"Off To Rome" joke

Mrs. O'Donovan was walking down a street in Dublin and coming in the opposite direction was Father O'Reilly.
"Hello," the Father said, "and how is Mrs. O'Donovan? Did I not marry you a couple of years ago?"
"That you did, Father," she replied.
"And are there any little ones yet?" he asked. "No, Father, not as yet," she replied.
"Well, I'm off to Rome next week and I'll light a candle for you," said Father O'Reilly. "Thank you, Father," she replied and continued on her way.
A few years later they met again. "Well now, Mrs. O'Donovan," the Father said, "how are you?" And tell me, have you any little ones yet?"
"Oh yes, Father," she replied. I've had three sets of twins and four singles - ten in all."
"Now is't that wonderful," he replied. "And how is that lovely husband of yours?"
"He's well, Father. He's gone off to Rome for a wee spell," she said.
"And what would he be doing in Rome?" asked the Father.
"Blowing out that fucking candle!" she answered.