People who opt for IVF treatment face a phase where they feel the needles of a clock to be stuck at a point and sand of an hour glass to have stopped pouring down, their heart sinks a million times in that 2 week periods after the embryo transplant after which they are finally allowed to check where the transplantation has successfully took place or not and the woman is pregnant or not. This time is indeed the most dreadful time of the entire cycle and nerve-wrecking.
It's certainly realised that it's every difficult for the couple to be feeling suspended between uncertainity and hope but it is very important to understand the reason Doctors ask the couple to wait for this period before taking up the test.
HCG (Human Chorionnic Gonadotropin) is an hormone which is produced by the trophectoderm cells of the embryo, it is produced in detectable quantities only after the embryo implants properly. A pregnancy test measures the amount of beta HCG in the body. Because it takes 3-8 days for the implantation to take place after the embryo transfer, HCG produced by the embryo will be detectable in the bloodstream only after this period of time.
As the pregnancy will progress, the hCG amount increases in the system. After 10 days past ovulation ( DPO), the average woman is found to have hCG measurement of around 25 mIU, it to 50 mIU at 12 days past ovulation, and then doubles again to 100 mIU at around two weeks past ovulation.Though the amount of hCG is seen to be varying differently as per different body type.
Pregnancy tests taken at home measure the level of HCG in urine. There are various options available in the market for pregnancy testing kits, every kit has different level of sensitivity. In case, a pregnancy test is sensitive to 100 mIU, will not indicate of pregnancy if hCG level only 75 mIU. Also, these pregnancy tests can't detect a level lower than 25, so can't be trusted to be accurate until a few days after embryo implantation. To avoid any kind of unnecessary disheartenment that can be caused to the patient, the patients are told to wait for 2 weeks time. In case a test is taken before time, there wouldn't be a high enough level of HCG to detect pregnancy.
This is also a reason why patients are advised to take blood tests for HCG instead of urine tests. They're not just more reliable and accurate but they also give the doctor a number that can be measured and monitored.
Unfortunately, blood tests also don't show accurate results very soon after the embryo transfer. This is because there could be traces of HCG in the body due to HCG trigger shot (Choragon or Ovidrel) given by the doctor to trigger off ovulation 36 hours prior to egg collection. Hence, blood test taken too early will always be positive, as this HCG will show up. It can certainly give you a blast of happiness for a moment, but it would be nothing but a false hope, it's better to wait for the time suggested and then take test to figure out the actual result. Patients taking IVF treatment are advised one thing the most, and that is to “Keep patience”.