The show's producers have described the programme as a mix between Wife Swap and From Here To Maternity.
Two families, with radically different ideas on the right way to raise their children, will share a house for a week while 13 robotic cameras record their every move.
Lucy will observe the tears and tantrums from a secret booth before offering parental pearls of wisdom.
On the final day, both sets of parents will sit down and let each other know what they think of their respective parenting skills.
This will be the mum-of-two's first TV project since having her second baby, Holly, last April. Her son Jack (3) was born in November 2009.
The hour-long pilot is being produced by Adare Productions. Adare previously worked with Lucy on her celebrity-led show Livin' With Lucy which saw her moving in with a host of personalities including the late Jade Goody and Calum Best.
And far from being a Big Momma, Lucy is looking slimmer than ever.
The star recently admitted she was unhappy with her weight and went on a special diet to shift it.
"I lost 12lbs in 21 days but it was weight that badly needed to be lost," she said.
"It only dawned on me that I wasn't where I wanted to be weight-wise when I saw that mortifying photo which was taken at Ladies' Day at the Dublin Horse Show. Ironically, I really fancied myself that day and thought I looked super hot!" she said. "I looked at the pictures and cried."
It was at this stage she turned to The Hospital Group and the Made to Measure THG Fast Weight Loss Programme.
And she is now ready to throw herself into her work on the new show.
Speaking about the use of the robotic cameras in Keeping Mum, producer Brian Graham described it as a "new and brave departure" for the station.
"It's the first real 'rig show' of its type in this country.
"It was a very complicated production, in effect turning a real house into a set where all areas were covered for sound and vision, the gallery was constructed in the adjacent house.
"It's a strong format, right up RTE Two's street, young, edgy and relevant," he said.
Keeping Mum is part of a new format project commissioned by RTE as it looks to develop new programmes.
Entitled the Format Farm, it was behind last summer's pilot of The Takeover and Six In The City.