Liandra can't get pregnant until the quest "Trouble At The Well" is complete (requires learning the Summon spell). Normal chances once that is done but apparently only standing sex can knock her up. Use EFP (or scumsave) if you want to ensure she's pregnant.I always but she's not pregnant yet
She doesn't give birth until the quest "A Home In The Woods" is started (requires completing the quest "Let There Be Light" and pregnant 19+ days).