What are your toughts on Aemma's theory

I saw once a theory stating that Aemma's last pregnancy was sabotaged by Otto. But I never saw people actually debating on it.

The theory is based on several arguments: One meta saying that in asoiaf universe, death are rarely natural. So we should investigate whether this death could profit to anyone.

And it is clear that Aemma's death profit to Otto so he can set Alicent as queen

Then, does the show give us any hint that Otto could have so this? In the first episode, when Aemma start to have problem, the maester go tell otto before Viserys. Maesters have the skills required to sabotage a pregnancy, and have access to the queen, so it is plausible that Otto could have used this way to poison the queen in order to make the pregnancy fail.

From my point of view, this is possible, but I don't see any other hint from the show to validate this theory. Do you think Otto could go that far? He has been hand of two kings, during peaceful times, so he has been chosen as a trustworthy person.

Was it something planned from a long time?

Or Aemma's death was just an opportunity that Otto took? In that case do you think he has other plans to put Alicent (and thus himself) in a position of power before Aemma's death?