What condoms are the best for preventing pregnancy?

Any condom: All condoms if used as directed should be efffective in preventing pregnancies.

Any 1 U will use: Condoms go through rigorous testing and quality control. Any condom will prevent pregnancy if used appropriately and if it maintains it's integrity. If you are concerned, use condoms that purport to be a thicker condom. "thin" condoms may break easier. Unlubricated condoms may break easier. Too tight condoms may break easier. Partner help with using foam, film, suppositiory and other may help.

Condoms: Not the "cheapest;" but good quality ones that are used appropriately/correctly!