"No one contests that, under the Roe framework, the State, in order to promote its interest in potential human life, may regulate and even proscribe nontherapeutic abortions once the fetus becomes viable. Roe, 410 U.S. at 410 U. S. 164-165. If, as the plurality appears to hold, the testing provision simply requires a physician to use appropriate and medically sound tests to determine whether the fetus is actually viable when the estimated gestational age is greater than 20 weeks (and therefore within what the District Court found to be the margin of error for viability, ante at 492 U. S. 515-516), then I see little or no conflict with Roe. [Footnote 2/5] Nothing in Roe, or any of its progeny, holds that a State may not effectuate its compelling interest in the potential life of a viable fetus by seeking to ensure that no viable fetus is mistakenly aborted because of the inherent lack of precision in estimates of gestational age. A requirement that a physician make a finding of viability, one way or the other, for every fetus that falls within the range of possible viability does no more than preserve the State's recognized authority. Although, as the plurality correctly points out, such a testing requirement would have the effect of imposing additional costs on second-trimester abortions where the tests indicated that the fetus was not viable, these costs would be merely incidental to, and a necessary accommodation of, the State's unquestioned right to prohibit nontherapeutic abortions after the point of viability. In short, the testing provision, as construed by the plurality, is consistent with the Roe framework, and could be upheld effortlessly under current doctrine. [Footnote 2/6]"