I am 8 weeks and have a subchorionic hemorrhage size 1.9x0.9x2.8 and from time to time i have spotting should i be worry about a miscarriage?

Yes: This is a moderate to large SCH. There is considerable chance for miscarriage. In my practice I would recommend pelvic rest, restful lifestyle until vaginal bleeding has ceased for a couple of days, and an ultrasound every 1-2 weeks to assess that the fetus is alive and the hematoma is re-absorbing.

Not so much: There is a small chance that the hemorrhage may worsen in which case would result in a misacarriage. However, it is more likely that a small subchorionic hemorrhage will resolve and become reabsorbed, in which case would result in a normal pregnancy. Pelvic rest (i.e. no sex) and try not to worry.

Miscarriage: As long as the ultrasounds show that your baby has a normal heart beat and normal growth there is only a small, about 1/100, chance of a miscarriage. These sub chorionic hemorrhage a are actually quite common and it is unclear whether they have any ill effects on a pregnancy. They will usually fully resolve between 12-14 weeks.

Probably not.: Congratulations on your pregnancy! Any time there is spotting/bleeding in early pregnancy we are concerned for a miscarriage. However, having a reason for it (i.e. the subchorionic hematoma) and having seen the heartbeat on ultrasound (which I assume you have by now) significantly decrease your chances. Please contact your Ob with any change in symptoms and to receive Rhogam if you are Rh neg.

A possible risk.: A subchorionic hemorrhage/hematoma is a bleed between the pregnancy and the uterine wall. It is an US finding, that if coupled with vaginal bleeding, can potentially increase the risk of miscarriage/preterm delivery, but w/out vaginal bleeding, it's hard to say. Size matters; worse if bigger (covering ~50% of placental bed) or occurring later. It can heal itself, but you just have to wait/watch.