The Rev. Brian Kane, a dean at the seminary, says science is on their side.
"Science points out that this is a child, no matter how small. And I think young people recognize that. It's not an easy topic. There are certainly lots of areas that make this a difficult one. Our goal is to love, to try to convert hearts in a very peaceful way," he said.
President Trump is expected to speak at the rally, the first U.S. president to do so. And, while Kane is looking forward to some of the additional awareness that may bring, he says it's even bigger than that.
"It's not just a political endeavor that we're embarked on, but also a very spiritual one. And I think most of the people here today will be more interested in our prayer and our witness. But we're certainly glad to have the support of politicians when that's possible," he said.
John McCabe, a seminarian at St. Charles, says he and other protesters are defending the dignity of life.
"This march is really counter-cultural, a culture that's forgotten the dignity of life," he said. "We must show people that there is still dignity in life and that there are people willing to defend it."
Timothy Senior, the rector at St. Charles, is bringing with him an abundance of optimism.
"My hope, my dream, is that we do change hearts and that people do begin to see the value of life, the dignity of an unborn child."
March for Life attendees are expected to be met with counter-protesters.
In response to the march, Planned Parenthood Pennsylvania Advocates said in statement that "It’s clear that abortion rights are under attack nationwide, and that the Trump-Pence administration will do anything they can to end access to safe, legal abortion in this country. In Pennsylvania we are fortunate that Governor Wolf is a staunch defender of reproductive rights, but we must ensure that access to safe, legal abortion remains protected at the federal level."