After birth, blood flow in the umbilical arteries and veins usually continues for a few minutes. The additional blood volume transferred to the baby during this time is known as placental transfusion. Immediate clamping of the umbilical cord has traditionally been recommended as part of active management of the third stage of labour, together with a prophylactic uterotonic drug and controlled cord traction, to reduce postpartum haemorrhage. Use of a prophylactic uterotonic drug clearly does reduce the risk of major haemorrhage. The timing of cord clamping does not appear to have a major impact on blood loss at the time of birth.
A difficulty in reviewing this subject is that different terminology and definitions have been used in different studies. This paper suggests that the term ‘immediate cord clamping’ be used to mean that this is done within 30 seconds of the birth of the baby. The definition ‘deferred cord clamping’ means not clamping until at least 2 minutes after delivery. The developers prefer the term ‘deferred’ (because it suggests a planned policy) to the previously used ‘delayed’, which might be felt to imply later than ideal. Those definitions leave clamping of the cord between 30 seconds and 2 minutes unclassified, which might be called intermediate timing of cord clamping. However, when possible in this paper the developers will clarify the definitions used in each study. In any case, during clinical maternity care, the ideal is to simply document the time that the umbilical cord is clamped rather than an artificial classification.
The role of ‘immediate’, rather than ‘deferred’, cord clamping has not been universally accepted as part of the active management of the third stage of labour and the optimal timing for cord clamping is unclear. For example, a survey of policy at 1175 units in 14 European countries found that two-thirds clamped the cord immediately after birth, although 90% routinely administered prophylactic uterotonics. The International Federation of Gynecology and Obstetrics and the World Health Organization (WHO) no longer recommend immediate cord clamping as a component of active management. Current guidance from the RCOG is that ‘The cord should not be clamped earlier than is necessary, based on clinical assessment of the situation.’ The WHO states ‘Late cord clamping (performed after 1 to 3 minutes after birth) is recommended for all births while initiating simultaneous essential newborn care … Early cord clamping (<1 minute after birth) is not recommended unless the neonate is asphyxiated and needs to be moved immediately for resuscitation.’ For healthy women with term births, the National Institute for Health and Care Excellence (NICE) recommends that the cord is not clamped in the first 60 seconds, except where there are concerns about the cord’s integrity or the baby’s heart rate. They recommend that the cord should be clamped before 5 minutes, although women should be supported if they wish this to be delayed further.
This opinion paper summarises the physiology of placental transfusion and reviews the evidence related to the timing of umbilical cord clamping.
Green-top Guideline No. 52: Prevention and Management of Postpartum Haemorrhage contains updated advice on the timing of cord blood clamping.