A surrogate mother is read as carrying something for someone else. Dream books link it to generosity, and to holding a responsibility or a hope that will not stay with you.
When this appeared in your dream, what were you feeling?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.