We've seen stories that run a whole spectrum,.Hostage. Given that unprotected sex falls under "risky behaviors," for many it is just chance that they might not get pregnant.
For others in longer relationships, it may be a way of keeping a SO attached,.since BPD is an attachment disorder, after all, and having a child may be a way of keeping the father around (the large number of single mothers notwithstanding). Some of us mistakenly thought similarly, thinking giving her what she wanted (a child), would make things better. This is our own ignorance or immaturity.
In my case, it was both. She had a lot of unprotected sex with a younger guy who eventually cheated on and left her. She still idealized him, and did the same when he came back for a time to use her sexually (I would say it was mutual, but unlike him, she still wanted to marry him).
There was a brief guy, likely NPD, with whom she wasn't in love, but she didn't use protection. Neither of these relationships yielded a child. With the NPD, I think she just wanted a child.
Enter me about a year later. After "friend dating" for a few months, it went from the first kiss to the bedroom, in like 5 mins. My lousy boundaries. She wouldn't have used protection. A week later, she asked me, what would you do if you got me pregnant? I dint specifically recall my answer, but she didn't like it. I may have said something like, "I took precautions for that to not happen." Invalidating to her, though correct.
A year later, after one recycle where she broke up with me, I think she decided that I was the stable, mature guy she wanted to have kids with. She got pregnant with S5 right away (so much for those other younger guys
I made the same mistake with D2, giving her what she wanted when my logical mind was screaming, "don't!" Now she's cycled back to another younger, narcissistic type guy. But she fixed herself to never have kids, so in this sense, I will always be The One. I think part of it (and I certainly volunteered, being 10 years older), was that on a level she may have realized the stress of pregnancy and infantcy contributed to the downfall of our r/s. Of course it did.
Speaking in general, I don't like it when guys say a woman (BPD or not) uses a kid to "trap" them. Sex is a r/s between two people (or more if that's one's proclivity). Each partner, short of rape, has a choice in the matter.
hurting300, my Ex is now with whom I call "The Three." I was "The Two." Averaging in our 6 year r/s, that means there is a new "The One," about every 3 years. I know after S5 she finally thought I was The One. I found a note about it on my computer after she left and I was going through old files.