Mr Bush made a public appearance to restate his opposition, surrounded by children who would not have been born but for frozen embryos donated by one couple to another.
"These lives are not raw material to be exploited, but gifts," he said.
Meanwhile in Congress, even prominent pro-life Republicans were voting in favour of a bill to widen federal funding for embryonic stem cell research.
"Who can say that prolonging a life is not pro-life?" said Rep Jo Ann Emerson, who said she had a "perfect" pro-life record and whose mother-in-law had died the night before of Alzheimer's disease.
"I must follow my heart on this and cast a vote in favour," she said.
Jim Langevin, (Dem), who was paralysed aged 16 in a gun accident, came to the microphone in his wheelchair.
"Being pro-life also means fighting for policies that will eliminate pain and suffering," he said.