, as a general rule, hCG beta numbers should double every 36 to 48 hours. A dramatic decrease in the levels may indicate a miscarriage has occurred or is possible, whereas a level that stays the same or falls well below the normal range may indicate an ectopic pregnancy. Beta hCG levels can also be used to identify a multiple pregnancy like twins, triplets, or multiples. In such cases the hCG levels will peak out by the end of the first trimester. Reference: Babyhopes.com