BALTIMORE (AP) _ A couple who filed a $100 million lawsuit claiming that a hospital switched their healthy baby for one with a fatal heart defect nine years ago say they hope medical records will uncover their real daughter.

Ernest and Regina I. Twigg allege that Florida hospital workers changed identifying bracelets and altered records to give the Twiggs' healthy baby to an adoptive family, then gave the Twiggs an infant born the same day with a congenital heart defect.

''We're totally devastated,'' Mrs. Twigg told The (Baltimore) Sun. ''Our lives have turned into a nightmare. We've not only lost our Arlena ... but also where is our own daughter?''

The couple raised Arlena Twigg as their own until she died in August following surgery to correct the heart defect. Shortly before her death, the lawsuit said, a blood test performed at Johns Hopkins University here revealed that the child was not related to either parent.

The test showed Arlena had a blood type of B-positive. The Twiggs said their baby had been born with a blood type of O-positive, and they also both have type O blood.

Additional tests on Arlena's tissues also concluded it would be all but impossible for Arlena to be their child, said the couple's attorney, Marvin Ellin of Baltimore.

Mrs. Twigg later recalled that on the day her baby was born, a nurse told her another woman on the maternity ward had also delivered a daughter, which she intended to give up for adoption, the suit said. Those were the only two girl babies in the ward at the time, Ellin said.

Mrs. Twigg said she told a nurse shortly before leaving the hospital that the child she was nursing did not look like the same baby she had nursed earlier in her stay, but the nurse dismissed the notion.

The lawsuit, filed Wednesday in U.S. District Court in Tampa, Fla., asks for hospital records that Ellin said could help the Twiggs find out who adopted the girl. The attorney said he has also contacted the FBI.

The suit names Hardee Memorial Hospital in Wauchula, Fla., three physicians and a nurse, charging them with fraud or negligence, or both.

A woman who answered the telephone Thursday at the Twiggs' home in Langhorne, Pa., referred calls to Ellin.

The suit said that after the baby was born, the Twiggs were originally told that she was healthy but three days later were told she had congenital heart disease that could eventually prove fatal.

One of the defendants, Ernest Palmer, a family doctor, told The Sun, ''I certainly wouldn't switch babies on anyone, but I guess you can be sued by anyone.'' Harold Connelly, hospital administrator, said he had no knowledge of the suit and was surprised by the allegations.

Attempts by telephone to reach the other defendants - Dr. William D. Black, an obstetrician; Dr. Adley Z. Sedaros, a pediatrician; and Dena E. Spieth, a nurse - were unsuccessful.

The suit said the unknown adoptive parents wanted a healthy baby but it gave no reason why the medical personnel might have gotten involved in switching two babies. Ellin said some defendants may have been only negligent, but that at least one of them must have deliberately switched the two babies' bracelets.

The suit seeks records of payments to the defendants that might give insight into motives as well as indicate where the other child is living, Ellin said.