Deaths of women from pregnancy-related causes have fallen by almost half across the world in the past quarter century.
But only nine countries have achieved the targets set by the UN, a report by UN agencies and the World Bank said on Thursday (local time).
"This report will show that by the end of 2015 maternal mortality will have dropped by 44 percent from its levels from 1990," said Dr Lale Say, co-ordinator for reproductive health and research at the World Health Organisation.
"This is huge progress but the progress is uneven across countries, across different regions of the world," with 99 percent of the deaths in developing countries, she told a news conference in Geneva.
The report, published simultaneously in the British medical journal The Lancet, said that in 2015 some 303,000 women died as a result of complications during pregnancy or up to six weeks after giving birth, down from 532,000 in 1990.
"This equates to an estimated global ratio of 216 maternal deaths per 100,000 live births, down from 385 in 1990," it said.
As part of the Millennium Development Goals adopted in 2000, UN member states pledged to reduce maternal mortality by 75 percent by 2015 from 1990 levels.
But only nine countries have achieved this target, although 39 others have registered "significant progress" in reducing maternal deaths, said Say.
The greatest improvement was in eastern Asia, where the maternal mortality ratio fell from approximately 95 to 27 per 100,000 live births.
Sub-Saharan Africa accounted for two out of every three deaths in the world.
"But that represents a major improvement: Sub-Saharan Africa saw nearly 45 percent fewer maternal deaths" over the period, the report said.
"Ensuring access to high-quality health services during pregnancy and child birth is helping to save lives," it said.
It said essential health interventions required include practising good hygiene to reduce infection, injecting oxytocin hormone immediately after childbirth to reduce risk of severe bleeding, and identifying potentially fatal conditions like pregnancy-induced hypertension.
The UN has now set a goal of reducing the global maternal mortality ratio to less than 70 per 100,000 live births by 2030.