At least one woman dies during childbirth every minute in the developing world, health experts warn.
Pregnant women should have access to birth attendants, says the WHO
The World Health Organization is spearheading a campaign to reduce the numbers of women who die in this way.
It is calling for action to be taken to reduce the death toll of half a million women a year.
The WHO says women should have skilled birth attendants. It also wants better mortality data to improve knowledge of how many women die this way.
The WHO estimates that maternal deaths are under-reported by as much as 50% . In 62 countries, there is no data on maternal mortality.
The causes of death include haemorrhage, infection, obstructed labour and unsafe abortion.
But it says the underlying reason for women dying in childbirth is unavailable, inaccessible, or poor quality healthcare.
The WHO says around a million children are left motherless each year. These children are 10 times more likely to die in childhood than children whose mothers have not died.
It estimates the risk of dying in pregnancy in the world's poorest countries is over a hundred times higher than in the richest ones.
'Deaths are preventable'
The Millennium Development Goals which include a target to reduce maternal mortality by three quarters by 2015.
The WHO is launching a campaign to train health workers in high-risk countries.
It has produced a manual explaining why women die from complications related to childbirth, and sets out how this can be avoided by using effective and affordable.
The WHO says an extra US$10m is needed to train decision-makers, national health planners and medical service providers in these countries.
Joy Phumaphi, WHO Assistant Director-General on Family and Community Health told a meeting of health experts in Nairobi: "Pregnancy is a normal, life-affirming state. Women should not die giving birth.
"Their deaths are preventable, even in the poorest countries. But it takes local knowledge, strength and partnership to ensure women's lives are saved."
She added: "One key task of the global health community is to close the gap in services for women in rich areas, and those in poor ones.
"If dead women are not even counted, then it seems they do not count. We have an invisible epidemic."