Can air bubbles trapped in the vagina prevent conception? i lay on my back for hours after intercourse only to "fart" it all out when i get up.

Physiology: I have never once heard this before from any patient. No. The simple answer is that air in the vagina from intercourse in no way changes the anatomy or the action of semen and sperm. There is no reason to hold on to air. There is no reason to lay for hours in an attempt to increase your chances of pregnancy. I cannot imagine why you have gotten into this practice.

Unlikely: The sperm will move into cervix and uterine cavity.