At the time of birth, the infant is still attached to the mother via the umbilical cord, which is part of the placenta. The infant is separated from the placenta by severing the umbilical cord between two clamps. One clamp is placed close to the infant's navel and the second is placed further along the umbilical cord; then the cord is cut between the two clamps. This takes place during the third stage of labour, which is that period of time from birth of the infant until delivery of the placenta.

There are two contrasting approaches to managing the third stage of labour, active management and expectant or physiological management. A comparison of these approaches is the subject of a separate review (Prendiville 2002a). Expectant management is a non‐interventionist approach, which involves waiting for signs of placental separation and allowing the placenta to deliver spontaneously or aided by gravity, maternal effort or nipple stimulation. This strategy is popular in some northern European countries and in some units in the United States and Canada. It is also the usual practice in low income countries (McDonald 1996).

In contrast, active management involves the clinician intervening in the process through three interrelated processes; the administration of a prophylactic oxytocic drug; cord clamping and cutting; and controlled traction of the umbilical cord. An injection of an oxytocic drug, an agent that stimulates the uterus to contract, is given as a precautionary measure, aimed at reduction in the risk of postpartum haemorrhage. This injection is usually given to the mother at about the same time as the infant's shoulders are born. There are several different types of oxytocic drugs that may be given and the relative advantages and disadvantages of these different drugs are the subject of separate reviews (Elbourne 2002; McDonald 2002a; Gülmezoglu 2002; Prendiville 2002b; McDonald 2002b).

In an active management strategy the umbilical cord is usually clamped shortly following birth of the infant. At this time, the infant may be placed on the mother's abdomen, put to the breast or be more closely examined on a warmed cot if resuscitation is required. Once the placenta is felt to have separated from the wall of the uterus, downward traction may be applied to the remaining length of the umbilical cord to assist delivery of the placenta. Controlled cord traction is believed to reduce blood loss, shorten the third stage of labour and therefore minimise the time during which the mother is at risk from haemorrhage (McDonald in press).

Active management is widely practiced in high income countries, although relative timing of each individual component of the strategy varies. Most maternity units in Australia and the United Kingdom administer the oxytocic prior to placental delivery, whereas some units in the United States (Brucker 2001) and Canada (Baskett 1992) advocate withholding oxytocic administration until after the placenta is delivered.

A major reason for practicing active management is because it is associated with reduced risk of postpartum haemorrhage (PPH), the major complication of the third stage of labour (Prendiville 2002a). The usual definition of postpartum haemorrhage is that given by the World Health Organization (WHO): blood loss equal to or greater than 500 millilitres (ml) from the genital tract during the first 24 hours postpartum (WHO 1990; WHO 2000). Stricter definitions of 600 ml (Beischer 1986) and 1000 ml (Burchell 1980) have been suggested although the assessment of blood loss is often significantly underestimated and is based on a clinical estimation of blood loss (Kwast 1991; WHO 1998b). The 500 ml limit is intended to be a warning and blood loss up to 1000 ml in healthy women may still be considered physiological, not necessitating treatment other than oxytocics. In low income countries, where the prevalence of severe anaemia is high, a 500 ml blood loss can be life threatening for many women (WHO 1996). Postpartum haemorrhage is the most common fatal complication of pregnancy and childbirth in the world (UNICEF 2002). It is estimated to claim 150,000 lives annually (WHO 1990). Whilst the majority of maternal deaths (99%) occur in low income countries (WHO 2002), the risk of postpartum haemorrhage should not be underestimated for any birth (McDonald 2002b). Effects on maternal morbidity are less well documented, but are likely to include interrelated outcomes such as anaemia and fatigue (Patterson 1994). Complications that can arise from major blood loss include shock, the widespread formation of blood clots in the microcirculation, renal failure, liver failure and adult respiratory distress syndrome (Bonnar 2000)

Although active management leads to this reduced risk of PPH, it is important to establish which components of the strategy lead to this reduced risk. It can be difficult to adhere to an active management strategy. For instance, the strategy recommends that the oxytocic drug be given at the time of the birth of the anterior shoulder of the infant, whereas it is often given after delivery of the infant. This may be due to the number of staff available in the room at the time of birth and unexpected occurrences such as malpresentation (for example, a breech presentation) or shoulder dystocia (difficulty in delivering the infant's shoulders, McDonald 1996). Furthermore, some women have preferences for expectant management (McDonald in press). Thus, it is important to examine the relative importance of each component of an active management strategy.

The timing of umbilical cord clamping is one part of third stage management to consider. Options vary as to the most beneficial time for clamping the cord during the third stage of labour (Inch 1985). Early cord clamping, usually part of active management, is generally carried out in the first 30 seconds immediately after birth, regardless of whether the cord pulsation has ceased (McDonald 1996). Late cord clamping, or delayed clamping, a physiological approach, involves clamping the umbilical cord when cord pulsation has ceased. However, definitions of what constitutes early and late cord clamping vary (Prendiville 1989) and again, in practice, unavoidable factors can make it difficult to adhere to a particular policy (McDonald 1996).

If the cord is not clamped, the umbilical circulation ceases when the umbilical arteries close and the cord stops pulsating. Delaying clamping allows time for a transfer of the fetal blood in the placenta to the infant at the time of birth; placental transfusion. This transfusion can provide the infant with an additional 30% more blood volume and up to 60% more red blood cells (Mercer 2001). The amount of blood returned to the infant depends on when the cord is clamped and at what level the infant is held (above or below the mother's abdomen) prior to clamping (Yao 1974).

The suggested neonatal benefits associated with this increased placental transfusion with delayed cord clamping include higher haematocrit and haemoglobin levels (Prendiville 1989), additional iron stores and less anaemia later in infancy (WHO 1998a); higher red blood cell flow to vital organs, better cardiopulmonary adaptation, and increased duration of early breastfeeding (Mercer 2001).

Arguments against early cord clamping include the reduction in the amount of placental transfusion and in the associated benefits of this extra blood volume. However, these differences in placental transfusion associated with early and late cord clamping diminish quickly over time, becoming negligible at three months of age (WHO 1998a). Early cord clamping may increase the likelihood of fetomaternal transfusion (the amount of blood that is forced back across the placental barrier into the maternal circulation), as a larger volume of blood remains in the placenta (McDonald in press). Because of this, early cord clamping should be avoided in rhesus negative women (Prendiville 1989). Early clamping has also been associated with higher risk for the pre‐term infant in developing respiratory distress syndrome (Rabe 2002).

It has also been argued that the increased placental transfusion can be a disadvantage, causing an excess of red blood cells (polycythemia, Mercer 2001; Gupta 2002) and/or an abnormal increase in the volume of circulating fluid in the body (Gupta 2002; Saigal 1977). There is some concern that such increases in blood volume and the amount of red blood cells could result in overload of the heart and respiratory difficulties. However, there is also evidence that the newborn is capable of rapid adjustment to these increases (WHO 1998a). Delayed cord clamping has also been linked to an increase in the incidence of jaundice (Prendiville 1989). Such arguments support the early clamping of the umbilical cord. In addition, early cord clamping has been associated with a reduction in the length of the third stage of labour (Prendiville 1989). One of the aims of active management is to reduce the length of the third stage because the longer the placenta remains undelivered, the greater is the likelihood of maternal bleeding (Inch 1985). However, the available evidence does not reveal an effect of timing of cord clamping on blood loss or postpartum haemorrhage (Prendiville 1989; McDonald 1996). Evidence so far suggests that the key element of the preventative approach to third stage management appears to lie in the administration of an oxytocic drug. A delay in time before clamping the umbilical cord may be less crucial as the cord ceases pulsation within the first two minutes of birth in the majority of cases (McDonald in press).

Evidence remains unclear as to whether one timing of cord clamping policy is more preferable to another. This review seeks to address this issue further. Since evidence suggests that the effects of early versus late cord clamping may differ in pre‐term and term infants, these are the subjects of separate reviews (see Rabe 2002 for a review of delayed cord clamping in pre‐term infants). The following review will concentrate on the effect of early versus late cord clamping on the incidence of postpartum haemorrhage and other maternal and neonatal outcomes.