(CNN) A European doctor who provides abortion pills by mail to the United States is defying an order from the US Food and Drug Administration to stop.

"It is very important to continue ... because it is the only safe abortion alternative for some of the most vulnerable people," Dr. Rebecca Gomperts said in an emailed statement. "As a physician, I have the obligation to provide medical care to people in need."

A letter drawn up by Gomperts' attorney was sent to the FDA late last week, offering a formal response to the federal agency, which had asked the doctor in March to "immediately cease causing the introduction of these violative drugs into U.S. Commerce."

The FDA said in its warning letter , "the sale of misbranded and unapproved new drugs poses an inherent risk to consumers who purchase those products." But Gomperts called concerns about the medications she prescribes "totally unfounded" and said the FDA's restrictive handling of abortion medication is "based on politics, not science."

Dr. Richard Hearn, a longtime physician-turned-attorney in Pocatello, Idaho, is representing Gomperts. He argued in his letter to the FDA that the agency is overstepping its role in going after a doctor, targeting the distribution of this medication while ignoring other drugs purchased online, including Viagra, and disregarding the proven safety of this early-stage abortion method.

"The effect, if not the purpose," of the warning and restrictions is to "place a substantial burden in the path of U.S. women" who've "been forced to attempt to exercise their right to a medical abortion by way of the internet," he wrote.

Included with Hearn's letter was a 12-page list of 145 notes sent to Gomperts.

"It was assault, I'm homeless and trying to get off the street," one woman wrote. "I can't afford to get set back anymore. I can't do this and I don't want to. ... I want it to be over ASAP so please help me."

"The father had taken off the condom without informing me," wrote another woman, who said in her thank you note that she lives in the Bible Belt and worried that her family would shun her. "There's no way I could have gotten to the local clinic. Abortions are only available on a few days a week, and they're always at times I work. I also don't drive, so discreetly visiting the clinic wasn't an option."

"You all prepared me, answered my questions so quickly, I will always be grateful for you," a third woman said. "Between heart issues and the pregnancy hormones setting off my depression again to the point I wanted to die you guys saved my life."

How abortion pills by mail work

Gomperts' organization, Aid Access , uses telemedicine, including online consultations, to offer services to healthy women who are less than nine weeks pregnant. If a woman completes the consultation and is deemed eligible for an abortion by medication, Gomperts writes a prescription for the two pills used to terminate the pregnancy. Prescriptions are sent to a pharmacy in India, which fills and mails orders to the United States.

The first drug taken in the protocol is mifepristone, which blocks progesterone, a hormone that allows the pregnancy to continue. The second drug, misoprostol, stimulates the uterus, causing it to cramp, bleed and contract -- ending the pregnancy in what is "very similar to a spontaneous miscarriage," Gomperts explained.

Obtaining the drugs in the United States, however, can be challenging. Many states have laws that require patients to first be shown ultrasounds or sit down with doctors. For women who can't get to or afford a clinic visit, medication abortion might not be an option.

Plus, the FDA has imposed restrictions, such as requiring that providers have special certification to distribute the medication and that the medication be dispensed only in health-care settings.

Rules like these are celebrated by anti-abortion groups, which expressed outrage when they first learned of Aid Access.

"Handing out deadly drugs through the mail is a disaster waiting to happen," Kristan Hawkins, president of Students for Life of America, said in a statement last fall . "Risking women's lives to make a political point and a quick profit makes no sense, and we sadly anticipate horror stories when inevitably something goes wrong."

But clinicians and researchers often balk at these fears.

In the group's guidelines for managing first-trimester abortions , it says, "Medical abortion can be provided safely and effectively via telemedicine with a high level of patient satisfaction; moreover, the model appears to improve access to early abortion in areas that lack a physician health care provider."

Why Aid Access

Gomperts suggested in an email that the federal restrictions amount to hypocrisy.

"In direct opposition to its mission -- to protect the public health by ensuring the safety, efficacy, and security of drugs -- the FDA has so severely restricted access to these safe and effective pills that few doctors are willing or able to prescribe mifepristone and misoprostol," she wrote.

So through Aid Access, she began prescribing abortion medication to women in the United States last year. It was an outgrowth of her 13-year-old program Women on Web , which offers this kind of service to women in countries where abortion is illegal. The nearly 1,000 emails she'd received from people in the United States seeking help, some so desperate that they threatened to harm themselves, she said, prompted her to broaden her outreach.

"I realized it was time," she said last fall. "Something had to be done."

She has consulted "with women in all 50 states and the District of Columbia," attorney Hearn said in his letter to the FDA. "Of the 11,108 women who consulted with Dr. Gomberts in 2018, 2,581 were prescribed medicine approved by the FDA to induce a medical abortion during the early stages of their pregnancies."

Of those she's served, Hearn said, Gomperts is "not aware of a single death, hospitalization or serious complication attributed to the prescriptions she prescribed for her patients in the U.S."

There are other ways to get abortion pills by mail in the United States, for women who can't get to or afford clinic visits, but Aid Access is the most affordable option at $95, according to the grassroots group Plan C , which aims to educate women about self-managed abortion. Aid Access also offers the possibility of financial help, according to its website.

Plus, it's the single source to offer physician oversight, according to a Plan C report card

Aid Access is the only one of eight suppliers to receive a grade of A.

What happens next

A 2015 study showed abortions by medication to be about 97% effective. Interest in self-managing or self-inducing abortions is on the rise, according to reports.

In a one-month period in 2017, research published last year showed , there were nearly 210,000 US Google searches for information about self-abortion. This indicates a demand for alternatives, perhaps driven by barriers to clinic access due to financial hardship, geographic distance, fear of being publicly shamed or other reasons.

Hearn outlined further points of comparison to illustrate the safety of these abortions.

"Medical abortions have the same mortality rate as natural miscarriages, (approximately 1 death per 234,000 prescriptions)," he wrote. "That means that medical abortions are significantly safer than natural childbirth, (1 death per 3,788 births), penicillin (1 death per 100,000 prescriptions) and Viagra (1 death per 20,000 prescriptions)."

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US women "have a 60-fold higher risk of death from childbirth than from a medical abortion," he wrote.

The FDA, however, maintains its concern that drugs purchased online from foreign sources "are not the FDA-approved versions of the drugs" and, if unregulated, "may be contaminated, counterfeit, contain varying amounts of active ingredients, or contain different ingredients altogether," according to an email from the office of media affairs.

The federal agency would not comment on its next steps, in light of Hearn's insistence that his client would continue her work and not turn US women away. But its media relations department recounted its warning from the March letter, saying, "failure to correct the violations of the law may result in FDA regulatory action, including seizure or injunction, without further notice."

What that would look like in Gomperts' case is unclear, but Hearn is not concerned. He said that the FDA rarely enforces its warning letters, isn't in the business of regulating doctors and that it would be up to the Department of Justice to try to prosecute Gomperts.

Because Gomperts lives in Europe, he suspects that the Department of Justice wouldn't bother. But if it ever comes to that, he insists, he's prepared to stand and fight for her and her patients.