Singer and activist Annie Lennox is calling for governments to do more to tackle preventable deaths among pregnant women and new mothers.
A long-time campaigner on global issues, she's just been appointed a goodwill ambassador for UNAIDS.
The foundation set up by Bill and Melinda Gates will devote an extra £1bn to the issue over five years.
But the organisers of this meeting say a further £8bn is needed every year to achieve international targets.
Complications from pregnancy or childbirth kill 350,000 women around the world every year.
Often the deaths result from basic medical problems - such as haemorrhage or infections.
The theme underlying this conference is - we know what to do, so why isn't it getting done?
Governments are under pressure to increase their spending on maternal care, because an internationally agreed target to reduce the deaths is unlikely to be met.
Annie Lennox told BBC News: "From speaking to people who really know, the spend is actually peanuts. The amount of money that would need to be invested to save people's lives on a massive scale isn't that much.
"It's pretty obvious by now that this Millennium Development Goal won't be achieved. But if we walk away from it, nothing will happen. So that's why we're here.
"As a campaigner, you can feel frustrated. But ultimately it's a daily commitment.
"You want to get to the end result. Your actions speak louder than just the words you are using."
I asked Annie Lennox what drove her to pursue her campaigning.
She said: "I find it deeply fulfilling to be engaged with issues of human rights and injustice.
"I would be really bored with myself if all I did was shop and have my nails done.
"This is deeply emotionally, spiritually and intellectually rewarding. There's no money that can pay for that."
The head of UNAIDS, Michel Sidibé, praised the "passion, commitment and know-how" that Annie Lennox would bring to the ambassador's role.
In a separate development, abortion is proving a divisive issue here.
The Gates Foundation confirmed that its investment won't be used to fund terminations.
A pro-choice and sexual health organisation, IPAS, said this was "very regrettable", because it says backstreet abortions put millions of women at risk of losing their lives every year.
Melinda Gates also paid tribute to David Cameron for his stand on global health.
Last week, Mr Cameron announced a new £5m fund that will enable NHS staff to share their skills with health professionals from developing countries.
The Prime Minister said it was "shocking and shameful" that maternal mortality rates in some countries remained high.
Melinda Gates said: "The new UK government has stepped up with this announcement in the heat of a very tough budget discussion.
"It's strong leadership and exactly the kind of move we need."