This post originally appeared on MSNBC here. Reposted with permission.

In the U.S., the average girl can pour herself a glass of clean water when she’s thirsty. She can walk to school on paved streets without sewage getting in her way. And, when she matures, she can easily purchase feminine hygiene products and use a private restroom at her convenience. Her period is a nuisance, but it does not disrupt her day – or her life.

This is not the reality for the world’s poorest girls and women. Basic necessities — safe water, sanitation and hygiene supplies — are scarce and often unavailable to girls and women living in poverty. These stark conditions jeopardize the health, education and well-being of girls and women in ways the average American cannot, and does not have to, imagine.

For millions of girls living in poverty, starting their period could mean ending their education. When girls do not have access to cheap sanitary supplies, or a safe, private bathroom, they can miss up to 20% of the school year. That’s a week of school each month. Additionally, some cultural norms prohibit girls and women from being in contact with other people while menstruating. Both scenarios significantly set girls back in school, and many drop out entirely, ultimately enhancing the risk of continuing the cycle of poverty for herself and her family.

One solution to reduce unnecessary school absences and drop outs is to provide girls with low-cost, reusable sanitary napkins. AFRIpads, a Ugandan social enterprise that was named one of Women Deliver’s 50 inspiring innovations in 2012, provides menstrual kits that last for up to one year and are one-fifth the cost of other brands. Sustainable Health Enterprises (SHE) is another promising initiative that developed a new brand (go!™) of affordable, eco-friendly pads made from banana fibers. By 2017, SHE hopes to deliver these low-cost pads to more than 250,000 girls and create 1,200 jobs in the process. These are seemingly simple innovations, but their impact is life-changing.

Lack of clean water also has an enormous impact on girls’ opportunities to learn and grow. Girls and women are disproportionately tasked with finding water, and in many places, this can mean spending up to six hours trekking through unsafe terrain each day. Consequently, girls are late to class and already exhausted by the time they start the school day. In the worst cases, girls miss the whole school day and eventually drop out.

But when clean water is nearby, girls can spend less time gathering water and more time in school. In an effort to bring safe water closer to home, organizations like Water.org, partner with community members to build and finance water and sanitation improvement projects, such as local wells. Similarly, UNICEF’s Water, Sanitation and Hygiene (WASH) helps supply clean water and sanitation facilities in schools across more than 100 communities.

We know that investments in girls and women have enormous ripple effects on development, and solutions like these are helping them thrive. Educated girls and women are more likely to delay marriage, seek sexual and reproductive health services and have children later — all of which help them and their families lead productive lives.

The takeaway here is that when girls can overcome poverty’s obstacles, they stay in school, raise healthy families and grow economies. Everyone wins.

The unfortunate fact is that there are still more than a billion people living in extreme poverty — and the majority are girls and women. Nearly a billion people do not have access to safe water and twice as many are living without proper sanitation. Now is the time to change this reality.

Global leaders and advocates will arrive in New York at the United Nations General Assembly later this week to discuss some of the most important global issues of our time, including the next global development agenda. We must use this opportunity to remind our leaders that investing in girls and women — in their health, rights and well-being — is not only the right thing to do, it’s also the smart thing to do. Together, we must give today’s girls the opportunities and tools they need to become tomorrow’s leaders.