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Why do obstetricians and midwives still rush to clamp the cord?

BMJ 2010; 341 doi: https://doi.org/10.1136/bmj.c5447 (Published 11 November 2010) Cite this as: BMJ 2010;341:c5447

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Part 2 Neonatal asphyxia birth research

Briefly the argument can go as follows:

The pathology. Neonatal asphyxia is a serious condition often resulting in serious morbidity and death. It is due to hypoxia of the fetus developing during labour and is the result of reduced oxygen transfer from the placenta. Normally, immediately after birth, there is a transition from oxygenation by the placenta to the neonatal lungs as they take over when the neonate starts to breathe.

The theory. From general observation over thousands of years and more recent scientific investigation, this transition is known to take place over a few minutes. (Farrar et al 2009), (Wiberg et al 2008) . In the majority of newborn infants who do not breathe sufficiently, gentle assistance to make the transition from placental to pulmonary gas exchange may be all that is necessary. (Morely and Davis 2008) It is expected that if the failure to breathe can be corrected by ventilation of the lungs then the pathology will be reversed. Farrar et al (2009) also showed that there can be over 163 mls of blood trapped in the placenta by early cord clamping which would render the neonate hypovolaemic. In addition Wiberg et al showed that there is a high level of oxygen in the blood returning from the placenta in the first few minutes and this could sustain the neonate and supplement the oxygen delivery to the baby's brain during transition.

Animal studies support the theory. (Dawes 1968). Dawes stated, from his animal studies, that the fetal brain is remarkably resistant to damage by hypoxia and maintenance of the circulation during asphyxia was one major factor which prolonged survival. He was able to show that in the sheep model the brain could survive total hypoxia of 40 minutes with recovery when the oxygen supply was restored, provided the circulation had been maintained. He showed that the heart can continue to function for this period of anoxia as long as there is a sufficient store of cardiac glycogen for anaerobic metabolism. After restoring oxygenated blood, the fetal lamb began to make respiratory and limb movements. He reported that "Although this did not prove that no permanent damage had been done, it suggests that the vital organs were still intact." However he also reported that once the heart began to fail and circulation of the brain was affected, irreversible brain injury took place. A similar proposition is recommended in adult resuscitation (Resuscitation Guidelines UK 2010) since it considered that maintaining the circulation by extra-cardiac massage is more important than ventilation of the lungs. http://www.resus.org.uk/pages/guide.htm

When the cord is tied in fetal lambs, the heart rate falls almost at once from a rate of about 200bpm to less than 100 bpm.( Dawes 1959 ) Cord compression is well recognised to result in fetal bradycardia (Calderyo-Barcia 1963),( Arellano-Hernandez 1963) Early cord clamping has been shown to have the same effect. (Brady and James 1962) A recent study by Dawson et al (2010) has shown that the "normal range" of heart rate may be lower than was previously reported. All these babies had early cord clamping. (Personal communication)

The hypothesis. A low Apgar score was strongly associated with cerebral palsy. (Kveim Lie etal 2010) Since early cord clamping may lead to a low Apgar, more intervention may be necessary. Neonatal resuscitation does not completely restore health even in those that respond well. (Odd et al 2009) If the baby is in better condition at birth with a better circulation and less bradycardia, there will be less perception of the need for resuscitation and less risk of complications of resuscitation such as pneumothorax. The hypothesis is that the baby will recovery from intrapartum hypoxia more quickly and need less ventilation if the placental circulation is not interrupted artificially. This is supported by the recent work of Wiberg et al who reported three cases of significant intrapartum hypoxia in babies who recovered without any intervention while the placental circulation continued.Keeping the placental circulation intact would also be expected to prevent the rare catastrophic events of severe hypovolaemia and asystole proposed by Mercer et al. (2009) There will be less perinatal mortality and less long term morbidity such as cerebral palsy.

Heart rate is now considered one or the most important measures of neonatal health in the first minute after birth so it is particularly important that there is no unnecessary intervention which might lower the heart rate. As cited above early cord clamping may be a cause of bradycardia. Currently the greatest effort is being directed at identifying hypoxia in labour by improving the interpretation of the cardiotocograph. (CMACE 2010) Logically it is thought that during labour, if significant hypoxia is identified early enough, immediate delivery of the baby will shorten the time and reduce the depth of hypoxia experienced by the neonatal brain. The logical thought behind initiating resuscitation without artificially removing the placental circulation is to take advantage of the placental oxygenation which will supplement pulmonary circulation during resuscitation and thus shorten the severity of hypoxia. These two approaches obviously complement each other rather than compete with each other. In avoiding early cord clamping, hypovolaemia which is an inevitable consequence of early cord clamping, is prevented. When hypovoalemia is severe hypoxic ischemia of the cerebral circulation is almost inevitable.

In addition to volume there are also numerous stem cells in the placental transfusion which has been considered to be mankind's first natural stem cell transplant. The maturation of every organ system continues after the neonatal period; thus the artificial loss of stem cells at birth could potentially impact later development and predispose infants to diseases such as chronic lung disease, asthma, diabetes, epilepsy, cerebral palsy, Parkinson's disease, infection and neoplasm. Autologous stem cell transplants are under investigation for the treatment of HIE. (Hypoxic Ischemic Encephalopathy Study)

I will provide the details of the necessary human study in a further response.

Competing interests: DJRH organised a meeting, hosted at Worcester Royal Infirmary by Andrew Gallagher, to discuss how resuscitation with the cord intact could be initiated at the different modes of delivery, spontaneous delivery, assisted vaginal delivery, and caesarean section. This meeting coined the acronym BASICS to describe the concepts of a trolley that could be developed to provide the resuscitation equipment. DJRH and others at the meeting signed up to ownership of this intellectual property, but DJRH doesn't expect any financial or other gain from this ownership.

03 December 2010
David JR Hutchon
Retired obstetrician
Memorial Hospital, Darlington