I am creating a setting in which biomancy can be used to make childbearing easier on the mother. Biomancy is a form of magic that allows for the manipulation of certain biological processes. Midwives take the form of witches who specialize in childbirth-focused Biomancy magic. Some ways it can be used are as follows:

Widening the birth canal to make passage easier.
Reducing hemorrhaging and repairing tear.
Lessening pain from cramps and labour.

Another way I wanted was to speed up rate of gestation from the traditional 9 months by using runes. These runes are cast using an incantation and speed up the body's natural proccess to a limited extent. They are not permanent and must be recast every so often.

There is a particular trope called Express Delivery that talks about this very thing, but many examples come off as crazy or unrealistic because they don't take important things into account, and they just seem to work without any cost or adverse effects. The human body is capable of impressive acts, but such processes take a lot of time, and can take a toll on the body. There are hormonal and physical changes that the mother must go through. Nutrients that the child is made of must also be pulled from the mother for it to develop fully.

The question is: how fast can the body safely adapt to these conditions without causing problems for mother and child? What can one do to alleviate these risks?