Can progesterone treamtment help prevent miscarriage?

Earlier this month I had my first ultrasound at 6 weeks one day and the heart rate was 112BPM.  I was contacted by the Dr. who said it was borderline low and that I needed a repat ultrasound in one week.    After researching the net and talking to others I found that the rate is really in normal range according to others who experienced the same thing.  I contacted my physician to ask him for his reference range and he then stated he wasnt as concerned with the heart rate since it so early in pregnancy but is concerned with my progersterone level (Which was 18).  He started me on Prometrium Suppositories 200mg twice a day.  I am taking it now but I am really worried about miscarrying.  I miscarried once before and it really took a toll onme both emotionally and physically.  How well does progesterone treatment really work in preventing miscarriage?  Are there risks to the unborn baby?  Has anyone else been in this kind of situation?  Responses are GREATLY APPRECIATED!!!

[JoyRenee]

Progesterone is NEEDED, ESSENTIAL in pregnancy. It supports the pregnancy. If your levels are low, your body will tell itself, "Not pregnant" and then you'll miscarry, even a live little baby. The progesterone is not going to harm baby whatsoever. And there are MANY women who've had to go through this and had their beautiful babies full term!!! It's more common and normal than you think!

[kazwel]

Yes, the suppositories do work in help preventing m/c.   Low Progesterone can be the cause of m/c.  
I was on 100mg 3x a day untill my 8th week  i am 12 weeks tomorrow.  The only thing i would recomend is investing in some panty liners.  they tend to leak.  but dont worry, they will do their job.
You would be surprised to hear just how many of us have been in this situation.  You are not all alone.  

kazwel