@Pecan_nutjob
When I get out the bag it's because I want something to really make me poo because I've not gone in more than three or four days, and perhaps even longer. This doesn't happen often, but it does happen.
On other occasions, if I've missed my daily poo and just need a ‘little help’, rather than straining to poo on the toilet, I use an adult bulb rectal syringe to squeeze in one or two bulb fulls, then sit and wait a few minute. If I'm not badly constipated, an easy poo soon follows.
But, if a bag enema is required, I fill a bag with warm water with just a swish of Ivory bar soap. Too much soap and one starts to camp strongly well before the bag is empty. While some may enjoy those feelings, premature urges tend to reduce the full effectiveness of an enema, IMO.
For me, the best enema is comfortably warm… just a bit above body temperature… and mildly soapy. It doesn't take a lot of soap to get strong bowel contractions after a few minutes. The enema should be given slowly with the bag hung about two feet above you anus. Hanging the bag low allows the flow to stop if the recipient gets a cramp. Given as described, it takes five to ten minutes to get the full bag in and there is little urge to poo for another few minutes. But then, the urge becomes rapidly intense and everything comes in an unstoppable rush.
As for the enema in Call the Midwife I suspect the intended purpose of the enema was more to cause strong cramping, hence starting or speeding up labor, than to make the woman poo. Traditionally, 3H enemas… High, Hot, and a Hell of a lot… have been given for this purpose.