Immigration officials will abandon efforts to spare most pregnant women from detention, according to new guidance issued by Immigration and Customs Enforcement (ICE) Acting Director Thomas Homan.

The announcement, made in a memo written by Homan last December but not revealed until Thursday, was condemned by immigrant rights advocates.

Homan’s memo, entitled “Identification and Monitoring of Pregnant Detainees,” reverses guidance put forth by former Homeland Security Secretary Jeh Johnson during the Obama administration, which stated, “Absent extraordinary circumstances or the requirement of mandatory detention, pregnant women will generally not be detained by ICE.”

Some pregnant women were detained under the earlier guidance—about 500 in 2016—but ICE will now err on the side of holding them in detention facilities rather than releasing them, as President Donald Trump continues his efforts to detain more immigrants than previous administrations.

Only women in their third trimester of pregnancy will still generally be released. Since the new policy went into effect, ICE has detained more than 500 pregnant women, according to the Huffington Post. As of March 20, 35 pregnant women were in immigration detention.

Christina Costantini, a journalist who has reported on immigration detention facilities, posted on social media about ICE’s extreme lack of preparation for—and interest in—providing proper care for pregnant women.

Two women told the Huffington Post last year that they had suffered miscarriages while in detention in immigration jails, and said that ICE employees had neglected to give them proper medical care.

“This new policy further exposes the cruelty of Trump’s detention and deportation force by endangering the lives of pregnant immigrant women,” said Victoria Lopez, senior staff counsel for the American Civil Liberties Union (ACLU), in a statement. “It removes critical protections for this vulnerable population and eliminates key reporting requirements for oversight of a detention system that needs more, not less, transparency and accountability.”