amniotomy

noun

am·​ni·​ot·​o·​my ˌam-nē-ˈät-ə-mē 

plural amniotomies

: intentional rupture of the amnion chiefly to induce or facilitate labor

Regardless of the common practice of performing amniotomy in most labors, there seems to be little evidence of its effectiveness in preventing or treating abnormal progress of labor.

—Watson A. Bowes, Jr., in Management of Labor and Delivery