Whether or not it’s possible, which it certainly is, you need to address the issue of why you’re suspicious and what to do about it. Pregnancy won’t stop a cheater from cheating.
FWIW my husband and I have lots of friends of the opposite sex. Al above board, no OTT amounts of contact, no texting into the night and going all giddy. Plus, these are friends we’ve each had for years before we even met, so less suspicious altogether.
My own anecdote of pregnancy cheaters. I know of quite a few, but the ones that stick out:
Someone I knew years ago, found out about the OW when she was in the hospital giving birth, because the other one was giving birth at exactly the same time. Turns out that SHE was actually the OW, and the other woman was the wife of about 15 years!
Another one that sticks in my memory was an old friend who after giving birth, the baby had to have an operation and was really poorly. The husband said his boss had refused him time off for the operation. When the wife called his work to plead with the boss, she explained to the secretary the situation. The sec said something like “oh but I thought you’d only just gone into labour, he’s at the hospital now isn’t he?” The first baby was about a week old at this stage. Then she gets through to the boss who says the husband hadn’t asked for time off for an operation and also wasn’t she in labour right now? She says no, says her name, and he says oh aren’t you divorced? No. Anyway, turns out he was seeing a client that the company works with for years, had told everyone he was divorced and that OW seemingly was fine with him never staying over or living together and supposedly never suspected, despite him fully living with his wife the whole time and never disappearing off, that he may not actually be divorced. Obviously it all blew up and now he doesn’t bother seeing any of his kids or pay anything towards them. This is a man who cried with happiness on his wedding day, brought home flowers for his wife every Friday, bla bla bla.