5.5 Timing of Cord Clamping

The umbilical cord can be clamped immediately after birth or at a later moment, and this may have effects on the mother and the infant (Prendiville and Elbourne 1989). The effects on the mother have been studied in some trials (Dunn et al 1966, Botha 1968, Nelson et al 1980). There was no evidence of a significant effect of the timing of cord clamping on the incidence of postpartum haemorrhage or on feto-maternal transfusion. The effects on the newborn have been studied by observational studies and randomized trials.

There are a number of observations on the effects of the timing of cord clamping on the neonate (Buckels and Usher 1965, Spears et al 1966, Yao et al 1971, Nelson et al 1980). If after birth the infant is placed at the level of the vulva or below that level for three minutes before clamping the cord, this results in a shift of about 80 ml of blood from the placenta to the infant (Yao et al 1971, 1974, Dunn 1985). The erythrocytes in this volume of blood will soon be destroyed by haemolysis, but this provides about 50 mg of iron to the infant’s reserve and reduces the frequency of iron-deficiency anaemia later in infancy (Michaelsen et al 1995, Pisacane 1996). Theoretically this transfusion of blood from the placenta to the infant might cause hypervolaemia, polycythemia and hyperviscosity, and also hyperbilirubinaemia. These effects have been studied in a number of trials (Prendiville and Elbourne 1989). Babies born after early cord clamping have lower haemoglobin values and haematocrits. With respect to neonatal respiratory disturbances there were no significant differences between the two management practices. Neonatal bilirubin levels were lower after early cord clamping, but no clinically relevant differences between the two practices were noticed, and no differences in neonatal morbidity.

Late clamping (or not clamping at all) is the physiological way of treating the cord, and early clamping is an intervention that needs justification. The “transfusion” of blood from the placenta to the infant, if the cord is clamped late, is physiological, and adverse effects of this transfusion are improbable, at least in normal cases. After an abnormal pregnancy or labour, for instance in rhesus sensitization or preterm birth, late clamping may cause complications, but in normal birth there should be a valid reason to interfere with the natural procedure.

If controlled cord traction after oxytocin administration is practised, as is the case in many obstetric departments worldwide, early or relatively early clamping of the cord is mandatory. However, where late clamping is taught and practised, i.e. after the pulsations of the cord have ceased, usually after about 3-4 minutes, adverse effects have not been recorded. In addition, recent research supports late clamping, because it may prevent iron deficiency anaemia in childhood, which might be of special importance in developing countries (Michaelsen et al 1995, Pisacane 1996). Although at present there is insufficient evidence on which to decide between early and late clamping, this issue clearly deserves more attention.