Almost sound like Giving Back by sarhea (Rated MA.) Although she gives birth in a hot tub rather than a hot spring
Kagome insists on taking a small break in the shard hunting quest, to volunteer for a specific charity in October. In the future she meets someone from the past, learns of things she had never expected, and finds a place for herself. [Nominated 2012 Q1 Dokuga Awards: Best Canon and Best Lemon] Warning: discussion of breast cancer, explicit sex, Kinks, Exhibitionism, BDSM, beastility (closest warning word), Pregnancy, Labour ~ For the 'Think Pink' Challenge ~ For r0o’s 3rd GM Challenge 2011.
www.dokuga.com/fanfiction/story/6654/1
It could also be Somewhat Happy Endings by midori Haru on FFN (M there MA here)
When Kagome made her strange request, Sesshoumaru had thought she was mad. But then he looked a little closer and realized, her mad request was the only thing likely to keep her sane in a situation vastly worse than the one she'd suffered during the hunt for Naraku's death. Neglect, it seems, can kill a person slowly.
www.fanfiction.net/s/9565648/1/Somewhat-Happy-Endings