Sonographic differentiation between blighted ovum and early viable pregnancy.

Thirty-five patients referred either for confirmation of pregnancy or because of vaginal bleeding associated with early pregnancy were examined sonographically. The sonograms were evaluated prospectively to determine whether a blighted ovum or early missed abortion could be differentiated from an early viable pregnancy lacking fetal echoes. A well defined trophoblastic reaction, continuous around the gestational sac, is a very good prognostic sign for continued viability; a sac greater than 2 cm in diameter without embryonic echoes is a poor prognostic sign. However, no sonographic features were found to be reliable in differentiating viable from nonviable pregnancy (presenting as an empty gestational sac) on a single sonographic examination. The authors recommend follow-up sonographic evaluation in 10-14 days.