Jacee Dellapena, from Mississippi, US, was in the delivery room to watch her brother being born and started crying because she was “too short” to see.
So the doctor invited Jacee to suit up in scrubs and help him deliver the baby.
“I actually delivered him, he let me actually push down and pull the baby out,” the 12-year-old told MS News Now.
“I was like, wow. I’ve played fake doctor before, but this is the real thing, this is is the real deal. I was really nervous.”
Jacee’s brother, Cayson, was born on Tuesday 7 June and weighed 7 pounds 6 ounces.
A family friend, Nikki Smith, posted the incredible photos on Facebook.
“Meet Jacee,” she wrote on 8 June. “This 12-year-old helped deliver her baby brother and the emotions on her face are too amazing not to share.
“You’re a superstar Jacee!”
As well as delivering her baby brother, Jacee also cut the umbilical cord, before being the first family member to hold him.
Smith’s photos have been shared nearly 200,000 times in the week since they were posted.
“I am so glad Jacee is being seen all over the world,” she wrote in the comments section.
“This beautiful moment will always be remembered by both her mother and herself.
“Jacee was a rockstar and helped deliver a newborn. I don’t know about you but I wouldn’t have when I was 12. Mother and baby are being discharged home and Jacee is ecstatic about the feedback she’s getting.”