how to tell people of unplanned pregnancy

So, I have 14month twins and we werent going to have another baby for 2.5 more years. Financially it made sense, twins is a lot of work, so that made sense, i am 32 years old and have told people we just cant have another baby, especially financially. We are also struggling on our marriage a little. How do you tell people that you got pregnant when you didnt have a period and still ovulated? I dont plan on telling people until Christmas.