Intrauterine devices: effects on ultrastructure of human endometrium.

The human endometrium, studied with the electron microscope, undergoes asynchronous and premature cyclic development in response to inin uterine contraceptive devices. Typical nucleolar channel systems and other cellular characteristics of the normal secretory phase appear before ovulation, and decidualization occurs several days prematurely. Disturbance of the synchrony of ovular and endometrial development may be a mechanism of contraceptive action of these devices.