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What is fetal distress?
Even in the medical fraternity, there is no firm agreement as to what this term means, despite its common use.
In essence, it refers to a state of the fetus brought about by insufficient oxygen reaching the fetus. If oxygen deficiency is severe and prolonged, permanent damage to the baby could result. This is why any hint of possible fetal distress is taken seriously.
What are the causes of fetal distress?
There are several potential causes.
Fetal distress is commoner during active labour but could occur before labour onset. This is uncommon.
Placental abruption, which is a condition where the placenta. (afterbirth) detaches from its base partially or wholly, is one of the more common causes of pre-labour fetal distress.
Vigorous fetal activity sometimes leads to a cord accident, which may be in the form of a knot or entanglement of the cord around a limb. This could lead to partial occlusion of the vessels in the cord, leading to distress.
Other causes of distress before labour onset remain obscure, even after the baby is delivered.
What about causes of fetal distress during labour?
Any activity that reduces the blood supply to the fetus will cause fetal distress.
If the cord is compressed, either as a result of being around a fetal limb, neck, trunk or simply by being compressed by the fetal head against the pelvic side-wall, features of fetal distress will follow. Correction to this can occur spontaneously as a result of fetal movement or the cord sliding away from the pressure point, hence relieving the compression. Sometimes this does not occur and a rescue procedure needs to be carried out.
Is hyper-stimulation of the uterus a cause of fetal distress?
Yes. This can occur spontaneously or following the infusion of oxytocin. If the uterus contracts strongly, with the contractions being prolonged and coming close together, this will reduce the amount of blood (and therefore oxygen) that is getting to the placenta and ultimately to the baby.
If this state of affairs is sustained over several minutes, fetal distress will ensue.
Can hyper-stimulation be overcome or reversed?
Yes. This is overcome quite easily simply by stopping the oxytocin infusion, if this was the cause.
If it occurs spontaneously, an intravenous injection of a tocolytic drug can be given and this will very quickly eliminate the over-stimulation. These drugs are also available in an inhalational (aerosol) form but this method is associated with a slight delay in action.
Tocolytic drugs simply relax the muscles of the womb to negate the effect of sustained strong contractions.
Can the placenta detach in labour before delivery?
This can happen but is a very unusual occurrence.
It will cause fetal distress, the gravity of which will depend on the extent of placental separation. It could lead to a caesarean section unless labour is in the second stage, when instrumental vaginal delivery may be the quicker and preferred option.