Abstract
The authors hypothesize that particularly severely compromised and asphyctic term
infants in need of resuscitation may benefit from delayed umbilical cord clamping
(after several minutes).
Although evidence is sparse, the underlying pathophysiological mechanisms support
this assumption. For this review the authors have analyzed the available research.
Based on these data they
conclude that it may be unfavorable to immediately clamp the cord of asphyctic
newborns (e.g., after shoulder dystocia) although recommended in current guidelines
to provide quick
neonatological support. Compression of the umbilical cord or thorax obstructs
venous flow to the fetus more than arterial flow to the placenta. The fetus is consequently
cut off from a
supply of oxygenated, venous blood. This may cause not only hypoxemia and consecutive
hypoxia during delivery but possibly also hypovolemia. Immediate cord clamping may
aggravate the
situation of the already compromised newborn, particularly if the cord is cut
before the lungs are ventilated. By contrast, delayed cord clamping leads to fetoplacental
transfusion of
oxygenated venous blood, which may buffer an existing acidosis. Furthermore,
it may enhance blood volume by up to 20%, leading to higher levels of various blood
components, such as red and
white blood cells, thrombocytes, mesenchymal stem cells, immunoglobulins, and
iron. In addition, the resulting increase in pulmonary perfusion may compensate for
an existing hypoxemia or
hypoxia. Early cord clamping before lung perfusion reduces the preload of the
left ventricle and hinders the establishment of sufficient circulation. Animal models
and clinical trials
support this opinion. The authors raise the question whether it would be better
to resuscitate compromised newborns with intact umbilical cords. Obstetric and neonatal
teams need to work
even closer together to improve neonatal outcomes.
Key words
delayed umbilical cord clamping - asphyxia - resuscitation - neonatal hypoxemia -
neonatal hypoxia
