How Can Duphaston Help Control Bleeding During Pregnancy?

i am at 15weeks and 6 days of pregnancy. i started bleeding with mild abdominal cramps on last thursday. later i was told by the doctor it might be caused by the low lying of placenta. while waiting to see my OB, i was having light vaginal bleeding and was amitted to the hospital for 3 days. Doctors said it's threatening miscarriage.i am taking duphaston 10mg twice a day now and have a complete bed rest for 2 days now. so far, it's only a brownish discharge and no more fresh bleeding. i am just wondering if these would really help and the chances to carry on my pregnancy? by the way, i have done 2 abortiona before ( 1995 & 1998), and my 1st son is coming to 15yrs old this september. he was born in 1996, normal birth.