The Drexel University freshman who allegedly hid her dead baby in her car trunk last month had told the father that her pregnant belly was an "allergic reaction to a birth-control patch and that she planned to have the mass surgically removed," Upper Darby police said yesterday.

Police Superintendent Michael Chitwood said detectives found no evidence that the 18-year-old woman ever received such a medical diagnosis or treatment.

The father, an 18-year-old Haverford man who was the woman's high-school sweetheart, told police he had not known that his ex-girlfriend was pregnant, Chitwood said.

Investigators haven't filed any charges against the woman, because Delaware County Medical Examiner Dr. Fredric Hellman hasn't ruled yet whether the full-term newborn was born dead or alive.

Police found the lifeless boy on Jan. 22 naked, stuffed into a tote bag and buried under bloodied clothing and scattered mail in the trunk of a Volkswagen Beetle parked outside the Drexel Hill home of investment bigwig Albert E. Piscopo, the woman's grandfather.

Detectives suspect the baby had been dead at least a week, Chitwood said.

Police found "denial of pregnancy" information in the Drexel Hill home of the woman's parents. They also seized computers and carpet samples from outside a basement bathroom.

Detectives haven't questioned the woman yet, because they're awaiting the coroner's ruling before proceeding with a homicide or desecration-of-a-corpse case, Chitwood said.

Hellman said his ruling could take "at least a number of weeks but possibly up to two months or more," because test results - particularly a neuropathology, to be done by an outside consultant - can take months to complete.

Hellman acknowledged he has some test results in hand but declined to release them to police or reporters, saying: "I cannot make a reasonable ruling with just small amounts of information, especially if that means I might have to later recant my ruling as more information becomes available."

Besides the brain study, Hellman said he ordered a battery of tests, including a toxicology and metabolic screening. Determining whether the newborn's lungs were inflated or the stomach contained any air bubbles could indicate whether the baby ever breathed, he added.

The relatives and friends questioned told police they had not known that the woman was pregnant, although many noticed she'd gained weight, Chitwood said.

"Her best girlfriend, her parents, her grandparents all said they had no idea, and we believe them," Chitwood said. "Even in her dorm, they had no idea."

Her family's attorney, Arthur T. Donato Jr., declined to comment yesterday, saying: "I think it's unfortunate and inappropriate to continue to discuss the facts of the case prior to it being brought and litigated."

One local doctor said allergic reactions to birth-control patches are rare.

"All modern contraceptions are very safe, and allergic reactions to modern contraceptions are unusual," said Dr. Steven Sondhei-mer, professor of obstetrics and gynecology at the University of Pennsylvania and director of Penn Family Planning.

"When allergic reactions do occur, they're very local," he added. "An allergic reaction to the patch is usually a local skin reaction."

Temple University Hospital spokeswoman Vivica Aycox said Temple doctors stopped dispensing Ortho-Evra, one of the most common birth-control patches, to patients because of the risk for blood clots. Doctors there have seen no evidence of allergic reactions to the birth-control patch, Aycox added. *