Is Progesterone Suppositories Necessary To Avoid Miscarriage?

Hello,

I have a history of miscarriages (2 documented, possibly 3) and have done several blood panels and and an HSG to rule out existing problems, and they have all come back fine. I just found out that I am pregnant, with hcg levels at 51.3, and progesterone levels at 36.11, for being 4 weeks along. Although my OB says my hcg are somewhat low, and progesterone levels look great, he wants to put me on progesterone suppositories because of my history. Do you think this is necessary?