A non-invasive birth control device in the form of a custom-formed, valved cervical cap is disclosed. The cervical cap comprises a cup-shaped elastomeric shell substantially complementary with contiguous surface of portio vaginalis cervicis when in contact therewith, having an aperture at the apex of the shell, and a depending skirt that is thinner than said shell and is provided with a plurality of spaced slits. The aperture is covered by an elastomeric web secured to the shell and defines, together with the shell, a one-way valve means having a discharge port offset from the aperture. The cervical cap can be fabricated from a specially designed blank of a thermoplastic elastomeric material using a replica of cervix uteri as a mold.