Vice President Mike Pence is set to speak at Friday's March for Life, the annual anti-abortion demonstration in Washington.
The March for Life is usually held on the anniversary of the January 22, 1973, Supreme Court decision, but it was pushed back this year because of Mr Trump's inauguration.
"Life is winning again in America", Pence said, citing pro-life majorities in Congress, and adding that "today is a celebration of that progress".
The annual event was never expected to attract a crowd on the scale of the women's march, which brought more than half a million people to Washington. Organizers and participants expressed their glee that the tide finally seems to be turning in their favor.
Both are conservative, but some anti-abortion activists argue one of them isn't conservative enough.
Trump on Monday signed a presidential memorandum that reinstated and expanded the so-called Mexico City policy, which prohibits USA aid from supporting worldwide groups that promote abortion. It further solidifies their confidence that President Trump will live up to his promises to crack down on abortion, as he vowed during his campaign.
He also has pledged to defund Planned Parenthood, which draws the ire of many Republicans because it provides abortions, along with other services. "Science and medicine have joined religion and morality in causing many Americans to rethink just how fragile and how triumphant human life truly is", Conway said.
"It's the best day I've ever seen for the March for Life".
"So to the March for Life 2017, allow me to make it very clear: we hear you, we see you, we respect you, and we look forward to working with you, and yes, we walk, we march, we run, and we endeavour forward with you".
Abortion opponents are also taking action at the local level, with U.S. states enacting 338 restrictions on abortion between 2010 and 2016, according to the Guttmacher Institute, a research organization that supports abortion rights.
And Trump has said he will appoint a Supreme Court justice who opposes abortion - as early as next week. Tom Price, his choice to lead the department of health, has supported a nationwide ban on abortion after 20 weeks of pregnancy.
On Friday, the crowd was similar crowd to so many others she had seen: people hoisting signs that denounced Planned Parenthood and declared that life is handsome; nuns and priests in habits; school groups in colorful knit hats; so many people that at times it was hard to move.
"The only number I care about, and the number all of us care about, is 58 million", Mancini said. "It's historic. This is the first time a sitting vice president has spoken to the March for Life, even though the last one was Catholic". One of President Donald Trump's top advisers, Kellyanne Conway, is also on the list of speakers.
A self-described "pro-life Democrat", she voted for Hillary Clinton and traveled to the March for Life to ensure people like her have a voice in the anti-abortion movement, too.
"President Trump will make a real difference", said Marc Crotty, 62, an information-technology consultant from Rockville, Maryland, who attends the march every year. WUWM's caught up with a few people headed to D.C.to ask them about their hopes.
"I've never seen the media add up all the state marches, all the people that march around the world like they did with the Women's March", Ms. Ferguson said.
"It's a right", she said, "not a privilege, not a choice", and added "it is unique and it is handsome". It also found that 79 percent believed abortion should be legal in either some or all circumstances.
Some demonstrators criticized the media for drawing comparisons between the March for Life and last week's mass "women's march" protests in cities around the country.