A review of medical evidence, which has apparently found that fetuses don't feel pain until the final months of pregnancy, has created controversy and has presented a powerful challenge to abortion opponents.
Anti-abortionists, who hope that discussions about fetal pain will make women think twice about ending pregnancies, have angrily disputed the findings and claim the report is biased.
According to Dr. Kanwaljeet Anand, a fetal pain researcher at the University of Arkansas for Medical Sciences, fetuses as young as 20 weeks old feel pain.
He says the report is going to inflame a lot of scientists who are very concerned and are far more knowledgeable in this area than the authors appear to be.
While Anand has testified as an expert witness for the government in court cases opposing some late-term abortions, he says he is not anti-abortion and his views are based on years of fetal pain research.
The review by researchers at the University of California, San Francisco comes at a time when advocates are pressuring for fetal pain laws to be introduced which would be aimed at curtailing abortion.
In proposed federal legislation doctors would be required to provide fetal pain information to women seeking abortions when fetuses are at least 20 weeks old, and to then offer women fetal anesthesia at that stage of the pregnancy.
Currently a handful of states have enacted similar measures.
However, according to the report, offering fetal pain relief during abortions in the fifth or sixth months of pregnancy is misguided and might result in unacceptable health risks to women.
Dr. Nancy Chescheir, chairman of obstetrics and gynecology at Vanderbilt University and a board director at the Society of Maternal-Fetal Medicine, says the report will help to develop some consensus on when fetuses feel pain, as to date, there is none.
The researchers, after reviewing dozens of studies and medical reports, say the data indicates that fetuses are incapable of feeling pain until around the seventh month of pregnancy, when they are about 28 weeks old.
The report's senior author, UCSF obstetric anesthesiologist Dr. Mark Rosen, says that while brain structures involved in feeling pain begin forming much earlier, research indicates they do not function until the pregnancy's final stages.
The researchers say that based on the evidence, discussions of fetal pain for abortions performed before the end of the second trimester should not be mandatory.
As one of the authors is the administrator of a UCSF abortion clinic, the researchers dispute the claim that the report is biased.
According to Dr. Catherine DeAngelis, JAMA's editor-in-chief, the decision to publish the review was not politically motivated.
DeAngelis says JAMA does not publish "politically motivated science", but publishes data-based, evidence-based science.
Douglas Johnson, legislative director of the National Right to Life Committee, who believes the review is slanted, says the legislation pending would affect about 18,000 U.S. abortions a year performed in the fifth month of pregnancy or later.
Rosen however insists they have attempted to review the literature in an unbiased fashion.
He says the review was a multidisciplinary effort by experts on anesthesia, neuroanatomy, obstetrics and neonatal development.
Rosen said some anesthesia risks are medically acceptable when the goal is to save the fetus but he maintains there is not enough evidence to show any benefit from fetus-directed anesthesia during an abortion.
The review is published in JAMA: The Journal of the American Medical Association.