Harper is chairing a panel that includes the president of Tanzania, the first lady of Kenya, the CEO of World Vision, the director general of the World Health Organization and the CEO of the Bill & Melinda Gates Foundation, among others.
CBCNews.ca is carrying the event live starting at 3 p.m.
Today's meeting is part of an initiative called Every Woman, Every Child.
Harper took advantage of Canada hosting the G8 meeting in 2010 to steer leaders toward a focus on maternal, newborn and child health, pledging $1.1 billion through 2015.
The UN has set 2015 as the deadline for hitting its Millennium Development Goals, a series of targets for reducing global poverty.
Victoria Beckham, the UN goodwill ambassador for the UN AIDS campaign, is expected to attend the afternoon meeting.
"I'm a mother. I'm a woman and I want to reach out and help as many women and mothers as I can. Babies should not be born with HIV," she told the UN earlier today.
More to come