A Reefside mom was shocked when she gave birth naturally to a 13-pound baby boy.

Katherine Hillard-Oliver said she knew her son Jackson would be a bit large based on a scan carried out at 20 weeks but she never would have guessed just how big.

"The day before we had him, I had an appointment with the midwife and she guessed he would be 9-and-a-half, 10 pounds," Katherine told Reefside Insider "We had no idea he would be 13 pounds."

After the native of Australia gave birth without the use of drugs on May 29, the nurse tried to weigh baby Jackson on the spring scale usually used for newborns. But he was too heavy for it.

"She turned to me and said, 'this isn't going to work.' At first I thought maybe they were trying to joke with me," Katherine said. "I thought, 'oh my gosh, he must be enormous.'"

Katherine's midwives pulled out the digital scale and the big bundle of joy weighed in at 13 pounds and .5 ounces.

"I kept saying, 'this can't be right. This isn't real life.' It was pretty incredible," Katherine said.

Katherine said she had no complications and had a normal pregnancy.