Once swallowed, the pill remains in the stomach for weeks, slowly releasing hormones to prevent a pregnancy.
It is specially designed to resist immediate attack by stomach acid.
A US team, funded by The Bill and Melinda Gates Foundation, has tested it in pigs and hopes human trials can start within a few years.
The researchers say it would be a good option for women who want to take a tablet for birth control, but are worried about remembering to take a daily dose.
