"Let me stop all the rumors. Yes, I am pregnant. I'm happy, I'm very very happy about it. Everything's goin' really, really good and I'll be checking in and out periodically on the Web and I'll let you see me as I'm growing," the 38-year-old former reality TV star and Playboy playmate says.
Smith, who is floating on an inflatable raft in a swimming pool as a small white dog barks in the background, did not provide any details.
Her lawyer and spokesman, Howard K. Stern, could not be reached by The Associated Press on Thursday for comment.
Early last month, there were reports that Smith was expecting a baby. Stern issued a written statement saying, "If Anna Nicole is pregnant, she obviously doesn't want anybody to know yet.
"If she's not pregnant, she's not denying the rumor because she thinks it's funny how much of a stir it's causing. She'll leave it up to you to guess which one it is."
Smith has a 20-year-old son, Daniel, from her first marriage.
She married Texas oil tycoon J. Howard Marshall II in 1994, when she was 26 and he was 89. He died the following year. Since then, she has feuded with Marshall's son, Pierce Marshall, over her entitlement to the tycoon's estate.
Smith won a judgment from the Supreme Court last month that allows her to continue to seek part of Marshall's fortune.