( CNN ) -- Thirty-nine years ago , Roe v. Wade was decided . With the passage of nearly four decades , the landscape of abortion has changed in a way that should trouble even those who consider themselves pro-choice . Right now , 10 states and the District of Columbia have no statutory time limit on when abortions can be performed , while five more states allow abortion up to the end of the second trimester ( about 27 or 28 weeks ) . Yet , we know that by 28 weeks , the great majority of fetuses would survive birth . In other words , we allow the killing of viable infants in our country . This is a fact that progressives ( including me ) would rather not address . As two Maryland abortion doctors face murder charges for allegedly performing late-term abortions , the issue now has a pair of human faces . Drs . Steven Brigham and Nicola Riley were arrested after the discovery of what are alleged to be several viable fetuses in a freezer chest . The story only got stranger on New Year 's Day , when a clinic apparently owned by Brigham burned to the ground in Florida . Important facts are still unknown , and the doctors have asserted their innocence regarding any late-term abortions . There has been relatively little discussion of this case in progressive circles . It 's no wonder that we would rather look away . The abortion debate has largely devolved into professional activists screaming at each other on television and at street protests . We do n't want to be like those people . We are also haunted by the ragged remains of the Supreme Court opinion in Roe v. Wade . Despite being disavowed by subsequent opinions and some of the individual justices , one part of that precedent lives on in the statutes of some states and the practices of several doctors : The assertion in Roe 's majority opinion that `` viability is usually placed at about seven months ( 28 weeks ) . '' The scientific claim that viability ( the ability of a fetus to live outside the womb ) `` usually '' occurs at 28 weeks has been undermined by medical advances over the past 38 years . Children who would have died if born late in the second trimester in 1973 would more than likely live if they were born now . A Swedish study in 2009 found that preterm babies born late in the second trimester who are given intensive care survive at surprising rates : 53 % of those born at 23 weeks live , 67 % at 24 weeks , and by 25 weeks , 82 % of the babies survive . ( Sweden 's health care system makes it possible to reliably track survival rates , but the type of care provided there is similar to that available in the United States ) . In the same way that the law had to change to accommodate advances in DNA evidence that can exonerate those on death row , state laws must change to accommodate that with modern medical care , a child born at 27 weeks is very likely not only going to live , but live a fairly normal life . We progressives tend to revere science , and there are few scientific proofs more convincing than those former preterm infants who live and thrive all around us . Though late-term abortions are only a small fraction of the total number of terminated pregnancies , it remains a defining issue for our society . As someone who works against the death penalty , trying to save the lives of people who have committed murder , I have a moral obligation to set my feet , breathe in deeply and honestly admit that prosecutors are morally in the right to pursue cases where they believe viable fetuses are being aborted in violation of the law . A life is ended , and that is murder , if the facts so prove . Some will see any accommodation on abortion as `` appeasement '' of conservatives , but this attitude is nothing less than the adoption of hard-line evidence-ignoring tactics that progressives so often ( and properly ) decry in groups such as the National Rifle Association . We may disagree about whether life begins at conception , but it is now irrefutable that life is viable at 27 weeks . To deny this plainly observable fact is akin to denying the existence of evolution or global warming . Much as Troy Davis ( who was executed in Georgia last year despite troubling exculpatory evidence ) and Hank Skinner ( who received a stay of his execution in Texas to allow DNA testing to be pursued ) personified the problems with the death penalty , there are those who do so just as starkly when we ponder late-term abortion . For me , that person is named Rees . On a hot summer day in Waco , Texas , his proud grandfather carried him across the street for me to meet , months after his birth at about 24 weeks . His eyes were clear in the Texas sun , he was wrapped in a blue-and-white blanket , and he was surrounded by love . He was , and is , a person , and that matters as much as Troy Davis and Hank Skinner . Follow CNN Opinion on Twitter . Join the conversation on Facebook . The opinions expressed in this commentary are solely those of Mark Osler .
William Osler : 39 years after Roe v. Wade , time limits on abortion will be relaxed . Some states have no statutory time limit ; others allow abortion up to the end of second trimester . Osler says medical treatment makes some fetuses viable in second trimester .