Pregnancy is the biggest killer of teenage girls worldwide, a charity has said.
Every year one million teenage girls die or are injured because of pregnancy or childbirth, according to Save the Children.
In a new report, the children's charity warns that girls under 15 are five times more likely to die in pregnancy than women in their 20s.
More than 25,000 girls under 18 are married every day, according to the report. Many quickly fall pregnant before their bodies have sufficiently developed.
"The issue of children having children - and dying because their bodies are too immature to deliver the baby - is a global scandal," said Save the Children's chief executive Justin Forsyth.
"This is a tragedy not just for those girls but also for their children - babies are 60% more likely to die if their mother is under 18.
"In the developing world, family planning isn't just a lifestyle choice. Children's lives depend on it."
The report also found that around the world, one in five girls are teenage mothers - having given birth to a child by the time they are 18.
Next month a family planning summit is to be held in London to discuss increasing the global availability of contraceptives and to empower women so they have more choices about sex.