When your lady tells you that shes pregnant, do not abruptly deny the pregnancy. Its wrong and disrespectful to both her and the issue. Advice from the house is that you man up an accept responsibility of your action.
Silence is the worst. It leaves a woman regretting everything she ever did with you. Try not to be that way. You are superior to that.
There are many things you can say even if you don’t mean them. One such example is “Wow! I am so happy babe.” Simple.