Throughout my engagement, people joked about how I'd lucked out in the mother-in-law department because my husband's mother was extremely chill and not obsessed with the idea of grandkids. My husband and I are dedicated to being child-free (he got the snip in college), and it was a relief to us both that his mother was fine with that. I never expected that the problem would be with my (younger) sisters-in-law!
A wily trial lawyer I once worked for delighted in asking outrageous personal questions, and people almost always answered him. "Never forget," he told me, "a question asked is not necessarily a question you have to answer." That got me thinking. When I was feeling tender, defensive, or vulnerable, I wasn't ready to explain my situation. Then I decided I had every right to skirt the subject, because my reproductive status was no one's business but my own.
If it's your job to figure out when to share this, it's also a partner's job to figure out when to ask. Wanting kids isn't like monogamy or working for a living, where until instructed otherwise people can basically assume that's your plan. More people than ever are deciding they don't want kids. The fact that you're one of them is not shocking, confronting or even especially unusual.