Usually it seems that the motive for asking is 1) to validate their own reproductive choices or 2)being nosy. Thus the answer to the person asking because they are taking a very long, public and un-scientific poll is "none of your business." And the answer to the person asking because they are being nosy is "none of your business."
My children are small and they are both at difficult stages of life. My life and routines change to adapt to their needs and currently I am not ready for another baby. However, I don't know how I will feel in a year or two. I am not going to share my very personal decisions with the public any longer. We love our children and believe that they are a blessing. That's my public statement on this topic. End of discussion!