A newlywed couple goes to the hospital to give birth to their baby.

When they arrive, the doctor says that he invented a machine to transfer part of the labor pain of the mother to the father of the baby. He then asks if they agree.
The couple accepts gladly the procedure.
The doctor puts the machine at 10% for starting, explaining that even the 10% it's probably more pain that the father could ever bear.
But when the labor started, the husband was feeling okay and he asked the doctor to raise the level.
The doctor raised the transfer to 20%. The husband was still feeling good. The former checked the blood pressure of the latter and he was surprised by how good he was reacting.
At this point, both decided to raise the transfer up to 50%. The husband was STILL feeling good.
Since the transfer of pain was really helping the wife, the husband encouraged the doctor to transfer ALL the pain to him.
The woman gave birth to a healthy child and virtually with no pain. She and her husband were really happy.
When they got home, they found the mailman dead on the porch.