Like @giveitago we decided to tell the people we would tell anyway if it all went wrong. For us that was immediate family and one or two close friends. They knew from 5 weeks.
My bosses at work also knew then. We'd been doing IVF and they knew where we were up to with that and that we had had our embryo transfer, so it felt a bit weird not to tell them the result. The rest of our family and friends we told after our Harmony test was clear and we'd had our NT scan at 12.5 weeks