More than 1,500 doctors and hospital staff have signed a petition opposing the partnership between UCSF and Catholic Dignity Health, as San Francisco’s public medical center expects to expand its affiliation with the faith-based organization.

Some of the Catholic hospitals require UCSF doctors to sign a document that declares certain medical procedures, including sterilization, “intrinsically evil.” And critics say that by declining to provide care — from abortions to transgender surgery — the Dignity Health hospital system discriminates against women and LGBTQ people.

UCSF faculty, students and their supporters say they’ll rally Tuesday, when UCSF and Dignity Health representatives will discuss their partnership at a meeting of the UC regents health services committee on the UCLA campus.

“We are deeply concerned, because fundamentally, Dignity Health decisions are made based on religious beliefs, not on the most up-to-date evidence to provide the best care for patients,” said Dr. Eleanor Drey, who teaches obstetrics and gynecology at UCSF and signed the petition opposing the partnership. Organizers began collecting signatures three days ago.

UCSF doctors have had privileges at Catholic hospitals for decades. But the medical center has had a formal affiliation with Dignity Health only since 2017, when it partnered with three: St. Mary’s and St. Francis in San Francisco, and Sequoia in Redwood City. Now, UCSF wants to add a fourth: Dominican in Santa Cruz.

UCSF is severely overcrowded, and that is only going to get worse as the region’s population grows and ages, said Barbara French, a UCSF spokeswoman. Under the agreements, capacity is expanded because UCSF doctors go can see their patients at the partner hospitals.

“It’s our job to ensure we can continue to meet patient needs,” said French, adding that UCSF also partners with more than a dozen other area hospitals. “It’s not necessary for all patients to come to (UCSF’s) Parnassus site. ... If I’m a UCSF patient, I’m going to get the same quality of care.”

Including abortions? “No, no. We’re not providing abortions at St. Mary’s. But not all hospital facilities provide all care,” French said.

The health center has about 17,700 faculty and staff members.

Of particular concern to critics is that the UCSF doctors have to sign God-affirming statements when working at the Dignity Health hospitals. Some, like St. Francis, require signing the “Statement of Common Values,” agreeing not to perform abortions or procedures like in-vitro fertilization, where conception occurs outside a woman’s body. Others, including St. Mary’s, require the more restrictive “Ethical and Religious Directives for Catholic Health Care Services,” which describes certain procedures, including sterilization, as “intrinsically evil.”

“That flies in the face of everything the UC medical system says it stands for,” said Phyllida Burlingame, director of reproductive justice and gender equity at the ACLU of Northern California. “That’s like saying it is acceptable for a Dignity hospital to discriminate as long as it has a sign out front saying, ‘No transgender people allowed.’”

The ACLU is suing Dignity Health on behalf of Evan Minton, 37, a transgender man whose 2016 hysterectomy was canceled the day before, when medical staff at Mercy San Juan Medical Center near Sacramento learned its purpose.

When he got the call, Minton said, “I was just blinded by my tears.” The surgery had been years in planning and was timed to coincide with another surgery to complete his transition.

A court ruled in favor of Dignity Health, and the case is on appeal.

Meanwhile, Dignity Health says it has never lost a discrimination case.

“The services available at Dignity Health hospitals are provided to all members of the community without discrimination, including services for transgender patients and other members of the LGBTQ community,” Dr. Todd Strumwasser, Dignity’s senior vice president for Bay Area operations, said in a statement.

St. Francis Hospital in San Francisco, for example, provides transgender surgery. And Minton, ultimately, did get the surgery he needed, at a different Dignity hospital.

Even so, “it was the discrimination that left, and continues to leave, a mark on my soul,” he said. “No one should be turned away for care or have to fight so hard to be served.”

Nanette Asimov is a San Francisco Chronicle staff writer. Email: nasimov@sfchronicle.com Twitter: @NanetteAsimov