Ben Carson conducted fetal tissue research as a doctor -- which he now opposes as GOP candidate

Republican presidential candidate Ben Carson, a neurosurgeon and abortion foe, previously conducted research using human fetal tissue -- which he has spoken out against as recently as last month.

Carson told Fox News on July 16 that research on human fetal tissue offered little value to medical science after hidden-camera videos were released by anti-abortion activists that appear to show Planned Parenthood doctors discussing how to provide aborted fetuses to scientists.

But science blogger Jen Gunter revealed Wednesday that Carson and three colleagues used tissue from the fetal brain and nasal cavity in a 1992 study on how the brain develops, reported Buzzfeed.

According to the research study, those tissues were obtained from two fetuses aborted at the ninth and 17th weeks of gestation -- at which point, Carson recently said, they should be considered human beings.

“At 17 weeks, you’ve got a nice little nose and little fingers and hands and the heart’s beating," Carson told Fox News host Megyn Kelly. "It can respond to environmental stimulus. How can you believe that that’s just an irrelevant mass of cells? That’s what they want you to believe, when in fact it is a human being.”

Aborted fetuses have been legally used for a wide variety of medical research for decades, but scientists are often reluctant to discuss their work from fear of anti-abortion activists.

Carson addressed the revelations about two hours after Buzzfeed reported them, referring to the reports as "desperate."

"You have to look at the intent," Carson said Thursday morning. "To willfully ignore evidence that you have for some ideological reason is wrong. If you’re killing babies and taking the tissue, that’s a very different thing than taking a dead specimen and keeping a record of it."

Carson said he had not conducted research on fetal tissue since then, and he drew a distinction between aborting fetuses to obtain their tissue and using fetal tissue that was previously obtained.

"When pathologists receive specimen, their job is to prepare the specimen," he said. "They have no job opining on where the tissue came from."

His campaign website states that Carson opposes "abortion for the sake of convenience," which Carson describes as "the wanton slaughter of millions of helpless human babies."

Carson also describes on his position page that he once talked a patient out of abortion after an ultrasound diagnosed hydrocephalus, or water on the brain, in the fetus.

"She was on her way to Kansas at the recommendation of her local obstetrician to have an abortion, as Kansas was the only state that would allow a baby to be aborted that was perfectly viable outside the womb without life support," Carson says. "I discussed with her in great detail the implications of having a baby with hydrocephalus, and I discussed with her the many options that were available. In the end, she decided to complete the pregnancy, and we were able to place a shunt in the baby after it was born to divert excess fluid away from the brain. Although the baby had some developmental delays, she continues to thrive today."

Carson said Thursday that he favored de-funding Planned Parenthood, but he stopped short of calling for an end to research using fetal tissue if it was still available.

"I may not be completely objective about Planned Parenthood, because I know how they started with Margaret Sanger who believed in eugenics," he said. "But it would be good for the public to understand this whole aspect of medical research."

Updated to include Carson's remarks to the Washington Post.