The father's pain

A married couple went to the hospital to have their first baby delivered.
Upon their arrival, the doctor said he had invented a new machine that would transfer a portion of the mother's labour pain to the father.
He asked if they were willing to try it out. They were both very much in favour of it.
The doctor set the pain transfer to 10% for starters, explaining that even 10% was probably more pain than the father had ever experienced before.
But as the labour progressed, the husband felt fine and asked the doctor to go ahead and bump it up a notch.
The doctor then adjusted the machine to 20% pain transfer. The husband was still feeling fine.
The doctor checked the husband's blood pressure and was amazed at how well he was doing. At this point they decided to try for 50%.
The husband continued to feel quite well. Since the pain transfer was obviously helping out the wife considerably,the husband encouraged the doctor to transfer ALL the pain to him.
The wife delivered a healthy baby with virtually no pain. The amazed doctor told the man that the pain he had endured would have killed any normal man.
She and her husband were ecstatic about their newborn and the pain-free way he was delivered.
Until they got home to find the milkman dead on the porch.