Active management of the third stage is a very interesting subject. Ergometrine originally was used to control haemorrhage after the palcenta was delivered. Then doctors decided that since it was good for that, then lets give it to speed up the delivery of the placenta. As drugs were developed through time, syntocinon was developed and the drug syntometrine was used routinely for the delivery of placenta. The theory was that if the third stage was shortened then haemorrhage was prevented. That statement is not entirly true.
In a totally physiological labour, the placenta will deliver on it's own. There is usually a greater blood loss at delivery but less in the following postnatal days. In active management there is less blood loss at delivery but there is much more in the days following as the uterus relaxes as the drug wears off. Many women have had the experience of going to the toilet and feeling a flood of blood pour out in the first few hours after birth.
Where a labour has been interfered with by using opiate pain killers, epidurals, induction - the third stage should be actively managed because the natural flow of labour has been interfered with. It is possible to wait and see what happens post delivery. If bleeding starts, the injection could then be given and the placenta delivered.
The ergometrine component can lead to retained placenta. Syntocinon on it's own is used in may units. The problem is that it is unlicensed by the drug company for intramuscular use (IM). It was originally designed for intravenous use. However, it has been used safely and effectively for many years. The drug companies will not finace a costly trial to find out what is already known. As it is unlicensed it requires to be prescribed in law by a doctor. This is a problem legally for midwives where the hospital pharmacist will not allow midwives to administer it on their own authority. Midwives can do that already with a number of other drugs.
I believe where possible women should have physiological third stage (physiological labour). If it needs to be managed the syntocinon is my preferred drug. I have seen too many women have the first minutes with their baby ruined by vomiting - a side effect of ergometrine.
this is a good article explaining it all