The world has made headway against the practice of child marriage, but progress has been frustratingly slow, according to a new report by UNICEF.

The percentage of women age 20-24 who were married in their childhood fell from 23% to 19% in the past decade. And yet, every year, 12 million girls across the world are married before the age of 18.

"The report confirms that we have made progress in eliminating child marriage," says Claudia Cappa, a senior adviser at UNICEF and an author of the new report. "But the report also indicates that the progress is not universal and is not fast enough."

At the current pace, the report says, it will take 300 years to completely eliminate the practice – long after the original target of 2030 set by the United Nations' Sustainable Development Goals.

"The number of 300 years was striking," says Sarah Barnes, director of the Maternal Health Initiative at the Wilson Center in Washington, D.C. The fact "that we need to be moving at 20 times the rate that we're moving right now to meet our goals by 2030 was also quite telling that there is still so much to be done."

The report also notes that recent and ongoing crises, such as armed conflicts, climate-change-related disasters and the economic and social changes caused by the COVID-19 pandemic have further slowed progress. That turmoil increases economic insecurity, which pushes families into marrying their daughters off early.

"Child marriage is very much linked to poverty," says Cappa.

Why some countries are seeing a notable drop in child marriages

Most of the reduction in child marriages happened in South Asia, which is still home to about 45% of child brides worldwide.

Ethiopia, Rwanda and others have also made significant progress.

These countries have three things in common, says Cappa.

"They've all seen a reduction in poverty," she says. "They've also seen access to secondary education for girls, and employment opportunities for women."

These changes create more and better economic opportunities for girls, making child marriage a less attractive option for families.

"Child marriage is also in place because of social norms, because of the way in which societies see the role of girls in their families," she says. "So when their macroeconomic changes are in place, switching norms also becomes easier."

But many regions across the globe have yet to move the needle on child marriages, notably Latin America and Central and West Africa, including parts of sub-Saharan Africa known as the Sahel. The sub-Saharan region has 7 out of the 10 countries with the highest prevalence of child marriages today.

Cappa says in certain subregions of the Sahel, some 80% of women aged 20-24 had been married in childhood. "These are regions and parts of the world that have been characterized over decades by a high level of insecurity connected to climate, connected to conflict."

As a result, the region hasn't seen an improvement in economic conditions for girls, which usually leads to a decline in child marriages.

A family response to crisis: Marry their children

"When a family or a community experiences crises, there tends to be an increase in child marriages," says Barnes of the Wilson Center. "Research has shown that families view marrying their child as a protection for that child, whether that be financially or physical security or better social welfare for their family and that child."

And many countries are seeing a rise in child marriages as a result of multiple ongoing crises, including conflicts, climate change and COVID-19.

The report estimates that an additional 10 million girls will become brides by 2030 as a result of long term impacts of pandemic-related social, health and economic changes.

"COVID-19 has increased poverty and therefore has triggered some of the key determinants of child marriage," explains Cappa.

When girls are home from school, and families are facing financial crises, parents are more likely to marry their girls off, she says.

"It's one less mouth to feed," she says, "but also, fear of sexual violence and threats to family honor" lead families to seek out the perceived safety of a marriage.

Armed conflicts and climate change have a similar impact – by increasing uncertainty and driving up the number of child marriages.

Robbing kids of their childhood — and their future

In the long run, child marriages keep families trapped in poverty, and the practice has grave health consequences for girls, women and their children.

"Child marriage robs children of their childhood," says Cappa. "Girls are expected to take on adult responsibilities when they are not ready. They have children themselves when they are still too young."

"Girls who marry as children are less likely to complete secondary education," says Barnes. "This makes them less likely to be financially secure, and gives them less years of formal education, which limits years of emotional and intellectual growth."

It also limits a girl's reproductive autonomy — "her ability to decide when, if and how many children to have and with whom," adds Barnes.

Being married in childhood decreases her access to health care and increases her risk of maternal death and other long-term physical and mental health issues.

"Girls married early are also more likely to experience intimate partner violence [or] contract sexually transmitted infections, including HIV and AIDS. And they're also at a heightened risk for cervical cancer," says Barnes.

Teenage girls are more likely to face complications during pregnancy and childbirth, which, in turn, puts their and their infants' lives at a greater risk, says Barnes.

"Adolescent pregnancy and complications during pregnancy and childbirth is the number one cause of death for girls 15 to 19," she says, "Their bodies have just not fully matured to be able to carry a pregnancy without complications."

On the other hand, women who marry in adulthood see better economic and health outcomes for themselves and their children, notes Cappa. For one, adult mothers are more likely to complete secondary education.

"We know that children of educated mothers are doing better," she says. "They have better nutritional outcomes. They are more likely to be in school themselves. Women who are educated are also less likely to be supportive of corporal punishment, for example, or to experience domestic violence."

Stopping child marriages, therefore, is "not an individual issue," she says. It's an issue with broad implications on society. When such marriages are curtailed, she says, it's better for families, communities and humanity at large.