Pregnancy is one of those things that we talked about a lot before becoming involved with other people. For mostly financial reasons we have all the children we want. If it were to happen though I would work on building a stronger relationship with my metamour. The child to be would be a part of our family and therefore by default so would my metamour. I would want the children to all grow up together and to know each other. I'd really really prefer that it never happen though and I know that I never want to be pregnant again (and will take all precautions to prevent it).
Everything will be ok in the end. If it's not ok it's not the end.