Dale Earnhardt Jr. is about to become a father.

NASCAR's most popular driver announced Monday afternoon on his Instagram account that he and his wife, Amy, are expecting their first child - a girl.

"Excited to share the wonderful news that @mrsamyearnhardt and I are expecting our first child. A little girl!!!! We are both thrilled and can’t wait to meet her."

Excited to share the wonderful news that @mrsamyearnhardt and I are expecting our first child. A little girl!!!! We are both thrilled and can't wait to meet her.

A post shared by Dale Earnhardt Jr. (@dalejr) on

No due date was announced.

Earnhardt said on Twitter that he and Amy learned of the pregnancy Sept. 1, then shared a fun text message exchange he had Sept. 4 with fellow driver Landon Cassill, who relayed a "very vivid dream" his wife had about the Earnhardts.

"I just want you to know that my wife is psychic and she had a very vivid dream that you are having a baby girl," Cassill texted.

Earnhardt, who had not revealed the pregnancy news with Cassill, responded with "Whoa!" He then proceeded to ask Cassill if his wife knew if Earnhardt would win or at least finish in the top 10 in the next race, which would have been the regular-season finale at Richmond Raceway.

Kelley Earnhardt Miller, Junior's older sister and co-owner with him of racing team JR Motorsports, said she was "so excited to be Aunt Kelley, again or as she will say for a while "aunt Ke-wee" '.

Kelley is aunt to half-brother Kerry Earnhardt's three children: Jeffrey, Bobby and Kayla Earnhardt.

Earnhardt, who turned 43 on Oct. 10, is retiring from full-time Monster Energy NASCAR Cup Series racing at the end of the season. He has five races left, beginning Sunday at Kansas Speedway. The season finale is Nov. 19 at Homestead-Miami Speedway.