Hi!
All of the barrier methods prevent conception: condoms, diaphragm, female condom, etc.
Oral contraceptives prevent ovulation and therefore prevent conception.
Other hormonal methods such as depo provera and implants also work the same way.
Two methods which PROBABLY DO NOT work by preventing implantation of an embryo, but ARE controversial, and if you were my patient, I would advise you to avoid would be the intrauterine contraception device and the morning after pill. Both of the methods probably work by a different mechanism in the majority of cases, but theoretically could prevent implantation of an embryo which some consider to be an abortion.
The IRREVERSIBLE methods ( tubal/vasectomy/Essure) work the same way that the barrier methods work, but should not be considered until the family is complete.
I hope this is helpful information!
Dr B