Threatened miscarriage and biochemical pregnancy are two important terms used to describe the state of pregnancy in early stages, but they are two completely different physiological states.

First, threatened miscarriage refers to a situation where an intrauterine pregnancy has been confirmed and the gestational sac is unstable or affected by external stimuli, showing symptoms such as lower abdominal pain and spotting. These symptoms merely indicate signs of a possible miscarriage, and with timely treatment, it is possible to revert to a normal pregnancy.

Second, a biochemical pregnancy is a type of natural miscarriage. It refers to early pregnancy where the HCG levels are relatively low, no clear gestational sac has formed, and upon re-examination, the HCG levels are found to decrease quickly, accompanied only by minimal vaginal bleeding.