Low progesterone?

Kehly
I went in last Thursday because I had some spotting (since resolved). They tested HCG levels and progesterone. HCG  levels were 87,000 on 9/24 and 98,000 on 9/26, so we are good there. However my progesterone levels were low, so they want me to take a progesterone supplement twice a day through week 12. Anyone heard of this? I hate taking hormones if I don't have to. They said it's not abnormal to have this, but I've never heard of this. Anyone else have this issue and have everything be fine? First pregnancy.. 9 weeks 3 days. Thanks!