Washington (CNN) Over a dozen Democratic senators, including numerous presidential hopefuls, are demanding the reinstatement of an Obama-era policy against holding pregnant migrants in detention centers.

In a letter to Ronald Vitiello, the acting director of Immigration and Customs Enforcement, and Customs and Border Protection Commissioner Kevin McAleenan, lawmakers referenced reports of miscarriages and mistreatment of pregnant women following the Trump administration's repeal of a policy which required the immediate release of pregnant women last year.

"In addition to receiving inadequate medical care, women report having been shackled around the stomach while being transported and mistreated physically and psychologically by ICE and CBP agents," the letter says. "Women have shared stories of being ignored during their miscarriages by agents who refused to respond to the medical emergencies these women were facing."

The request comes in the middle o f major personnel changes in the Department of Homeland Security , seemingly driven by the administration's desire to get tougher at the border. The changes include the departure of Homeland Security Secretary Kirstjen Nielsen, the withdrawal of the nomination for Vitiello to be made permanent the director of ICE and pending appointment of McAleenan as acting secretary.

As the administration denies reports that President Donald Trump is looking to reinstate a zero-tolerance policy of family separation at the border, the senators argued that ICE is incapable of caring for pregnant women in their custody. Therefore, they said the agency should release the women upon detainment.

According to the ICE website and spokesperson Danielle Bennett the agency currently addresses pregnant migrants on a "case-by-case" basis. The agency provides a variety of prenatal and postpartum care and education as well as abortion services in some cases, Bennett said. ICE declined to comment on the letter.

"Such disturbing incidents underscore the need to return to ICE's previous policy of presumptive release for all pregnant women," the letter says. "ICE does not and cannot meet the medical, mental health, and nutritional needs of pregnant women in immigration detention."

According to the letter, 28 women have had miscarriages in ICE custody the last two fiscal years, citing figures officials gave to the Arizona Republic newspaper in February.

The senators called for the agency to ensure appropriate treatment of pregnant women in custody. They also requested documents and information regarding the number of pregnant women in detention since 2017, their condition and protocol for their care.

The letter was signed by 2020 presidential hopefuls such as Sens. Kamala Harris, Bernie Sanders, Kirsten Gillibrand, Amy Klobuchar, Elizabeth Warren, Michael Bennet and Cory Booker as well as other Democratic Sens. Catherine Cortez Masto, Ed Markey, Patty Murray, Ron Wyden, Jacky Rosen, Mazie Hirono, Bob Menendez and Tina Smith.