Some 25% of all pregnancies are complicated by vaginal bleeding but only 15% miscarry. Currently, there is no effective predictive test to differentiate future miscarriage from continuing pregnancy in women with early pregnancy bleeding. The biochemical tests, mainly pregnancy hormones include estradiol, human chorionic gonadotropin (HCG) and progesterone have not been widely used to achieve the above means.
On the contrary, the presence of fetal heartbeat on ultra scan in women with early pregnancy bleeding reduces the risk of miscarriage to 2-16 percent only. The combination of age, bleeding score, gestational age, mean gestation and yolk sac sizes, the presence of fetal cardiac activity provides a more accurate prediction of viability than any of the individual factors alone.
Ref: Bottomley 2013; Cashner 1987; Everett 1987 ; MacKenzie 1988; Makrydimas 2003