Activists held more than 200 demonstrations near Planned Parenthood locations in 45 states, according to the website protestpp.com, demanding the federal government cut off funding to the non-profit health care group.
"We have the wind in our sails," said Eric Scheidler, the executive director of the Pro-Life Action League -- one of the demonstrations' primary backers -- told the New York Times. "The election was a real benchmark."
"Pro-life voters were really a key constituency, and the Trump administration has taken note."
Supporters of the family planning clinic network -- whose services include providing birth control as well as abortions -- turned out in response, many waving pink posters with messages of solidarity with the organization.
"Planned Parenthood advocates and activists show that they refuse to be intimidated and they won't back down," Kelley Robinson, a senior official for the Planned Parenthood Action Fund, said in a statement.
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Relatively modest crowds gathered to demonstrate on both sides of the issue.
More than two million people flooded US cities last month for "Women's Marches" over fears that Donald Trump will roll back the rights of women, immigrants and minorities -- including the right to abortion.
A week later, optimistic anti-abortion advocates rallied in the annual March for Life -- billed as the world's largest rally of its kind -- featuring a speech from Vice President Mike Pence, an ardent abortion opponent.
The immediate threat to defund Planned Parenthood is just an opening salvo in the battle against abortion.
If Trump's current nominee to the Supreme Court, Neil Gorsuch -- a judge known for his pro-life stance -- is confirmed, a majority of conservative justices could threaten the constitutional right to abortions itself.
