A blonde calls a pharmacy and asks if she can get an infant scale to weigh a baby.
The clerk explains that many women figure out an infant's weight by weighing themselves while holding the baby on an adult scale, then the mother weighs herself alone and subtracts the second amount from the first.
"Oh, that won't work," replies the blonde. "I'm not the mother -- I'm the aunt."
Cheers,
Paul (A.)