She imply not wanting to end up in the same situation as her mom many time
In the story & saying “tried so hard” in this chapter doesn’t really add up. If she thought she couldn’t get pregnant but was still taking risks, then her chances were never zero.
And with a family history like that, her risk of complications is already higher. So it’s not that she was being careful per say. N i’m not blaming her alone, just an observation here.
When she said she tried hard, she was referring to being useful. It wasn't about producing an heir. When she first arrived at Riftan's Castle she said that she has to be useful because she wouldn't be able to produce an heir. She knows that in that world, if women can't produce an heir, than they are useless. She didn't believe that she could get pregnant which is why she was so obsessed with being useful in other ways. She even stated at one point that she hopes he never finds out about her inability to get pregnant.

I tried so hard to not have a miscarriage ” hmmm questionable if war is a good preggo spa location back then knowing your body n all. Also Riftan should have remind her that he is likely not impotent lol and she might get it out of the hundred times they f around