You pull out

Your balls are churning and you know that the point of no return is only seconds away. The writhing, bucking red head atop you is lost in her own throes of orgasm, utterly insensate to reason as she gasps and moans and shudders. It would be so easy to let go and flood her fecund womb, and while you know that your vasectomy has erased the chance of pregnancy, it might still upset the girl.

With a growl you roll yourself and the plunging girl to the side, pulling your cock out of her tight young cunt. You grasp your throbbing shaft, pumping it once before you explode, groaning as you spurt a thick rope of cream across her trembling belly. You pump yourself dry, decorating the writhing teen's flesh as she looks up at you with delighted, excited eyes.