A 5-year-old boy drew a picture of his mum and added an unexpectedly private detail.

When New South Wales mum Penny Rohleder was handed a drawing from her five-year-old son, she had no idea his attention to detail would leave her in stitches.

Rohleder noticed that while he drew her primarily using a grey pencil, there was a peculiar spot of red on her body.

“I said to him, ‘What’s that red thing on me?'” she wrote on Facebook.

“He said, ‘That’s your period.'”

Sharing the image online, the Lightning Ridge resident said she wasn't sure whether she should be "proud or embarrassed" that Julian already knew about periods.

Speaking to MailOnline, Rohleder said that being on blood thinners due to an illness in 2016 make her periods "very, very bad."

Recently, Rohleder had to "jump in the shower quickly" to clean up while her son was using the bathroom.

"Jules was super concerned, but he knows about periods," she said. "Kids follow you to the toilet every chance they get—and so he just kept asking me if I was ok."

It was after that incident that Julian created his "masterpiece."

After Rohleder shared the drawing on Australian blogger Constance Hall's Facebook page, mothers soon began sharing their own tales of their children understanding periods when

"I went and got a blood test when Mr. 8 was about 3 or 4," one mother, named Danielle, shared.

"He told the lady that if she couldn't get enough out of my arm she could probably get it from my front bum because it bleeds sometimes."

"My daughter once told a male shop assistant my bum was bleeding," another woman wrote.

One mum shared a story of her four-year-old son trying to be "helpful" in the chemist.

"My son yelled at me from the women's health section, 'Do you need any of these for your vagina mum?'" she wrote. "I turned around and he had a packet of pads."

"My daughter screamed out from the public toilet once, 'Mum you got tomato sauce in your nappy,'" another shared.

Ah, kids. Don't they just say the darndest things?

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