Shanghai First Maternity and Infant Hospital says it will cooperate with investigations into the possible switching of two babies 28 years ago after a 1.3 million yuan (3,000) suit was filed against it.
"In a statement on Saturday, the hospital said it was "deeply shocked and felt much sympathy for the family" filing the action.
"It's hard to find out the truth as it has been 28 years, but we will fully assist in the investigation," the statement said.
"If any blunder is found, we will be sure to take the due responsibility."
The Jing'an District People's Court confirmed to Shanghai Daily the suit had been filed, but did not say when the case would come to court.
The incident became public last Thursday when it was aired on Shanghai TV station.
The woman who filed the suit, surnamed Zhang, underwent a caesarean section and delivered a boy, called Wang Ye, on February 27, 1989.
Three days later, nurse brought the baby to her.
"It was our first meeting, as mothers and babies were accommodated on two different floors," Zhang told the TV station.
"It's strange that he kept crying and refused my breast milk, but he became silent when he was breast fed by a woman beside my bed."
Zhang and the baby returned home. But the father began to have doubts as Wang did not look like him. Rumors began that Zhang had had an affair, the program reported.
"He believed that I was errant. We broke up in 2003 and divorced the next year," Zhang told the program.
Her husband kept pursuing the issue and requested a DNA test in 2011, which showed that Wang wasn't related to either of them.
"I couldn't accept that I'm not their biological son." Wang told the reporter.
"I had thought that there must be something wrong, maybe technical problems."
Zhang thought of another possibility — that two boys were mistakenly swapped at birth.
So, she visited the hospital, hoping to read hospital records and find her true son. But she was only told that "records were too old to be found."
"I didn't give up and paid visits again and again, but later they just shut me out," Zhang said, adding that she had no choice but to file a lawsuit in 2016. And a second DNA confirmed the earlier result.
"I remembered that when nurse gave the boy to me, he didn't wear a bracelet or name card to show his identity," Zhang said. "Also, he was never away from home for long time."
Zhang and Wang say they now want to reunite with their "real" families.