Generally speaking, blastocysts can be detected about 12 days after the transfer. After the blastocyst is transplanted, it usually starts to implant in about one week, and the implantation is completed in about 12 days. During the process of implantation, the hormone secretion in the body starts to increase, and the implantation of blastocyst can be judged by taking blood test for HCG. If the blastocyst is well implanted, the HCG value will double every other day. If the blastocyst is not well established or not well developed, then the HCG will not usually double. If you check with a pregnancy test, it should be done 15 days after the transfer of the blastocyst, using the morning urine to check the concentration of urine HCG, which is higher and more accurate.