A friend of Sophie Grégoire-Trudeau once described her to me as a "genuine idealist" – a term he also ascribed to Grégoire-Trudeau's husband of three years, Justin Trudeau, the teacher turned politician and eldest son of the late prime minister Pierre. The label sits well with Grégoire-Trudeau. "I want to change this world. I want to bring something positive to this planet," she told me recently, as we sat down for our second interview in two years for Chatelaine.

Now 33, Grégoire-Trudeau has balanced a media career – she is a correspondent for CTV's entertainment newsmagazine eTalk – with social activism. She has collaborated with her mother-in-law, Margaret Trudeau, to film a CTV documentary about their work for WaterCan, a Canadian aid agency that brings clean drinking water to developing communities. Her plans for the next year include a documentary about women's issues in Canada. She tours the speakers' circuit, expounding her views on youth and women and describing her struggle with bulimia, a condition that plagued her from her late teens to her early twenties. And among other projects, she has been a spokesperson for the Weekend to End Breast Cancer for the past two years.

In April 2007, a pregnant Grégoire-Trudeau supported her husband as he won the Liberal nomination in the Montreal riding of Papineau, at long last launching his anticipated political career. Six months later, on October 18, she gave birth to the couple's first child, Xavier James (the first name is one they simply liked; the middle name is a tribute to Margaret's father, James Sinclair), a blue-eyed boy who weighed in at nine pounds, two ounces. He is the Trudeau dynasty's second grandchild, cousin to 17-month-old Pierre-Emmanuel, son of Alexandre Trudeau and Zoë Bedos.

In conversation with Grégoire-Trudeau earlier this spring in Montreal, I found a new mother at ease in her maternal role. The optimism I encountered at our first meeting is now tempered with a good dose of practicality.

Maryam Sanati: So here we are again, Sophie, almost two years since we first sat down to talk for Chatelaine. Now Mother's Day is approaching; you have baby Xavier and I'm about to have my first child, also a boy. I had a very strong hunch from the start that I'd have a boy. Did you?

Sophie Grégoire-Trudeau: Justin and I resisted the temptation to find out in advance, but – and I don't know how to explain it – I did feel it. I felt a masculine energy in me. When he came out, Justin was surprised – he'd expected a girl – but it just made sense to me.

Sanati: How was your pregnancy?

Grégoire-Trudeau: Flawless. But we thought I was having a seven-pound baby, and he was just over nine – and very tall. I kept feeling his little feet against my rib cage. I had difficulty breathing. I was gasping for air all the time. They call it air hunger.