Gaining a little weight are we sister Susan?

A nun was walking in the convent when one of the Fathers noticed she was gaining a little weight. 

"Gaining a little weight are we sister Susan?", he asked.

"Oh no, Father. Just a little gas." Sister Susan explained, matter-of-factly.

A month or so later the Father noticed that she had gained even more weight. 

"Gaining some weight are we Sister Susan?", he asked again.

"Oh no, Father. Just a little gas." She replied again.

A few months later the Father noticed Sister Susan pushing a baby carriage in the convent.

He leaned over and looked in the carraige and said - "What a cute little fart!"