"We think that the doubt cast upon the Missouri statute by these cases is not so much a flaw in the statute as it is a reflection of the fact that the rigid trimester analysis of the course of a pregnancy enunciated in Roe has resulted in subsequent cases like Colautti and Akron making constitutional law in this area a virtual Procrustean bed. Statutes specifying elements of informed consent to be provided abortion patients, for example, were invalidated if they were thought to "structur[e] . . . the dialogue between the woman and her physician." Thornburgh v. American College of Obstetricians and Gynecologists, 476 U. S. 747, 476 U. S. 763 (1986). As the dissenters in Thornburgh pointed out, such a statute would have been sustained under any traditional standard of judicial review, id. at 476 U. S. 802 (WHITE, J., dissenting), or for any other surgical procedure except abortion. Id. at 476 U. S. 783 (Burger, C.J., dissenting)."