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Embryo transfer is the most long-awaited final stage of in vitro fertilization (IVF). During embryo transfer (ET), the embryo is transferred into the uterine cavity of the expectant mother.
After the transfer of the embryo into the uterine cavity, there is a waiting period in the IVF protocol. The doctors did everything they could, and all that remains is to follow the recommendations of the reproductive specialist and wait for the results of the HCG (human chorionic gonadotropin) analysis. 14 days after ET is considered a two-week wait, we recommend that a woman shoudn’t take a pregnancy test until two full weeks have passed.
But it’s so interesting to find out what happens to our embryo there!
- First day. The blastocyst begins to undergo hatching, “hatching” outward from its shell, the cells of the embryo continue to divide.
- The second day is crucial, because it is at this time that the embryo begins to attach and prepares to penetrate the lining of the uterus. The blastocyst continues to grow.
- The third day. The embryo penetrates and burrows into the endometrium to firmly attach itself there.
- The fourth day. Germ layers are formed, and the blastocyst turns into a gastrula.
- The fifth day. The gastrula grows into the endometrium and begins to receive nutrients from it. It is during this period that discomfort in the lower abdomen may increase.
- The sixth day. The primary formation of the future placenta takes place – villi that provide nourishment to the embryo.
- The seventh day. The embryo begins to secrete hCG, which stimulates further intrauterine development and restructuring of the mother’s body to support pregnancy.
Thus, everything most important happens in 7 days. But we will start doing tests and taking analyzes in another week. At such an early stage, the sensitivity of the tests is not enough to objectively determine pregnancy.
When is it better to take a pregnancy test after embryo transfer? The timing of the pregnancy test after the embryo transfer is crucial. To avoid false negative or positive results, it is important to wait an appropriate amount of time before taking a pregnancy test. Generally, at least 10 days should pass after the transfer of fresh or thawed blastocyst stage embryos before a pregnancy test is performed. This gives enough time for human chorionic gonadotropin (hCG) to accumulate in the woman’s body.
Understanding hCG levels
HCG is a hormone produced by the villi of the chorion (future placenta) after implantation of the embryo to the endometrium of the uterus. This is a key indicator of pregnancy, and its levels can be detected with blood tests or home pregnancy tests. However, it is important to remember that hCG levels can vary significantly among women and depending on the characteristics of the course of pregnancy.
Several factors can affect hCG levels, such as:
- Type of embryo transfer: hCG levels may differ between fresh and thawed embryo transfers.
- Number and quality of trophectoderm cells (cells of the future placenta) at the time of transfer of the embryo into the uterine cavity.
- Stages of embryonic development on the day of embryo transfer (the 8th cell stage of embryo development or the blastocyst stage, when the embryo already has 156-200 cells)
- Number of embryos transferred: transferring two embryos gives a higher hCG level.
- Preparations for preparing the female body for embryo transfer and support for confirmation of pregnancy.
- Іndividual Variation: Every woman’s body is unique, and hCG levels can vary accordingly.
Immediately following the results of HCG, the reproductive doctor conducts an ultrasound of the pelvis 2 weeks after the embryo transfer in order to visualize the fetal egg in the uterine cavity and confirm pregnancy. It is possible to see a fertile egg in the uterine cavity already at a level of hCG in the blood of 750 mIU/ml. Until then, it is imperative to continue all medical support prescribed by the reproductive doctor.