debating on whether or not to tell my mom

RussianMommy

my mom and i are close, but i literally just found out over the past few days that im pregnant (god that sounds so weird to say)... 

she is in town for a week, and it's her birthday. so i can either "surprise" her with a "happy birthday grandma" card or wait to tell her, but it wont be able to be in person since she lives far away. she leaves aug 10th

should i just wait or tell her?