The Supreme Court of Florida yesterday overturned the conviction of Jennifer Clarice Johnson, the first woman in the nation convicted of delivering drugs to her newborn infants through the umbilical cord in the seconds after their births.

Ms. Johnson, 26 years old, of Altamonte Springs, was charged and found guilty under laws intended to apply to drug traffickers. About 160 such criminal cases have been brought nationwide.

"It's a great victory for public health, for women and newborns and common sense," said Lynn Paltrow, litigation director of the Center for Reproductive Law and Policy, which provided legal representation for Ms. Johnson. "It's the first Supreme Court in any state to address a conviction of a pregnant woman for giving birth to a substance-exposed newborn. It's significant both because it's a unanimous decision and because now all the courts that have ruled on these cases say they're illegal, unconstitutional or both."

Ms. Johnson was charged with drug delivery in 1989 on the basis of tests performed after the births of two of her children. Investigators said a son born in 1987 and a daughter born in 1989 had tested positive for cocaine. In both cases, Ms. Johnson told her doctors that she had used cocaine in the day before the deliveries. Both children were born healthy and at full term. 375,000 Babies a Year