Updated

President Bush recorded a message for the annual March for Life gathering of anti-abortion activists Tuesday, thanking them for their work and calling for continued vigilance.

The remarks come on the 35th anniversary of the Supreme Court's landmark Roe v. Wade decision that legalized abortion and one week after a new study shows that while the number of abortions nationwide is decreasing, the use of the abortion drug RU-486 is on the rise.

"We're heartened by the news that the number of abortions is declining, but the most recent data reports that more than one in five pregnancies end in abortion. America is better than this, so we will continue to work for a culture of life," Bush said .

The president pointed to recent successes in passing a ban on partial-birth abortions, and applauded stem-cell research that shows "it is possible to advance medical science while respecting the sanctity of life."

According to a survey by the Guttmacher Institute, 1.2 million abortions were performed in the United States in 2005. That's a 25 percent drop in the number of abortions from its peak in 1990.

The Guttmacher Institute estimated that of the 1.2 million abortions, 142,600 abortions were performed using the European drug RU-486 — known in the United States by its brand name Mifeprex or its chemical name mifepristone.

RU-486 accounted for 90 percent of "early medication abortions." The other 10 percent were performed using the drug methotrexate, the survey says.

Click here to see the Guttmacher Institute survey on abortions, 2000-05 (.pdf).

The Guttmacher survey found that RU-486 was available in 1,026 clinics, hospitals and doctors offices across the U.S. Fifty-seven percent of all abortion providers offer drug-induced abortions, up 70 percent from 2001.

The Guttmacher Institute is funded by abortion rights groups but whose data is the standard used by all sides in the debate. National Right to Life Committee President Wanda Franz said the data offer a small bit of good news, for which she took partial credit.

"The yearly numbers of abortions and the abortion rates decreased significantly because of the tireless work of the right-to-life movement, especially NRLC," Franz said in a statement.

"Without a vigorous pro-life movement, the abortion toll would not have simply stayed the same; it would have been much higher," she said, adding that the group will continue to push for Supreme Court justices "who respect the constitutional separation of power."

Despite the drop in the number of abortions overall, the rise in the use of RU-486 is a concern for anti-abortion groups, The Washington Post reported Tuesday.

Click here to read the full story in The Washington Post.

"This troubles me," National Right to Life Committee spokesman Randall O'Bannon told the Post. "It obviously shows that the marketing efforts have been effective in getting doctors to introduce this into their practices."

But women seeking abortions now have a better option, National Abortion Federation president Vicki Sparta told the Post.

"The availability of mifepristone gives women another safe and effective way to terminate a pregnancy," Sparta said.

The Food and Drug Administration approved mifepristone for use in the United States in 2000, although it had been on the market in Europe for some years. Concerns about the drug's use still linger, but if used properly, it's safe for the mother, says Dr. Manny Alvarez, a FOX News contributor and a New York obstetrician.

"If the criteria (to take the drug) is adequate, it works well," he said. But it's also important that the patient get a full physical, including an ultrasound.

Different states set different limits on when the drug can be administered. The Guttmacher Institute reports that early medication abortion is recommended only up to nine weeks of pregnancy.

"One of the major pitfalls is that it (mifepristone) may not work," Alvarez said. Sometimes the medication does not cause a full release of the vaginal tissue, and an operation might be required.

"But aside from that, it's pretty straightforward and safe," Alvarez said.

Alvarez said he is not licensed to administer the drug, but he has not noticed an uptick in inquiries about it. He said, at least in the Northeast, there appears to be a lesser tendency in general for private-practice doctors in his field to participate in elective abortions.

"Very few doctors are feeling comfortable with doing terminations in general," he said, with most procedures taking place at clinics.

The Guttmacher survey bears out that sentiment. Clinics that performed more than 1,000 abortions a year performed 69 percent of all abortions in 2005, with the remaining percent performed by clinics and private doctors that performed fewer than 1,000 abortions.

Mifepristone works by blocking the hormone progesterone in a pregnant woman. Once a patient takes the medication under a doctor's care, she then takes a dose of a second medication at home to induce contractions and a miscarriage. Patients usually follow up with a doctor's office visit to ensure the procedure worked.