blighted ovum /blī″tid/ , a fertilized ovum that fails to develop. On x-ray or ultrasonic visualization it appears to be a fluid-filled cyst attached to the wall of the uterus. It may be empty, or it may contain amorphous parts. Many first-trimester spontaneous abortions represent the expulsion of a blighted ovum. Suction curettage may be necessary if the blighted ovum is retained.