When I first met Genet, it was hard to believe she was actually 13. She was incredibly small physically – no taller than my 7-year-old son — and intensely shy. She was so obviously a child that it was equally as difficult to wrap my head around the fact that she was married and on her way to having children of her own.

Genet had come to participate in a program called TESFA that is run by CARE and evaluated by my organization, the International Center for Research on Women (ICRW). It teaches married girls in the remote Amhara region of Ethiopia the important life skills they missed out on in part because of their marriage. On the day my colleagues and I met Genet, we learned that she had been married for two years. She had dropped out of school shortly before she wed her now-husband, whom she met on the day of her marriage ceremony. And like many child brides, Genet wasn’t able to articulate any dreams or hopes she had for her future aside from her role as a wife and, eventually, a mother.

While most child brides are wed when they are older than 11 — Genet’s age when she married — one in nine child brides today are married before they reach the age of 15. And over the next decade, an estimated 142 million girls will join Genet as child brides worldwide, or roughly 38,000 per day. This is why it is imperative that global policy makers determining the next generation of Millennium Development Goals (MDGs) keep young married girls — and those at risk of becoming child brides — at the forefront of their agenda. Eradicating and addressing the effects of child marriage has the potential to influence the success of every single goal identified in a UN Secretary-General’s high-level panel report as being crucial to success of the post-2015 development agenda. Not only are these girls too often forgotten; we also cannot afford to ignore their plight any longer.

Moving forward, ending child marriage — and, importantly, supporting married girls like Genet – deserves renewed attention and investment as a core target under the goal of empowering women and gender equality. It is time for policy makers to make this a significant priority that cuts across all other MDGs for 2015 and beyond.

After all, this is a practice that has tremendous ripple effects for not only millions of individual girls, but also their families, communities and countries: It perpetuates poverty. It hinders economic growth in emerging nations. It contributes to maternal and child mortality and illness. It guarantees that fewer girls are educated and that fewer women participate in the labor force. It ensures a less inclusive and less sustainable development process.

And at its core, child marriage reflects the scant value societies place on women and girls; universally, where child marriage is common, women’s basic rights are denied. Little girls like Genet are robbed of their childhoods when they are forced to wed. Child marriage strips them of the opportunity to go to school, to get a job, to live a healthy life, and to decide when and how to form their families.

These losses ultimately prevent girls like Genet from contributing to society as fully as they would otherwise: Child brides are less likely to be able to work outside the home, particularly in better paying jobs that require higher levels of education. This in turn makes them ill-equipped to earn additional income for their families. At the community level, married girls’ low social status means that they are less involved in political and social processes, further increasing their isolation. Meanwhile, children of child brides are more likely to have a limited education and to be poor and unhealthy, thereby further contributing to the intergenerational continuation of poverty.

If the global community fails to comprehensively address child marriage in the coming years, child brides, shamefully, will continue to represent a population of youth that has been largely left behind – even as the past decade has seen dramatic declines in poverty and poor health.

Traditionally, many child brides remain mostly invisible in government statistics. They are not in school, they’re not officially registered as being married, they use very few government services and they have not accessed health services. Most child brides fall through the cracks, practically disappearing in terms of official statistics. Tragically, married girls are also often invisible in terms of development policy, with governments and development program professionals focusing primarily on preventing early marriage, often at the expense of those who have already married. A dual approach is sorely needed.

In the coming decades, let’s not forget these children who have, against their choice, become wives and mothers all too soon. In setting the global development agenda, the goal should not be just to influence policy change — after all, virtually all countries are in agreement that child marriage is a violation of human rights — but rather one that is a firm call to action. It is time for the platitudes to end and actual change to begin for millions of girls like Genet around the world.

This post is part of a series produced by The Huffington Post and the NGO alliance InterAction around the United Nations General Assembly’s 68th session and its general debate on the Millennium Development Goals (MDGs), “Post-2015 Development Agenda: Setting the Stage” (September 24-October 2, 2013). The session will feature world leaders discussing progress made on the MDGs and what should replace them when they expire in 2015. To read all the posts in the series, click here; to follow the conversation on Twitter, find the hashtag #No1Behind. For more information about InterAction, click here.