Correction, Section A (10/19/88): Regina Twigg, who filed a $100-million lawsuit saying a hospital swapped her baby for another one, knew three years ago that her legal daughter had a different blood type than she and her husband. But Mrs. Twigg said she did not know then that the girl wasn't her biological child. A headline in Friday's Times misstated her position.

In 1978 Mrs. Twigg had a baby girl at Hardee Memorial Hospital in Wauchula. A doctor pronounced the child healthy at birth. But before leaving the hospital, Mrs. Twigg learned that her daughter had a bad heart.

In their lawsuit the Twiggs said they first discovered Arlena was not theirs this year, after learning the results of test that showed the child had a blood type of B-positive. Mrs. Twigg and her husband have O-type blood.