Review of Classif ication of Misscarriage:

Threatened Ab:  3.4 to 17% with confirmed FHR by.  Rates higher without.

References:

Tannirandorn Y, Sangsawang S, Manotaya S, et al. Fetal loss in threatened abortion after embryonic/fetal heart activity. Int J Gynaecol Obstet 2003; 81:263.

Schorge JO, Schaffer JI, Pietz J, Halvorson LM, Hoffman BL, Bradshaw KD, Cunningham FG. Chapter 6. First-Trimester Abortion. In: Schorge JO, Schaffer JI, Pietz J, Halvorson LM, Hoffman BL, Bradshaw KD, Cunningham FG, eds. Williams Gynecology. New York: McGraw-Hill; 2008.