To tell woman about her partner's kinks?

[frogmella123]

She is a distant acquaintance, I know him better. They had a brief relationship (him on the rebound) and she is now pregnant.
So they got "together", not living together or even in the same county, but in some sort of situationship.
But I know he is into swinging and sex clubs. She doesn't know. He hasn't told her.
I know it's really not any of my business and I should probably leave it well alone. I don't really want to get involved, except I can't shake the feeling that if it were me or were happening to a close friend then i'd want to know. She is basing a relationship and that of their unborn child on lies. She thinks he's faithful and monogamous.
I don't judge him for how he wants to live his life or get his kicks, but i do judge him for leading this woman up the garden path.
AIBU to say something?

YABU = Stay out of it
YANBU = She deserves to know

@FallOfTheHouseOfUtterlyButterly maybe read what the OP has written?

How do you know she isn't into that herself? Why do you think you know him better than the person he chose to have a child with?
They're not even together anymore as far as I can gather so surely there's little need to get involved? Unless you have actually attended sex clubs and swinging sessions with him, how can you be so certain about what he may or may not get up to there, or anywhere else?
So no. Don't say anything. You'll look foolish.

Gosh, people are hard of reading.

He has told OP-
the woman isn't aware he swings.
the woman thinks she’s in a monogamous relationship having got accidentally pregnant.

Her consent is based on that.

In fact she’s exposing herself and her baby to every other partner he goes with.

If I found out he was risking mine and my baby’s health like that, and no one bothered to tell me, I’d be gutted.

🙄 handmaid alert.

Aren't all of the 'none of your business people' the hand wringers when something appalling happens? 'But why didn't someone DO something?' brigade.

She's said the swinging is active and the pregnant partner (whatever the exact status) is unaware.

I'm not being rude but haven't you read any of the OP's posts? It's not about him enjoying swinging in principle. It's about the fact he's having recreational sex without her knowledge. Doesn't matter that it's part of a group.

Point being, if she isn't aware, she probably hasn't set any rules or boundaries. That isn't how swinging or relationships work surely?

Quote: “If he is being unfaithful then of course she has a right to know.“

Quote: I did not read that he is a cheat.

Quote:

Maybe I am reading it differently but I did not read that he is a cheat.

If he is being unfaithful then of course she has a right to know.“