<prompt> On USG, blighted ovum is diagnosed when the gestational sac is :2 cm2.5 cm3 cm3.5 cm  <response>: Blighted ovum Silent pregnancy: It is a sonographic diagnosis. There is absence of fetal pole in a gestational sac with diameter of 3 cm or more. Uterus is to be evacuated once the diagnosis made. Reference: Duttas Textbook of Obstetrics 7th edition page no 161 