I posted a blog entry about this, but I'll mention it here, too, since I can add this to various topics/articles, which will make it more likely to be seen.
I did a lot of research into parenting communities wherein people use a surrogate or egg donor, and the terms the parents and the children most prefer to use are "genetic donor" and "genetic mother".
Many parents still call their child their biological or "birth" child; some of which admitted to feeling inadequate while they called their egg donor the biological or "real" mother. The majority of the parents whose stories, experiences, opinions, etc. I read stressed that they are not the child's "adoptive" anything, because they did have the child—they child is their own.
Because it is such a controversial topic and can cause a lot of hurt, please do not call Lori Stevens the twins' "real" or "biological" mother in the main articles. You are free to have your own opinion in non-series pages (e.g. your blog posts, comments, and forum posts), however.
Elizabeth Wilson is Carter and Taylor's birth mother; David Wilson is their biological father; Lori Stevens is the twins' genetic mother and the Wilsons' genetic donor.