It should only be allowed if they are in private rooms. Would be even more hellish than a post natal ward already is. There is to me the obvious issue of some women having a phobia of strange men which I know some people have countered.
BUT if you forget the above point then you have:
12 adults in a space meant for 6, the wards cam be cramped enough as it is so makes it feel more claustrophobic and more difficult from a moving and handling point of view for staff to do what they need to do.
12 people using a toilet designed for the use of 6 increasing the wait for the toilet and making it more difficult to keep hygienically clean.
12 people using the shower designed to be used by 6 increasing g the wait for a shower, making it more difficult to keep hygienically clean and since the shower is often in the same room as the toilet increasing the wait for the toilet too.
It is hard enough to sleep in a ward due to the unavoidable noise, double the number of adults would only increase the noise ( even if they were all reasonable and tried their best to be quiet)
More people on the ward at night impacts on fire safety and by letting more people stay overnight the staff would become legally responsible for ensuring their health and safety taking them away from patient care.