hi what does hcg mean? is it like how big the baby is ?

You may click on this link to read and understand https://www.ncbi.nlm.nih.gov/books/NBK532950/#:~:text=Human%20chorionic%20gonadotropin%20(hCG)%20is,useful%20following%20an%20aborted%20pregnancy. Also at every week your hCG level will change and gradually will decrease towards third trimester.