If a woman performs fellatio, they kiss, and then he performs cunnilingus, is there a pregnancy risk? what timeframe/method may reduce pregnancy risk?

Condoms: Pregnancy requires sperm to be deposited in the vagina around the time of ovulation so that an egg can be fertilized. It would be very inefficient to pass sperm from your penis to her mouth then to your mouth to her vagina. I suppose it is theoretically possible but I doubt it has ever actually occurred. You could avoid this worry by using condoms and or using birth control.