I’m not sure what that has to do with fanfiction but yes, I do believe you can write about stories with pregnancy.
If you’re unsure, you can submit a ticket asking: https://episodesupport.zendesk.com/hc/en-us/requests/new?ticket_form_id=114094007673
Also Episode will be going in depth and explaining stuff in more detail, this post will be of interest to you: We're Expanding Episode Explained!