A global food crisis is making matters worse by pushing more families in the developing world to send young daughters into marriage to deal with poverty, the survey from humanitarian group World Vision found.

Child brides suffer because they often end their education early and are more likely to be injured or to die during childbirth because their bodies are not fully developed.

"Complications during childbearing and delivery are most common in this age set, significantly raising the risk of death, premature delivery, infant mortality and low birthweight," the report said.

An estimated 3,500 girls marry each day before their 15th birthday and another 21,000 do so before they are 18 -- figures the humanitarian group said would balloon in coming years.

While the practice occurs worldwide and in wealthy nations too, it is most common in sub-Saharan Africa, South Asia and parts of Central America, the report said.

The highest child marriage rates were in Bangladesh where nearly 53 percent of girls married before the age of 15, followed by Niger at almost 38 percent, Chad at about 35 percent, and Ethiopia and India at about 31 percent.

"It is most prevalent in communities and households where the starkest poverty mixes with cultural traditions and lack of education to limit a girl's perceived value and potential," it said.

Another issue is that many young brides are forced to have sex before their bodies are ready, and few have access to reliable contraception and reproductive health advice.

"Forced sex causes skin and tissue damage that makes a female more susceptible to contracting sexually transmitted infections from her husband," the report reads.

Raising awareness is key to stopping child marriage and using school and community workshops can help at risk families.