I just found out today that i am 2-3 weeks pregnant and i'm due to be sedated for a minor dental operation tomorrow, can this effect the pregnancy?

Don't: Most of the drugs used in dental sedation can have a negative effect on the baby. Get an ok from an OB doctor first.

Yes: Normally, you can use local anesthetic (lidocaine) for necessary dental procedures in the 1st trimester, but you should avoid general anesthesia and oral sedation drugs as they can also sedate the fetus. If the operation is "minor" as you say above, there should be no reason you would actually need sedation, from a pain perspective. The nervousness can be handled by a competent staff and dentist.

Yes, reschedule: There is risk (small) of problems during the first trimester of pregnancy with any dental work. If it is a minor procedure you are scheduled for, why take the risk to you and the baby, no matter how small?! rescedule for sometime during your second trimester--by then the risk is almost non-existent. If you wait til third tri, you might be too uncomfortable because of the baby's size.