PHOENIX — As tales of wretchedness and overcrowding in government border detention facilities abound, one group of migrants is particularly vulnerable: teen moms and pregnant girls without parents of their own.

Immigrant advocates and lawyers say the young mothers don’t get special medical consideration while they’re being crammed into U.S. facilities so packed that migrants are forced to sleep on floors or stand for days on end. As a result, the girls say they’re underfed, have poor hygiene and their babies get sick.

Their hardships aren’t over once they’re released, which can’t happen until a vetted sponsor — usually a relative — takes them in as their immigration cases wind their way through the courts. Their lack of legal status and inability to afford child care makes it nearly impossible for them to find a job, and staying in the U.S. legally is an uphill battle even if their children are American citizens.

“The average unaccompanied minor who’s coming is facing so many challenges because of lack of access to legal representation, issues in education, lack of support, lack of mental health treatment,” said Priya Konings, the deputy director of legal services for Kids in Need of Defense, which helps unaccompanied minors. “When you compound that with anything else such as being a young parent or being pregnant, everything becomes twice as hard.”

An attorney’s shocking discovery last month of an ailing 17-year-old girl from Guatemala cradling a premature infant inside a U.S. detention center prompted a national outcry and highlighted the challenges facing the teens. The mother had had an emergency cesarean section in Mexico in early May and crossed the border with the baby June 4. She was in a wheelchair in extreme pain when legal advocates found her.

The girl and her baby are doing well after leaving the processing facility in McAllen, Texas, said her attorney, Hope Frye. “The place where they are, it’s safe and the baby is the belle of the ball,” Frye said.

The accounts from lawyers and advocates come as U.S. immigration agencies have been struggling to handle a growing influx of migrants who cross illegally from Mexico and end up in the facilities of the ill-prepared and increasingly overwhelmed Customs and Border Protection, the first agency in charge of their detention.

CBP is supposed to release the unaccompanied children to Health and Human Services — which contracts with shelter providers — within 72 hours, but the overcrowding has created a backlog that has resulted in children sometimes spending weeks in the custody of the CBP.

Customs and Border Protection has said repeatedly that it is not equipped to handle the large number of families and unaccompanied children coming to the border, and says its agents aren’t trained to be caregivers.

The conditions have prompted protests such as one Thursday in Philadelphia in which about 300 people demonstrated outside the building housing the Immigration and Customs Enforcement office. Police say some members briefly interrupted the Salute to America parade and 33 were detained and cited.

Customs and Border Protection apprehended over 56,200 unaccompanied youths in the Southwest border from October to the end of May, compared to 50,000 in the last fiscal year.

It’s not known how many were pregnant or had babies. But the HHS’s Office of Refugee Resettlement says the agency has had about 500 teens with babies in its custody since October.

The trip to the U.S. can be particularly dangerous for pregnant teens, said Nicole Ramos, refugee program director for Al Otro Lado, an organization that helps asylum-seekers.

“I feel young pregnant girls are vulnerable to human trafficking,” Ramos said. “They’re kids, so they’re not savvy in all the ways of the world.”