Serial HCG calculator
For management of pregnancy of unknown location
Ectopic pregnancy and miscarriage: diagnosis and management NICE guideline, 2012
In cases of pregnancy of unknown location, NICE recommends measurement of serum HCG on two occasions 48 hours apart. A rise in HCG of 63% or greater is likely to be associated with a developing intrauterine pregnancy (although this does not exclude ectopic pregnancy), and a fall of at least 50% is likely to be associated with a failing pregnancy.