Pregnancy is usually not detectable on day 4 of embryo transfer.
After the embryo has been laid, the ectoderm will gradually produce HCG, which will then be secreted into the bloodstream, and then from the kidneys into the urine as time increases. You can determine if you are pregnant by testing for HCG in the blood or urine.
It takes some time for the HCG concentration in urine to gather. Generally speaking, pregnancy cannot be detected on the 4th day of embryo transfer for the time being, because the time is short and the HCG concentration in blood is still low, and the HCG concentration in urine is even lower, so the test may be inaccurate.
It will take some time for the embryo to settle and then for HCG to be detected after the transfer. Generally, blood or urine hCG levels are measured 2 weeks after embryo transfer to determine pregnancy, and ultrasound is performed 4 to 5 weeks after transfer to determine if there is an intrauterine clinical pregnancy.
It should be noted that sometimes pregnancy test strips can be inaccurate, it is recommended to go directly to the hospital to draw blood to check blood HCG, and also check the serum level of progesterone. If there is any abnormality after the embryo transfer, it is recommended to consult a doctor promptly.