Melinda Gates on contraception funding
11 July 2012 Last updated at 14:55 BST
The government says it will provide around £1.3bn over eight years to pay for family planning services in the world's poorest countries.
Ministers say the increase in aid will save a woman's life every two hours.
The pledge is being announced at a conference in London organised by Bill Gates's charity foundation and the Department for International Development, his wife Melinda said the money was vital.