The comment that delayed clamping can lead to blood flowing back through the placenta in incorrect - physiological third stages are usually conducted in a squating/upright position (ideally the best position for labour and birth) and therefore gravity would prevent the blood from flowing upwards from babe to placenta. If this position is used it usually takes very little effort or time for the placenta to be expelled.

Physiological third stage is the recommended option when labour and birth have gone smoothly as it doesn't interfere with your natural hormones. Whilst there is a little more blood loss duirng the 3rd stage it is not normally dramatic enough to make a difference and if it does become dramatic then you can revert to active management.

Whilst active management may prevent some blood loss during the 3rd stage it can actually result in a heavier and longer lochia (the period type loss for days after birth) so either way the blood is lost.

Babies also benefit from the delayed clamping as they are meant to receive that influx of blood from the placenta and denying it through early clamping can lead to anaemia.