United Medical Center in Southeast Washington. (Sarah L. Voisin/The Washington Post)

D.C. regulators ordered the only full-service hospital in Southeast Washington to stop delivering babies last week because of dangerous mistakes the hospital’s staff made with multiple pregnant women and newborns, a letter obtained by The Washington Post shows.

In one case, the hospital’s staff members did not take critical steps to prevent the transmission of HIV from an infected mother to her newborn, such as delivering by Caesarean section or treating the infant shortly after birth with antiretroviral medication, according to the letter, written by D.C. Health Department Director LaQuandra Nesbitt to the hospital’s chief executive.

In another, a morbidly obese woman who was about 35 weeks pregnant and had come to the hospital with trouble breathing was not properly monitored or treated, despite a history of potentially fatal blood-pressure problems.

The letter does not state what happened to either woman, or to the newborn or fetus, and does not identify them by name.

The Aug. 7 letter provides the first official explanation — albeit an incomplete one — of why the Health Department took the dramatic step that day of closing the obstetrics ward at United Medical Center, a public hospital that serves the poor and predominantly African American residents of the neighborhoods east of the Anacostia River.

Officials in Mayor Muriel E. Bowser’s administration and Nesbitt, an appointed member of her Cabinet, have refused repeated requests from journalists and D.C. Council members to disclose the medical lapses that caused the closing of the hospital’s delivery rooms and nursery. They have also declined to release the letter obtained by The Post.

In an interview Friday, Nesbitt repeatedly refused to say why her staff had shuttered the public hospital’s obstetrics ward, asserting that to do so would violate the confidentiality of patients.

“We found things that led us to decisions to restrict the hospital’s license to not provide scheduled deliveries and the subsequent newborn nursery services that would occur,” Nesbitt said, declining to specify what those issues were.

Pressed about public concern over medical lapses at the hospital, Nesbitt was firm.

“There’s a difference between using the word ‘conceal’ as a journalist and recognizing that a government has the legal right not to disclose certain information,” she said, when asked why health officials were concealing the medical mistakes they discovered.

Hospital managers have also not publicly disclosed details surrounding the closure, saying in a statement last week it had been caused by “three separate cases involving deficiencies in screening, clinical assessment and delivery protocols.”

The statement said federal privacy laws “preclude sharing specific details of these cases, however, UMC is taking immediate action to address these deficiencies.”

Health policy experts said it was not unusual for government officials to be tight-lipped about reasons for shuttering or restricting hospital services, although inspection records are generally public. The federal Center for Medicaid and Medicare Services, for example, posts inspection reports online for some hospitals.

Too often, however, patients’ privacy is used as a pretext for withholding information the public deserves to know, said Rosemary Gibson, a patient advocate and adviser at the Hastings Center research group.

“The entire system is based on trust. Without being completely open and honest with the public, how can the public know if a place can be trusted?” Gibson said. “If there was a single patient or very small number of patients, patient privacy might come in to play. But most often, patient privacy becomes a cloak of secrecy to prevent the public from knowing risks that were allowed to fester.”

D.C. Council member Vincent C. Gray (D-Ward 7), the council’s health committee chairman, said in a statement Monday that the Health Department’s refusal to disclose information to lawmakers or the public was “unacceptable.”

Nesbitt’s letter to hospital chief executive Luis A. Hernandez, written in highly technical medical language, does not answer key questions about lapses in the obstetrics ward — including what happened to the mothers and infants who were involved in those lapses.

The letter lays out two categories of violations: failure to comply with standards of good medical practice and failure to report a case of HIV infection.

In the case of a woman referred to only as “Patient A,” who was infected with HIV and had a high viral load at the time of delivery, the letter states that the hospital did not deliver her baby by Caesarean section, which reduces the likelihood the virus will be transmitted to the baby.

The hospital also did not conduct a common test for the presence of HIV in newborn or treat the infant with the antiretroviral drug Nevirapine between 48 and 72 hours after birth, as recommended. Nor did it report the mother’s HIV infection to the Health Department, as required by law.

Hospital staff members did not properly monitor a second woman, “Patient B,” who was about 35 weeks pregnant and was in “acute respiratory distress” when she came for treatment. The woman had a history of pre-eclampsia, a blood-pressure condition that can be fatal for both mother and baby. In a third case, a newborn referred to as “Infant A” was not physically screened at the right time after birth.

Emma Brown contributed to this report.