 33(11): 1032-1034
DOI: 10.1055/s-0036-1586121
Editorial
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

How and When Should We Clamp the Umbilical Cord: Does It Really Matter?

Nestor E. Vain
1   Foundation for Maternal Infant Health, Argentina
2   Department of Pediatrics, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
3   Department of Neonatology, Hospitals Sanatorio de la Trinidad, Palermo and San Isidro, Buenos Aires, Argentina
› Author Affiliations
Further Information

Publication History

Publication Date:
07 September 2016 (online)

Umbilical cord clamping is one of the most frequently performed medical or paramedical interventions: 131,000,000 times a year in the world (that means 250 times a minute). Any influence that the timing or the way in which the procedure is performed may have on the infant has the potential of an enormous impact on public health. In the last decade, a renovated interest on the subject led to the development of multiple clinical and physiological studies.

A Cochrane review on early versus delayed cord clamping (DCC) for at least 1 minute in term infants published in 2013 demonstrates clear benefits and minimal risks: a significant amount of blood flows from the placenta to the infant (placental transfusion) as can be inferred from the infants' weight increase: a mean of 101 g (∼96 mL of blood). Infants in the DCC groups have higher hemoglobin levels at 48 hours of life and a lower prevalence of iron deficiency in infancy. A potential negative finding is a slight increase in the need for phototherapy. Although an increase in maternal hemorrhage had been reported with DCC, the review rules out any maternal complications.[1] More recently, the evaluation of the same trials together with newer information led to the recent recommendation by International Liaison Committee on Resuscitation (ILCOR) of DCC for term infants born vigorous.[2]

However, the compliance with this recommendation appears limited. Some surveys report incomplete knowledge on the recommendations by physicians and a very high frequency of very early cord clamping in real practice.[3] [4] Besides the lack of knowledge, some reasons behind the use of early clamping may include that frequently health care workers act as if they were always in a rush, particularly in places with an interventionist attitude. In some cases, the collection of cord blood for banking (an unsupported practice when performed for individual use) leads to disregarding the recommendation of DCC. Another reason is likely to be that it is quite uncomfortable to hold for several minutes a just born infant at or below the level of the vagina until the cord is clamped. However, we recently demonstrated that if the baby is held by the mother on her abdomen or chest, gravity does not influence the volume of placental transfusion: DCC results in an almost identical placental transfusion to that of infants held at the level of the introitus.[5] Holding the infant by the mother immediately after birth potentially enhances bonding and successful breastfeeding. Still, surveillance of infants' position and breathing during those first minutes is essential.[6]

The impact of DCC in cesarean deliveries is less well understood. In a randomized controlled trial (RCT) the analysis of a subgroup of infants born through that route shows an increase in hematocrits at 48 hours when DCC is performed.[7] However, more recently, Katheria et al reported that in premature infants born by cesarean delivery, umbilical cord milking is more effective to increase placental transfusion when compared with DCC.[8]

Several RCTs analyzed the effect of DCC in premature infants. In 2015, ILCOR published the analysis of the available information. DCC decreased the risk of periventricular hemorrhage–intraventricular hemorrhage, the need for red blood cell transfusions, the incidence of necrotizing enterocolitis, and increased mean arterial pressure. Although the frequency of hyperbilirubinemia is increased, the consensus was to recommend DCC.[2]

Umbilical cord milking produces similar effects on placental transfusion when compared with DCC.[9] Its main potential advantage is that it is a brief procedure and may decrease the risk of heat loss and allow earlier resuscitation in immature infants when compared with DCC. However, in the way it was originally described, milking generates a very rapid and large blood transfusion, which implies potential risks.[10] The ILCOR 2015 experts committee placed a higher value on the unknown safety profile and less value on the simplicity/economy of this intervention. Furthermore, a recent study demonstrated large swings in blood pressure and carotid artery blood flow in an animal model of umbilical cord milking.[11] Interestingly, the potential advantage of milking over DCC to protect temperature stability in premature infants may not be real: a recent pilot trial by Backes et al in infants 22 to 27 weeks gestational age, demonstrates the efficacy of DCC and a higher temperature on arrival to the neonatal intensive care unit (NICU) when compared with immediate cord clamping.[12] The other potential advantage of milking is an earlier start of resuscitation. However, Katheria et al reported the feasibility to start resuscitation with an intact cord.[13] Several authors are currently investigating the potential advantages of this procedure.

Recent investigations in animals and physiological studies in humans brought up more light on the sequence of events and circulatory changes during birth and its relationship with the timing of cord clamping, initiation of breathing, and the position of the infant.

The first and seminal study by Bhatt et al compared the cardiovascular changes occurring in lambs in which the cord is clamped before lung expansion, to those in which it is clamped after ventilation has been initiated. In the first group, there is a brief and immediate rise in aortic and carotid blood pressure followed by a rapid decrease in left ventricular output and heart rate. When ventilation precedes cord clamping there is a smoother transition and no bradycardia.[14] The explanation for this difference is quite logical: cord clamping before breathing produces a brief increase in systemic blood pressure because of an increased resistance in the aorta due to interruption of umbilical artery flow, but subsequently, there is no blood return from the placenta to the infant. Pulmonary blood flow is minimal during fetal life, and left atrial filling derives from the placental blood return through the umbilical vein and the inferior vena cava. Therefore, blood flow to the left ventricle rapidly falls after clamping. When breathing is initiated before the cord is clamped, pulmonary blood flow immediately increases, allowing filling of the left atrium through the pulmonary veins. In this way the left ventricular output does not fall significantly and the cardiovascular transition becomes smoother. It is quite likely that some of the complications in extremely premature infants, in whom the cord is immediately clamped, including intraventricular hemorrhage, could be related to these abrupt changes in blood pressure and carotid blood flow.

Furthermore, in infants in whom asphyxia occurs, immediate cord clamping adds hypovolemia to the preexisting hypoxia: 30 to 50% of fetal circulation is located at the placenta. This situation may lead to a real hypoxic–ischemic event. Many recent and current studies and reviews by the Australian group of investigators are shedding light on these important issues.[15] [16]

But what should we then do when infants are not breathing immediately after birth? As I mentioned before, resuscitation with an intact cord is currently under investigation, and the answer in the case of clearly asphyxiated infants should wait for those results. Meanwhile, in premature infants who are electively delivered because of maternal or fetal risks, there is no reason to clamp the cord immediately after birth. The placenta is still doing its job providing continued gas exchange. Why then not wait until breathing is spontaneously initiated? The majority of those premature infants will start some breathing during the first minute and during that period some mild stimulation is feasible.[13] We can prevent heat losses, and in fact, normal temperature upon arrival to the NICU in extremely premature infants subjected to DCC has been demonstrated.[12] [13]

In summary, it appears wise to perform DCC in term and preterm infants. Some issues deserve further investigation, such as the approach to severely asphyxiated newborns and those with risk for polycythemia. However, we should strongly oppose the attitude of clamping the cord immediately because that is the way we have always done it or the way we have been taught. Ongoing studies on resuscitation at the bedside with an intact cord and physiological research in animals and humans will likely provide more rational answers. The period immediately before and after birth, and neonatal resuscitation are among the areas in medicine in which it is more difficult to perform clinical trials. The request for informed consent has been one of the major drawbacks. Other forms of reassurance of the ethics of those studies such as waivers or opt-out consents have opened up the possibility of obtaining this so badly needed information which is the basis for progress in the most crucial moment of human life.[17]

 
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