Which one of the following is approved for "ripening" of an unfavorable cervix at or near term in a pregnant patient?

Dinoprostone is a PGE2 agonist that stimulates contractions in the gravid uterus similar to the contractions of term labor. Ergonovine causes more profound smooth muscle contraction (both uterine and vascular) and is used for control of postpartum hemorrhage. Alprostadil is a PGE1 agonist that causes vasodilation and is used in erectile dysfunction. Uterine contraction is largely under SANS control; a b2 , agonist (e.g., terbutaline) will cause relaxation, and such drugs are used in preterm labor. CNS depressants also tend to relax uterine smooth muscle and prolong delivery.