London - Governments and donor groups have pledged to provide access to family planning services to an additional 120 million women in many of the poorest countries by 2020.
The promise was made at the London Family Planning Summit, which was co-hosted by the British government and the Bill and Melinda Gates Foundation, set up by the Microsoft boss and his wife to improve global healthcare and tackle extreme poverty.
The Prime Minister, David Cameron, said giving women the freedom to choose when and how many children they had was "fundamental" to tackling global poverty.
Speaking to health leaders, Mr Cameron said: "A country cannot develop properly when its young women are dying from unintended pregnancy and when its children are dying in infancy."
Both the British government and the Gates Foundation have pledged to double their aid to family planning over the next eight years.
The British commitment will rise from £90 million ($150 million) to £180 million ($300m). In total, governments and charitable organisations promised nearly £3 billion ($4.8 billion) by 2020.
At present 220 million women do not have access to contraception or family planning services. It is estimated that a woman dies from pregnancy-related complications every two minutes.
The summit's organisers say the cumulative impact of the pledges by 2020 could be 200,000 fewer maternal deaths, 110 million fewer unintended pregnancies, 50 million fewer abortions, and nearly three million fewer babies dying in the first year of life.
Melinda Gates said: "When I travel and talk to women around the world they tell me that access to contraceptives can often be the difference between life and death.
Save the Children said child marriage was a key issue that needed to be addressed. It estimates that more than one in 10 girls is married before the age of 15.
Research has shown that the longer girls spend in education, the later they are likely to start a family and the more likely they are to be lifted out of poverty.
Last year the global population total reached 7 billion and it is estimated to reach 8 billion by 2025.