Women taken into custody by U.S. immigration agents while pregnant say they received inadequate care in a letter Wednesday that calls on the Trump administration to stop holding expectant mothers in federal detention facilities.

The letter to U.S. Immigration and Customs Enforcement is part of a broader campaign in recent months by Democrats and immigrant rights groups to draw attention to what they say is the mistreatment of pregnant detainees.

The Department of Homeland Security has defended its care, saying pregnant detainees get regular prenatal visits, mental health services, nutritional support and accommodations "aligned with community standards of care."

In addition, Homeland Security Department Assistant Secretary Tricia McLaughlin said in a written statement Wednesday that such detentions are "rare" and involve "elevated oversight and review." The agency didn`t provide figures on the number of pregnant women in detention, a number Democrats have sought for months.

The letter sent by the American Civil Liberties Union cites accounts from pregnant women who say they were shackled while being transported, placed in solitary confinement for multiple days and given insufficient food and water while detained in Louisiana and Georgia.

The ACLU said that over the past five months it has met with more than a dozen females who were pregnant while in ICE custody - including some who had a miscarriage while detained. The women reported "gravely troubling experiences," the letter states, including lack of translation during medical encounters and medical neglect. One suffered a "severe" infection after her miscarriage.

In an interview with The Associated Press, one of the women said she was kept in handcuffs while being transported to Louisiana - a journey that lasted five hours and spanned two plane rides. The woman, who has since been released from custody and given birth, spoke on the condition of anonymity out of fear of facing retaliation during her ongoing case.

An officer told her he considered taking off the handcuffs but worried she would escape. "How am I going to escape if I`m pregnant?" the woman said she responded.

She said she felt as if she`d been kidnapped and experienced dizziness, nausea and vaginal bleeding. During her time in detention, she said pregnant women were not offered special diets and described the food as horrible. She alleged that detainees had to "beg" for water and toilet paper.

The ACLU`s letter is the latest call for an investigation into the arrests and treatment of pregnant detainees.

Senate Democrats wrote Homeland Security Secretary Kristi Noem in September, expressing concerns about the "prevalence and treatment" of pregnant, postpartum and nursing women in ICE custody. They demanded that the agency stop detaining such people unless there are "exceptional circumstances."

"Proper care for pregnancy is a basic human right, regardless of whether you are incarcerated or not and regardless of your immigration status," said Rep. Sydney Kamlager-Dove, a California Democrat. She signed onto a Democratic Women`s Caucus letter to DHS officials in July sharing concerns about the "treatment of women" and demanding answers - including how many have given birth while detained.

Kamlager-Dove said she`s working on legislation that would "severely restrict the use of restraints on pregnant, laboring and postpartum women who are in federal custody."

ICE guidelines already say that agents "should not detain, arrest, or take into custody for an administrative violation of the immigration laws" people "known to be pregnant, postpartum or nursing," based on a policy sent to the AP by DHS. But the document does state that such people may be detained and held in custody under "exceptional circumstances" or if their release is prohibited by law.

The policy also prohibits using restraints on pregnant detainees, but here too there are exceptions - including if there is a serious threat that the detainee will hurt herself or others, or if "an immediate and credible risk" of escape cannot be "reasonably minimized" through other methods.