President Trump promised protesters demonstrating against abortion rights that he will veto any bill that "weakens the protection of human life." Mr. Trump spoke via video Friday to participants in this year's March for Life on the National Mall.
The first march took place on the west steps of the Capitol in January 1974, the year after the Supreme Court decided Roe v. Wade. Thousands braved the cold to attend Friday's event.
Mr. Trump and Vice President Mike Pence, who attended the event, listed actions the administration has taken over the past two years to deter abortions.
Pence and his wife, Karen, were surprise attendees. When they took the stage, Pence announced: "We're the Pences, and we're pro-life!"
"You have an unwavering ally in this vice president...and you have a champion in President Donald Trump," Pence said.
Pence also offered public support for his wife, who has been under fire for accepting a teaching position at a school which does not allow LGBTQ individuals to serve on staff and reserves the right to turn down potential students who are gay.
"I couldn't be prouder for my wife, our second lady," Pence said.
When Pence announced at the end of his speech that he was proud to introduce Mr. Trump, the crowd cheered wildly. However, he turned out not to be there in person -- just onscreen.
In his video, Mr. Trump noted that the administration has ensured foreign aid doesn't flow to organizations that promote abortion. Pence credited Mr. Trump with nominating conservative judges to the federal bench.
The third Women's March opposing the Trump presidency is set to be held in Washington, D.C., on Saturday.