The timing of umbilical cord clamping at birth: physiological considerations

Hooper et al. Maternal Health, Neonatology, and Perinatology (2016) 2:4 DOI 10.1186/s40748-016-0032-y Maternal Health, Neonatology, and Perinatology REVIEW Open Access The timing of umbilical cord clamping at birth: physiological considerations Stuart B. Hooper1,2*, Corinna Binder-Heschl1, Graeme R. Polglase1,2, Andrew W. Gill3, Martin Kluckow4, Euan M. Wallace1,2, Douglas Blank1,5 and Arjan B. te Pas6 Abstract While it is now recognized that umbilical cord clamping (UCC) at birth is not necessarily an innocuous act, there is still much confusion concerning the potential benefits and harms of this common procedure. It is most commonly assumed that delaying UCC will automatically result in a time-dependent net placental-to-infant blood transfusion, irrespective of the infant’s physiological state. Whether or not this occurs, will likely depend on the infant’s physiological state and not on the amount of time that has elapsed between birth and umbilical cord clamping (UCC). However, we believe that this is an overly simplistic view of what can occur during delayed UCC and ignores the benefits associated with maintaining the infant’s venous return and cardiac output during transition. Recent experimental evidence and observations in humans have provided compelling evidence to demonstrate that time is not a major factor influencing placental-to-infant blood transfusion after birth. Indeed, there are many factors that influence blood flow in the umbilical vessels after birth, which depending on the dominating factors could potentially result in infant-to-placental blood transfusion. The most dominant factors that influence umbilical artery and venous blood flows after birth are lung aeration, spontaneous inspirations, crying and uterine contractions. It is still not entirely clear whether gravity differentially alters umbilical artery and venous flows, although the available data suggests that its influence, if present, is minimal. While there is much support for delaying UCC at birth, much of the debate has focused on a time-based approach, which we believe is misguided. While a time-based approach is much easier and convenient for the caregiver, ignoring the infant’s physiology during delayed UCC can potentially be counter-productive for the infant. Keywords: Delayed umbilical cord clamping, Birth, Neonatal cardiovascular transition, Umbilical artery flow, Umbilical venous flow Background The transition from fetal to newborn life represents one of the greatest physiological challenges that any human will encounter. Once the umbilical cord is clamped, infants must clear their airways of liquid to allow the onset of pulmonary gas exchange and the cardiovascular system must undergo a major structural and functional re-organisation [1]. Although it is well recognized that the cardiovascular transition at birth is triggered by lung aeration [2, 3], the question of how umbilical cord clamping (UCC) influences this relationship is unclear * Correspondence: 1 The Ritchie Centre, Hudson Institute for Medical Research, Melbourne, Australia 2 Department of Obstetrics and Gynaecology, Monash University, Melbourne, Australia Full list of author information is available at the end of the article [1]. It is widely assumed that UCC at birth is an innocuous act, but many have argued that this assumption is false and, if done too early, can deprive the infant of vital blood volume during early newborn life [4, 5]. The aim of this review is to discuss the physiology of umbilical cord clamping and the circumstances that would facilitate placental transfusion if UCC is delayed. At birth, lung aeration triggers a functional reorganisation of the infant’s circulation, largely by stimulating an increase in pulmonary blood flow (PBF) [1]. From a teleological perspective, linking these physiological events is logical. As lung aeration can only occur after birth and is a pre-requisite for newborn survival, it is an ideal trigger for initiating the physiological changes that underpin the transition to newborn life. In this context, when trying to © 2016 The Author(s). Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Hooper et al. Maternal Health, Neonatology, and Perinatology (2016) 2:4 Page 2 of 9 understand and devise strategies that assist the infant in making the best possible transition to newborn life, it is important to understand the central role that lung aeration plays in this process. Indeed, neonatologists have long recognized that, at birth, ventilation is the key to newborn resuscitation. It not only increases oxygenation, but also increases the infant’s heart rate and cardiac function by stimulating an increase in PBF [3]. An increase in PBF restores the preload required to maintain cardiac output after birth (Fig. 1), which is lost upon umbilical cord clamping (UCC) [6, 7]. In view of the central role that lung aeration plays in the cardiovascular transition at birth, it is also likely to have a major impact on placental to infant blood transfusion when UCC is delayed. However, until recently all arguments about delayed UCC have simply focused on the time that UCC should be delayed with little or no reference to the infant’s transitional physiology [5]. In this review, we will argue that there is little or no justification for delaying UCC for a set period of time after birth and will discuss physiological factors that may provide a more rational determinant for when UCC should occur after birth. Aristotle in 300 BC. In 1801, Erasmus Darwin suggested that, ‘Another thing very injurious to the child, is the tying and cutting of the navel string too soon; which should always be left till the child has not only repeatedly breathed but till all pulsation in the cord ceases. As otherwise the child is much weaker than it ought to be’ [8]. In this commentary, Darwin highlights the link between breathing and the timing of UCC, indicating that he considered the two events to be closely linked and to impact on the infant’s well being. However, the debate about the timing of UCC at birth has largely overlooked the impact that pulmonary ventilation may have in this process. Until recently, the benefits of delayed UCC at birth were thought to only involve placental-to-infant blood transfusion. This debate was sparked by a series of studies demonstrating a time dependent “transfusion” of blood into the infant if UCC is delayed for up to 3 mins after birth (...truncated)