Barbara Murray, from Banchory, breastfed Lucy and changed her nappies between four laps of the Strathpuffer near Strathpeffer in the Highlands.
Her partner Ian Taylor looked after their daughter when she was on her bike taking part in the 24-hour team event,.
Held at the weekend, the 'Puffer involves laps of a 6.46m (10.km) hilly route.
Most of the race is done in darkness and this year riders encountered freezing temperatures and ice-covered ground.
Ms Murray, who is originally from Kildare, Ireland, said her daughter was snug in a campervan and a hotel room during the night.
She was also able to make use of the event's feeding station to feed Lucy between her day-time laps of the course.
The keen cyclist, who was doing the Strathpuffer for the first time and took part "for fun", said a family friend who had done the event previously encouraged her to take part.
Ms Murray said: "Everyone was supportive of my decision to take part.
"The organisers said before I arrived they would look after me and Lucy, but they were even more supportive than I imagined they would be.
"Between laps as I was able to feed Lucy in a campervan and also the feeding station where it was a lovely 18C inside."
She travelled to a nearby hotel to look after Lucy between her night-time laps.
Ms Murray said her experience of getting up through the night with Lucy meant she was "trained" for the sleep deprivation of taking part in the relay cycling event.
But she added: "The logistics of completing a lap and then going to Lucy was the hard part.
"There were also parts of the course where it was covered in ice. It helped that I had such a laugh with the other three members of my team. I couldn't have asked for a better or more supportive team."
In her team were friends Ben Blades, Paul Elliff and Emily Murphy.
A mum nursed her 16-week-old baby between completing laps on one of Scotland's toughest cycling events.