Why do doctors check hcg doubling times?

Health of Preg: A healthy preg, esp. 1st trimester, will approximately double HCG values every 48 hrs. Anything less makes your doctor concerned for.Poss miscarriage or ectopic pregnancy.

To see if teh preg: Is progressing normally when you are early to make sure it will be a normal iup and not a miscarr or an ectopic and also Progesterone levels should be checked along with the bhcgs.