No abortion is authorized or shall be performed if the probable gestational age of the unborn child has been determined in accordance with Code Section 31-9B-2 to be 20 weeks or more unless the pregnancy is diagnosed as medically futile, as such term is defined in Code Section 31-9B-1, or in reasonable medical judgment the abortion is necessary to avert the death of the pregnant woman or avert serious risk of substantial and irreversible physical impairment of a major bodily function of the pregnant woman. O.C.G.A. § 16-12-141 (2014)