Yeah, from a medieval/renaissance time period perspective, allowing women in the military isn't particularly wise - hence why it was nearly never done.
If your army has pretty much zero force multipliers, you just need large numbers of people to fight, hence you want as big of a population as necessary. If you have 1 in 4 children dying in childbirth (and a mother 1 in 100), you kinda need to make sure that you have women around to procreate and not fighting in wars and dying/being injured. Also, many women of young to middle age were pretty much CONSTANTLY pregnant during their life times, with a year or two apart at max making them not particularly effective soldiers.
I can imagine cultural/religious reasons allowing it/enforcing it, but for even basic time period accuracy it seems a bit odd for it to be a 50% chance. My main issue though is just that you'll be ending up with around 30% of civilisations having a woman leader with women fighting and men not. Again, whilst I realise it's not looking for historical accuracy, it's biologically not sensible.
Note that in URR's earliest posts there was stuff like Minotaur generals of armies and the acceptable number of squares for a dragon to take up being casually discussed. Even if it doesn't look that way, we are in the realm of high fantasy. I'd say it's acceptable to say childbirth isn't usually fatal in fantasyland.