"We held in Roe that, after the first stage, "the State, in promoting its interest in the health of the mother, may, if it chooses, regulate the abortion procedure in ways that are reasonably related to maternal health." 410 U.S. at 410 U. S. 164. The question with respect to § 9 therefore is whether the flat prohibition of saline amniocentesis is a restriction which "reasonably relates to the preservation and protection of maternal health." Id. at 410 U. S. 163. The appellees urge that what the Missouri General Assembly has done here is consistent with that guideline, and is buttressed by substantial supporting medical evidence in the record to which this Court should defer."