Masaka: Would a 15-year-old girl be married off by her parents in violation of the law? Would another girl, who looks even younger, get justice after an alleged statutory rape at the hands of an older man?

In their impoverished communities in Uganda, the answers hinged on the fact that one girl had a birth certificate and the other didn't. Police foiled the planned marriage after locating paperwork that proved the first girl was not 18 as her parents claimed. The other girl could not prove she was under the age of consent; her aunt, who's also her guardian, has struggled to press charges against the builder who seduced and impregnated her, reports AP.

"The police were asking me many questions about proof of the girl's birth date," said the aunt, Percy Namirembe, sitting in her tin-roofed shantytown home in Masaka near the shores of Lake Victoria in south-central Uganda. "I don't have evidence showing the victim is not yet 18."

As Namirembe spoke, her niece sat beside her, her belly swollen and a vacant stare on her face. In the developed world, birth certificates are often a bureaucratic certainty. However, across vast swaths of Africa and South Asia, tens of millions of children never get them, with potentially dire consequences in regard to education, health care, job prospects and legal rights. Young people without IDs are vulnerable to being coerced into early marriage, military service or the labor market before the legal age. As adults they may struggle to assert their right to vote or inherit property.

"They could end up invisible," said Joanne Dunn, a child protection specialist with UNICEF. With support from UNICEF and various non-governmental organizations, many of the worst-affected countries have worked to improve their birth registration rates. In Uganda, volunteers go house to house in targeted villages, looking for unregistered children. Many babies are born at home, missing out on registration procedures that are being modernized at hospitals and health centers. By UNICEF's latest count, in 2013, the births of about 230 million children under age 5 - 35 percent of the world's total - had never been recorded. Later this year, UNICEF plans to release a new report showing that the figure has dropped to below 30 percent.

India is the biggest success story. It accounted for 71 million of the unregistered children in UNICEF's 2013 report - more than half of all the Indian children in that age range. Thanks to concerted nationwide efforts, UNICEF says the number of unregistered children has dropped to 23 million - about 20 percent of all children under age 5.

Uganda is a potential success story as well. UNICEF child protection officer Augustine Wassago estimates that Uganda's registration rate for children under 5 is now about 60 percent, up from 30 percent in 2011.

While obtaining a birth certificate is routine for most parents in the West, it may not be a priority for African parents who worry about keeping a newborn alive and fed.

Lack of registration hampers Uganda's efforts to enforce laws setting 18 as the minimum age for marriage. Child marriage remains widespread, due largely to parents hoping to get a dowry from their daughters' suitors. Even when the police are alerted, investigators face an uphill task pressing charges if they cannot prove, with a birth certificate or other official document, that the girl is a minor.

But in the recent case in the Rakai administrative district, police detective Deborah Atwebembeire was able to prevail in a surprise raid on a wedding party because the bride-to-be's birth certificate proved she was 15.