"Pregnant Problems" joke

In a second grade sex education class, a little girl asks,
" Teacher, can my momma get pregnant?"
The teacher asks,
"How old is your mother?"
The little girl says,
"Forty."
The teacher says,
"Yes, your mother could get pregnant."
The little girl asks,
"Can my big sister get pregnant?"
The teacher asks,
"How old is your sister?"
The little girl answers,
"Nineteen."
The teacher says,
"Oh my sweet, yes, your sister certainly could get pregnant."
The little girl asks,
"Can I get pregnant?"
The teacher asks,
"How old are you?"
The little girl says,
"I'm seven years! ! old."
The teacher says,
"No, you can't get pregnant."
The little boy behind the little girl gives her a poke and says,
"See, I told you we had nothing to worry about."