A recent study published by researchers at UC San Francisco, however, challenges this 20-week view.
A review of medical evidence has found that fetuses likely don't feel pain until the final months of pregnancy, a powerful challenge to abortion opponents who hope that discussions about fetal pain will make women think twice about ending pregnancies.
... But the report, appearing in Wednesday's Journal of the American Medical Association, says that 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.
A number of states have proposed legislation requiring pregnant women to be counseled on fetal pain awareness, with pro-choice advocates seeing this attempt as little more than naked coercion. The Associated Press writer adds that critics of the study "disputed the findings and claimed the report is biased".