BAL, We never hid pregnancies, we more so kept it to ourselves until we got used to the idea. With DD1 she was a major surprise and we took a little bit of time to get our head round the idea of being parents when being parents was never on the cards for us (Dh and I started our relationship o with both of us never wanting children, or even marriage, but now we have both and wouldnt want it any other way). With DD2 we were essentially homeless in that we were moving towns, had given notice on our current house and whilst moing out the house the real estate had said we could have changed and we were left staying at DH's parents house.
DD3 on the other hand, I was in denial for a long time beore I took the hpt. People were telling me that I was complaining about pregnancy symptoms, and I reused to believe so would blow it of.

So for us it wasnt about hiding the pregnancies, but more so giving ourselves the time to celebrate privately, get our heads round the idea of little munchkins running around, and working out the perfect way to tell people.