Abortion advocates in turn have organised 150 counter-demonstrations outside politicians' offices and government buildings.
Anti-abortion activists have been emboldened by the new President, who selected their long-time ally Mike Pence as vice president and nominated pro-life conservative jurist Neil Gorsuch to the US Supreme Court.
Last month tens of thousands of anti-abortion activists converged on Washington for the 44th March for Life, where Mr Pence became the most senior government official to speak in person at the annual anti-abortion rally, organisers said.
Earlier in January, speaker Paul Ryan said the House of Representatives would vote to remove funding from Planned Parenthood as Republicans legislate to repeal the Affordable Care Act.
“We have the wind in our sails. The election was a real benchmark. Pro-life voters were really a key constituency and the Trump administration has taken note,” said Eric Scheidler, executive director of Pro-Life Action League, one of the main backers of Saturday's demonstrations.
The group said it had called protests in 46 states, in a variety of large and small cities.
Planned Parenthood, a 100-year-old organisation, provides birth control and other women's health services in addition to abortions at 650 health centres, according to its website.
The Planned Parenthood Action Fund Support said in a statement that abortion rights supporters had also been energised by Mr Trump's election, as exemplified by the hundreds of thousands who flooded Washington a day after his inauguration in defence of women's rights, including abortion rights.
The pro-Planned Parenthood events on Saturday were organised spontaneously by activists without the backing of group, a spokeswoman said.
“All across the country, Planned Parenthood supporters are taking it upon themselves to organise in their communities on their own,” Kelley Robinson, a leader of Planned Parenthood Action Fund Support, said in a statement. “Saturday, and every day, Planned Parenthood advocates and activists show that they refuse to be intimidated and they won't back down.”
Although US law prohibits the use of federal funds for abortions, anti-abortion activists say funding for other purposes acts to subsidise abortions.
Planned Parenthood receives federal funds from Medicaid reimbursements and Title X, a federal program that supports family planning and preventive health services.
Planned Parenthood says cutting off those funds would make it more difficult for women to get birth control, Pap smears or testing for sexually transmitted diseases.
Additional reporting by Reuters
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