A urologist, Dr. Ajay Nangia of University Kansas Health System, explained to For the Win how this could happen even after the surgery was performed.
“Nangia explained that after the procedure, patients are told they have to use birth control afterwards for three months and then come back for a follow-up appointment to make sure they have what they call a ‘zero count’ of sperm.
‘We don’t know if he got any confirmation of his “zero”,’ Nangia said. ‘Surely by the fact that he had one kid after his vasectomy should have been a red flag.’
The other factor there is that even after a man is found to have a ‘zero count,’ there’s a 1 in 2,000 chance of pregnancy.
But there’s also the fact that the human body can do some extraordinary things. It’s also possible for something call “recanalization” to take place, in which the scar tissue in the blocked or tied-off end can form little holes in them and allow fluids — the ones used to procreate — to flow through.”