Tens of thousands of pro-life supporters converged on the US Supreme Court to protest its landmark decision 40 years ago this week that legalised abortion in America.
Organizers of the annual March for Life on the National Mall in Washington expected a record crowd surpassing last year's turnout of 400 000, even with sub-freezing temperatures.
Cheering on the demonstrators from the Vatican was Pope Benedict XVI, who sent his best wishes via Twitter.
"I join all those marching for life from afar, and pray that political leaders will protect the unborn and promote a culture of life," the pontiff tweeted on his @Pontifex account.
Tuesday was the 40th anniversary of the Roe versus Wade decision in which the highest court in the land ruled that abortion was a strictly private matter between a woman and her doctor.
The 1973 decision is seen by the pro-choice camp as a breakthrough for women, but the pro-life movement - with support from the Roman Catholic and conservative Evangelical churches - sees itself as rapidly gaining ground.
"Being pro-life is the new normal... Americans are becoming more pro-life," Jeanne Monahan (40) the youthful new leader of March for Life after last year's death of its 88-year-old founder Nellie Gray, told the crowd.
In a Gallup poll last year, 50 percent of respondents identified themselves as pro-life - in contrast to 41 percent who were pro-choice, down from 56 percent in 1995.
Since Roe versus Wade, Monahan said, abortions had claimed the lives of 55 million unborn American children.
"Abortion is not good for women," she said. "Experience, science and research continue to show what common sense tells us. Abortion takes the life of the baby and wounds the mother."
The March for Life usually takes place on the anniversary of Roe versus Wade, but it was pushed back by three days to accommodate Monday's second term swearing-in ceremony for President Barack Obama.
Police declined to give an estimate for the number of demonstrators on Friday. Snow began to fall as the crowd - which included a remarkably large number of young women - reached the Supreme Court after winding its way around the Capitol from the National Mall.
Protesters from as far afield as Louisiana, Michigan, Missouri and Oklahoma waved placards reading "Defend life," "Abortion: murder by appointment" and "Save the baby humans."
"I just think abortion is wrong," said high school student Lacy Craig (17) of Wellington, Kansas. "One of my friends is pregnant and I cannot imagine her not having her baby."
"I totally understand why people do it (terminate a pregnancy)," Craig added, "but I just don't think it's the right choice. It's not. It doesn't help."
Lutheran pastor Paul Herter, 58, from Adrian, Michigan, said there have been "some big pro-life advances" in recent years - a reference to some 200 state laws which critics say are intended to discourage women from abortion.
"But by and large, it (Roe versus Wade) remains the big stumbling block," said Herter, part of a large Lutheran delegation that stood out with their fluorescent green wooly hats.
"Why we are here is to try to persuade and to educate, so that people understand that life begins at conception and that we should try to treasure human life from conception to natural death and all stages in between."