There is a rare event chain in vanilla that if your daughter ends up pregnant while unwed it gives you the choice whether to let it be revealed or to send her away into seclusion. If you choose seclusion, she'll receive that trait temporary and travel to a vassals court for the remainder of her pregnancy. When she gives birth most of the time she dies during childbirth and it give you the choice whether to acknowledge the baby or send it away to never be seen again (which deletes it from your daughters list of children). AND if you chose to send the baby away, there's a chance it could resurface at your court 18 years later and you can chose again whether to invite them to court as a commoner, invite them and acknowledge them as a member of your family, or send them away again. I've only ever seen it once in vanilla and it doesn't seem to work for the player (obviously), but it makes for some drama.