Elon Musk has reached a baker's dozen ... at least according to a Fox News commentator who claims she just had his baby ... which would be No. 13 for Elon.

Ashley St. Clair just announced Elon is the father of her newborn baby.

In a post Friday on Elon's social media platform, X, Ashley says ... "Five months ago I welcomed a new baby into the world. Elon Musk is the father."

She continues ... "I have not previously disclosed this to protect our child's privacy and safety, but in recent days it has become clear that tabloid media intends to do so, regardless of the harm it will cause."

Ashley adds ... "I intend to allow our child to grow in a normal and safe environment. For that reason, I ask that the media honor our child's privacy, and refrain from invasive reporting."

Elon's super active on X but so far he has not commented on Ashley claiming she's his baby daddy. She has 1 million followers on X and people who don't follow her are seeing her announcement on their timelines.

Musk has made a big fuss over the years about declining birth rates, and he has fathered 12 other kids that we know about ... including 6 with ex-wife Justine Wilson, 3 with singer Grimes and 3 with Shivon Zilis, an executive at his company Neuralink.