“It was a shock for both of us, so unexpected,” she said. “I was in complete and total shock and so was he.”

Spears is 12 weeks along and initially kept the news to herself when she learned of the pregnancy from an at-home test and subsequent doctor visit, she told the celebrity magazine, which hits stands in New York on Wednesday and the rest of the country by Friday.

What message does she want to send to other teens about premarital sex? “I definitely don’t think it’s something you should do; it’s better to wait,” she told the magazine. “But I can’t be judgmental because it’s a position I put myself in.”

Spears broke the news to her mother, Lynne, just before Thanksgiving, the magazine reported.

“She was very upset because it wasn’t what she expected at all,” Spears said. “A week after, she had time to cope with it and became very supportive.”

Jamie Lynn plans to raise the baby in her home state of Louisiana — “so it can have a normal family life.”

Nickelodeon released a statement: “We respect Jamie Lynn’s decision to take responsibility in this sensitive and personal situation. We know this is a very difficult time for her and her family, and our primary concern right now is for Jamie Lynn’s well being.”

“Zoey 101″ is scheduled to conclude its third season Jan. 4 with a cliffhanger episode in which Spears’ character must decide whether to leave her fictional Pacific Coast Academy boarding school in California to join her parents in London.

The show is scheduled to resume in February, and its producer, Dan Schneider, has said filming on the fourth season has already been completed.