Follow-up to earlier ask: All the signs Sherlock deduces about Mary being pregnant in TSoT could have been things Mary is intentionally doing to give him fodder for a pregnancy deduction. (Not liking the wine any longer, heightened appetite, etc.) Mary knows John would behave protectively toward the mother of his child, even more than a wife, especially once he knows she is an assassin. Pregnancy keeps John focused on her. She “will never let that” (losing John) “happen”, after all.
Anything’s possible, I guess. But if John was going with her to ultrasounds and stuff (not that we know whether he was), that would’ve taken a hell of a lot of effort.
But I think Mary ceased to get a pass from Sherlock’s deductive faculties after he discovered she was lying to John. Mind you, he was in the hospital for quite a long time, according to his mum at Christmas (I asked a trauma nurse, who said that she’d expect them to keep Sherlock in the hospital for at least a month after a wound like that; gunshots, especially gut wounds, are susceptible to complications from infection). So unless she came to visit him, he might not have laid eyes on Mary again until Christmas.
If she were lying about the pregnancy, I’m not sure whether that’d be less emotionally damaging for John or not. The entire existence of the wife he thought he knew turned out to be a lie, and then he took her back and gave her a shot at being his wife as the person she wants to be. And then if she was lying about the pregnancy… I suppose it’d be less traumatic for him than actually having a kid and then having something happen to it, but I honestly have no idea how a person would even react to that, beyond the initial scream of rage.
And it’s a lie that, by its very nature, has an expiration date. By the end of the season, she’s at least late in her second trimester. I think a miscarriage at that stage would require an entire jump-off-a-roof-style plot to fake realistically.
So, I mean… It’s a show where that jump-off-a-roof plot did happen, so like I said, anything is possible.