a state or condition in which a woman is so rotund that it is highly unlikely that a member of the opposite sex will engage with her in a procreative or other sexual act
"Suzie's lucky she's never had to worry about going on the pill," Erin cattily remarked. "With a figure like hers, she can always rely for protection on girth control."
A woman's state of being so overweight that nobody would want to have sex with her, thus reducing her chances of becoming pregnant to zero.
It looks like Kirstie Alley has gained another 100 pounds from her latest diet of Ben & Jerry's Cherry Garcia; she must be on girth control.