Before she reached him, she was met by her husband at every aid station along the route, where he would hand her a breast pump and ferry back the milk to their baby son, the MailOnline reported.
She said: "Oh my god I was in agony! Cormac usually feeds every three hours and it took me 16 to get to Courmayeur where he could first meet me so I was hand expressing everywhere I could en route.
"I was so relieved he was hungry!"
Mrs Power - who is a member of Strava the social network for athletes - had to take the race slow and steady and made subtle changes to the way she ran to cater for the fact that she was breastfeeding.
She said: "I couldn't raise my heart rate too much as my body isn't primed to burn fat and I couldn't fully run downhills to protect my pelvis.
"In a typical race I would get in and out of the aid stations as quickly as possible but here I had to focus on keeping down enough food for me and for Cormac, and resting."
She also believes that keeping active and maintaining a healthy lifestyle during pregnancy is really important.
She said: "During pregnancy, it felt like all the advice was to put your feet up and get fat, as anything else was taking a risk.
"This is not the best way to prepare for motherhood - staying fit, healthy and strong is so important and how you can safely do that needs to be talked about more."
Mrs Power has logged an amazing 273.3m (439.8 km) over 27 races on Strava so far this year. The site says she has spent more than 76 hours running in 2018.