The United Nations estimate that this week, the world's population will reach seven billion. Most of the current population growth is taking place in the world's poorest countries.
This will add to the pressures that governments in these countries face to provide basic services like health and education for their people.
Combined with other pressures like climate change and water scarcity, this could mean even greater poverty for people already struggling. The lack of choice women and girls have over their own lives and bodies is a major cause of poverty and contributes to rapid population growth. For the millions of girls who are still children themselves, pregnancy means giving up school and the chance of an education that would allow them to support themselves and their families.
Today, 215 million women who would like to delay or avoid having children are unable to do so because they don't have access to modern contraception. Globally meeting this need for family planning could avoid around a third of maternal deaths and a fifth of newborn deaths, and save an estimated $5.1 billion dollars.
International Development Secretary Andrew Mitchell said:
"Some people think we're heading for a vast human tragedy if growth continues at the current rate - others think we'll cope and that the rising population is simply proof of increasingly sophisticated developments in medicine, agriculture and technology.
"It is not for DFID - or anyone - to say how many children people should have - that has to be a free choice. And providing choice for women has been my priority since starting this job.
"Giving girls and women in developing countries the choice to decide whether, when and how many children they have is saving lives.
"It means fewer women die in childbirth and the poorest families can make what little they have go further. Family planning is a smart and extremely cost effective investment of aid."
What is DFID doing?
We are committed to doing all we can to build sustainable growth and to tackle poverty.
We are putting girls and women at the very heart of all of our development efforts - this means we're supporting efforts to get more girls into and completing school.
We are determined to make progress in closing the family planning gap.
We are working closely with a number of other development partners to understand the role of population dynamics in helping to achieve increased economic productivity and rising per capita income in developing countries.