Agree that it depends on your relationship and agree that you should emphasize the "just between us" aspect if you tell. I told my mother, who I thought would be very supportive, but she then told all of her friends without asking and didn't really offer a lot of support. Then, we were peppered with a number of really insensitive questions from her friends about frozen embryos, "killing little babies," etc. That said, I told my father, who I feared would be awful about it, and he was a prince.