At the same time, a child born in a developing country is almost 14 times more likely to die in the first month than a child born in a developed country, UNICEF's "State of the World's Children" report said.
"The younger a girl is when she becomes pregnant, the greater the health risks," said the report released in Johannesburg, South Africa.
Girls who give birth before the age of 15 are five times more likely to die in childbirth than women in their 20s, the report said.
The child of a mother under age 18 has a 60 percent greater risk of dying in its first year than an infant born to a mother older than 19, the report said.
Ninety-five percent of the world's maternal deaths are in Africa and Asia, with 50 percent of the global total in sub-Saharan Africa and 35 percent in South Asia.
Those regions areas are also where child marriage is most prevalent, the report said.
The number of maternal deaths worldwide exceeds 500,000, including about 70,000 girls and young women age 15 to 19, the report said.
At least 9.2 million children died in 2007 before reaching the age of 5, down from 9.7 million in 2006. source