I am not in a poly relationship but if you all live together and are both wives to the husband, aren't you both "mothers" to all of the children? If that is so, then you will be a mother to this child too. As the mother of 2 girls, both of whom didn't grow in my body, I couldn't love them anymore than if they grew in it. One is by traditional surrogacy and one by adoption. Both girls have bonded with me as their new mother and I to them. If you are to share a house and husband, it seems OK for you to share this baby too. So, maybe you can think of it as a surrogacy arraingment, where you are one of the parents meant for this little one...go shopping, Drs visits, feel it kick etc. Also you need to grieve your own "loss of not getting pregnant" in your body. Even today I still wish I could experience a baby growing in me, birthing a child etc, but with a hysterectomy, that isn't possible.
Melissa, L&D RN now...aspiring midwife-2-B,
20yo DS, 7yo DD, almost 2 yo DD, 1yo GDD