Back in the 60s I was asked by a young Norwegian lady of my aquaintance if there was a birth control pill for men, when I told her that as far as I knew not yet, her response was "Oh shit" It appears that this guy had told her that he was on the pill and all was safe, so she gave in. She did admit eventually that she would probably have slept with him anyway so what the heck. So the 'I've had a vasectomy' ploy will work, but only if the girl wants to believe it; she could always check for a scar!
Giok

Snip snip; it will make a vas deferens to your life!