Yeah, we got one point out of the way.
Now, I'm focusing on the other point. If somehow the Lady mantle is allowed to take a pregnant Lady (not considered mother yet) I don't think the mantle would take action against the fetus as that would probably violate the prohibition regarding the Queens not killing mortals. I see the defense mechanism depicted in Molly's encounter with Ramirez as the first defense mechanism we've seen. If somehow it gets bypassed, and the mantle isn't destroyed by the Lady becoming just short of a operative definition of 'mother', then I think the pregnancy would get inside the mantles defenses such that it couldn't touch it. The mantle would then push the Lady toward becoming Queen at all costs. It wins either way by having the Lady vacate its mantle. Lady dies in attempt, Lady mantle passes. Lady becomes Queen, Lady mantle passes. Each of which would need to occur before 'birth' if that is the definition of 'mother.' This is entirely mute however if conception is considered adequate by the mantle to be a 'mother.' This then would allow for possible sex between the Lady and another with the exception that if such a conception occurred as a result, fulfilling the 'mother' definition, this would then destroy the Lady mantle.
In short, I'd argue the mantle could not cause a miscarriage. This circumstance, if it hadn't already caused the Lady mantle's destruction, would be inside the mantles defenses and prohibited by law that prevents the Queens from killing mortals.
Now, the question becomes if on the off chance this may be accurate, would it be at all relevant. That answer at this point is a probable no. It, in my theories, mainly applies to Murphy and on the chance she TT's into the past pregnant with say Harry's child, who may be Marcone. All of these Wag's are increasingly unlikely when combined together. They also require a more complex storyline to back them.