The GOP's proposed Medicaid cuts could leave millions of women uninsured 17 million women in the U.S. ages 18-64 have health insurance through Medicaid.

 -- The Republican health care bill currently making its way through Congress could have a major impact on how many people have access to health services through Medicaid --changes that would fall disproportionately on women.

Today, more than 17 million women in the U.S. aged 18 to 64 have health insurance because of Medicaid, according to data from the National Women’s Law Center. Nearly a fourth of these women gained access to health insurance for the first time as a result of Medicaid expansion under the Affordable Care Act (ACA) that passed in 2010.

Just within the first two years of expansion, nearly four million women were newly insured through Medicaid between 2013 and 2015 -- women who are now at risk of losing health care coverage.

The Republican plan, known as the American Health Care Act (AHCA), could reverse these gains since the bill proposes drastic cuts to Medicaid. The safety-net program is projected to lose over $800 billion over 10 years, according to a newly released report from Congressional Budget Office (CBO).

Women, who are the primary beneficiaries of Medicaid, could be the hardest hit by these changes. In 2015 alone, nearly four million more women were using Medicaid than men according to the U.S. Census Bureau.

“Medicaid is a critical lifeline to health care services,” said Alina Salganicoff, vice president and director of women's health policy at the Kaiser Family Foundation. “Now, nearly one in five women have Medicaid coverage and anything you do to change Medicaid will impact women in this country, especially the women who have the fewest resources to get care.”

Medicaid expansion under the ACA discarded "categorical" eligibility -- where low-income individuals only qualified if they were pregnant, a parent of a dependent child, over age 65, or had a disability—in favor of criteria solely based on income. For the first time, it allowed low income women without children to gain access to health insurance.

Expansion was adopted by 31 states and the District of Columbia, and according to the National Women’s Law Center, these states saw the biggest leaps in Medicaid enrollment for women aged 18–64.

The CBO estimates that under the AHCA, Medicaid expansion would no longer be sustainable, with states curtailing their programs or choosing not to expand eligibility due to the lack of funds. By 2018 the CBO estimates that 4 million people will lose coverage with that number steadily increasing to 14 million by 2026.

The dramatic losses in insurance coverage are primarily driven by changes to Medicaid enrollment and funding under the legislation, according to the CBO. The AHCA would cut federal funds to match state budgets and place caps on the amount that can be spent for each Medicaid user.

Instead, the new bill proposes a system of block grants in which fixed amounts of money are doled out to states, allowing them to tailor health care services offered to their local populations.

“We believe that it's important to allow states to have that flexibility to fashion the program for their vulnerable population that actually responds to that population in a way that gives them the authority, them the choices, them the opportunity to gain coverage and the care that they believe most appropriate,” said Secretary of Health and Human Services Tom Price during a White House press briefing in March.

But Dr. Diane Cosper Horvath, a reproductive health advocacy fellow at Physicians for Reproductive Health disagrees, saying that the cuts to Medicaid would be “catastrophic to health care in our country.”

“When Medicaid gets cut, the people that are hurt the most are women,” she said. “Women who are heads of households, single mothers. People who are struggling to make ends meet, they lose insurance coverage and risk not being healthy enough to work and not being able to maintain their health well enough to care for their families.”

Since its inception in 1965, Medicaid has become a linchpin in America’s health safety net, especially for low-income women. The program is an important protection for vulnerable populations, providing coverage for nearly half of reproductive aged women living below the federal poverty line according to the Guttmacher Institute. Women of color are also more likely to rely on Medicaid -- the Kaiser Family Foundation found that one in four African American and Latina women using the program.

Medicaid provides access to a broad range of services integral to a women's health across her lifespan, including reproductive health care, maternity care, family planning, mental health, preventive cancer screenings, and treatment services.

Horvath, a practicing physician, has personally witnessed how health insurance can be the difference between life or death for many women. She recalls a patient from her early days of training: a young woman in her early forties who came to the hospital with advanced cervical cancer— a cancer that had progressed so far that not even a year later, she died, leaving three children behind.

Years ago, this woman had an abnormal Pap smear, but “she was too poor to buy insurance through work, but made too much to qualify for Medicaid,” said Horvath. Her patient would likely have been eligible for Medicaid under the current law.

Without insurance, this woman never sought out more medical care and succumbed to an illness that is eminently preventable, Horvath said.

“I think about how life would’ve been different for her if she was able to come in and get routine health care, it would have saved her life," Horvath said.

With millions of women at risk of losing access to health care, Horvath views the cuts to Medicaid as a part of a larger trend to disadvantage women.

“It’s a clear pattern of de-prioritizing women's health, reproductive health, and health and well-being of families,” she said. “This is really an assault on families in this country, low-income individuals, people of color. It’s terrifying.”