My water broke at 12.5 weeks. Anyone else??

Last week I was on vacation with my husband. We were having a relaxing morning in a cabin we rented in the mountains. I was lying on the sofa. No pain, no bleeding up to this point. I stood up and felt a tiny pop. Again, no pain. But I realized that water was trickling down my leg. I called my doctor right away. They asked the standard questions. But when I said there was no bleeding or cramps they told me I'd be fine. 20 minutes later I ran to the bathroom when I felt a rush of liquid coming out of me. When I whipped the liquid away, there was my baby. I have no idea why or how this could happen. I meet with my I obgyn next week. Has this happened to anyone else???