By the time we entered the swing scene, the wife part of our duo already had had a tubal ligation, so it was a moot point. The male side is still fertile and we discussed what happens if a female play friend got pregnant. We were on the same page that we'd do whatever we could to support her decision, though, fortunately, none of the women we've been involved with had an unplanned pregnancy. Though a hypothetical for us, if wifey got pregnant during play, we'd raise the the baby like the rest as all life is beautiful and precious.
As to those with a kink for pregnancy, no judgement, as everyone has to find their own way. Anyone considering that, however, really needs to be sure everyone is on board with the idea and is prepared for the ramifications. Parenthood is a lifelong commitment that requires a lot of time, financial resources, emotional impact, changed life course, et al. Put another way, a hot breeding session may sound like a delight, but changing poopy diapers at 2:00 AM is a lot less so.
At the end of the day, everyone has to figure out what works for them, what risk they're willing to take, and how to respond to the unexpected. Cheers.