I don?t use synto routinely for homebirths. When working at a hospital I always give the woman the option not to have the synto.
I believe that giving synto as the baby is being born is like taking some panadol at bedtime just in case you are going to have a headache in the morning.
Synto acts by causing the uterus to contract and thus helping to stop excessive bleeding and expelling the placenta.
The down side is that it will also cause the cervix to close and there is a chance of trapping the placenta inside the uterus.
Also the majority of women do not bleed excessively after birth. Synto, once injected works very quickly so why not give it if a woman starts to bleed excessively and not because there is a chance that she might.