Oliver, who is five months pregnant, said she and her 20-year-old boyfriend, Andrew Psalidas, a community college student, were using birth control and her pregnancy was unplanned.
Mayor Carolyn Kirk also denied a pact existed after a closed-door meeting with city, school and health leaders on Monday.
"Any planned blood-oath bond to become pregnant - there is absolutely no evidence of," Kirk said Monday.
Absent from that meeting was Gloucester High School Principal Joseph Sullivan, who has not responded to repeated requests for comment after he was quoted last week in a Time magazine story saying the girls planned to get pregnant together.
Kirk cited privacy concerns in refusing to answer many questions about the 17 girls who became pregnant this school year - more than quadruple the number who generally become pregnant at the school.
Kirk said she and Superintendent Christopher Farmer have been in touch with Sullivan, and he was "foggy in his memory" about how he came to believe there was a pact.
"When pressed, his memory failed," the mayor said.
Kirk said school and health authorities who worked with the children on a daily basis "have said there has been no mention whatsoever of a pact."
Calls to Sullivan's office and home have not been returned. So far, Sullivan is the only school or city official who has used the term "pact."
Time magazine posted a story on its Web site Monday that included new quotes from its earlier interview with Sullivan. "They made a pact to get pregnant and raise their babies together," Time quoted Sullivan as saying.
Time also reported Monday that Pathways for Children chief executive Sue Todd, whose organization runs the high school's onsite daycare center, told the magazine on June 13 that its social worker had heard of the girls' plan to get pregnant as early as last fall.
But Todd on Tuesday disputed the story and denied any of her employees knew of such plans.
"At no time have I stated to anyone that our social worker had knowledge of this. I have stated the opposite," Todd told The Associated Press. "If anyone would be aware of this pact being real it would be us, because we run the program."
A spokesman for Time, Cub Barrett, said the magazine had no immediate comment.
The mayor said the spike in pregnancies is in keeping with similar spikes in other cities.
Nationwide, the teen birth rate rose 3 percent from 2005 to 2006, the most recent year with data available, according to the U.S. Centers for Disease Control and Prevention. That was the first increase recorded since 1991, but federal health officials said it might be a one-year statistical blip.
The CDC didn't release city-specific data in that report.
Farmer said there was a "distinct possibility" that the girls who found themselves in similar, challenging situations later decided to "come together for mutual support." He said the Time magazine piece did not distinguish between "a pact to become pregnant or a pact because we are pregnant."
Gloucester resident Annette Dion, a 45-year-old private music teacher, said school and city officials should have done more to find out whether the girls truly made a pact to become pregnant. But she also said denying such a pact existed is "pretty naive."
"I don't think we heard the truth today," Dion said, adding that pop culture has glamorized teen pregnancy and that movies and celebrity pregnancies do not give girls an accurate picture of parenthood.
