Hey! What if she miscarried because of the damage done to her body by being Insect Queen?
Wow, that's an interesting point - and may account for why she put the ring away: it damaged her body.
The alien Lana saved to obtain the bio-ring was insectoid in nature; it is conceiveable that it probably didn't know about mammalian biology enough to say what would happen if it was to be used by a mammal.
The female reproductive system is much more vulnerable to damage, because a woman is born with all the eggs she will ever have, whereas men make new sperm cells all the time. Insects however, do not give live birth, and lay eggs. It's possible the mix-n-match aspects of the ring had long-term effects.