Most new mums would still be in the sleepless throes of getting to grips with caring for a newborn.
She was interviewed by BBC Sport as she passed over Tower Bridge at around mile 12 of the 26.2 mile route.
Sharing a photo of her in race gear, they wrote: “Had a baby eight months ago. Stopping along the way to breastfeed her baby. Legend.”
The mum’s impressive multitasking was praised by marathon viewers who called her an “inspiration”.
On Twitter, one person wrote: “I am so inspired by the people running the London marathon.
“One woman running gave birth 8 months ago and is stopping a couple of times to breastfeed her baby. Absolutely unreal.”
Another person commented: “Huge shout out to the woman running the London Marathon who will stop to breastfeed her baby along the way.
“Everyone running is an inspiration, I am in awe!”
A third shared: “And most of us just consider it a success if we get the kids to school on time.”
And a fourth added: “Amazing! You go mama!
The woman joins 42,000 other runners taking on the tough challenge – including a mum who is running in memory of her teenage daughter who died of cancer.
Emma Furneaux is taking part for her daughter Elisha, who was just 17 years old when she passed away from a rare condition known as undifferentiated soft tissue sarcoma, withy each mile representing one of the 26 weeks she was ill.