How should I go about telling my parents this?

My parents don't know that my wife and I were drunk when we had and when she got pregnant with our son. It was the night of my nineteenth birthday, and my friend had alcohol there, and we got a little out of hand, got drunk, and had . I'm beginning to think that it's time that they know this. However, I don't know what they'll say or think about me and my wife, because they were always preaching to me about how I shouldn't drink when I'm not twenty-one. Do you have any suggestions for telling my parents about this? Thanks