After fertilisation, early human embryos initially divide roughly once per day, giving a four-cell embryo on the second day, an eight-cell embryo on the third day, etc. On the third day, the embryonal genome - the embryo’s own genetic information - is activated and the culture medium requirements change. It is therefore necessary to switch to a different medium at this point at the latest. From the fourth day of culture, development occurs more quickly, and can differ greatly between embryos. Typically, on the fourth day, the morula stage has been reached, and blastocysts can be observed on the fifth or sixth day. Prolonged culture until the blastocyst stage is recommended in particular for patients who only want to transfer one selected embryo in order to avoid multiple pregnancy. However, this approach is primarily useful if there are sufficient fertilised egg cells with good potential for development. Observing their development behaviour in culture can also provide insights into potential issues. In some cases, development is so disrupted that ultimately no transfer will be carried out. Despite all technical adjustments, development in culture is not directly comparable to development in the human body.
If the fertilized egg cells continue to divide as desired, we insert the embryos into the uterine cavity around two to five days after the follicular puncture. This so-called embryo transfer takes place using a thin tube and is completely painless. If desired, the partner can be present in the operating room during the procedure.
After artificial fertilisation, the possibility of multiple pregnancy is increased in all age groups, especially if more than one embryo is transferred. Multiple pregnancies pose increased risks for both mother and children. The proportion of these high-risk pregnancies could be reduced from approx. 18% to 9% by increasing the number of single embryo transfers (Single Embryo Transfer; SET). We are therefore striving to further increase the proportion of SETs and, as a rule, insert only a single embryo into the uterus.
In the subsequent phase, the embryo should implant into the endometrium. In order to support the corpus luteum, you will be given further hormonal treatment with oestrogen and progesterone (administered orally or vaginally). During this time, you should avoid all significant physical effort, vibrations and shocks, for example as a result of exercise, dancing, horseback riding, intercourse and similar activities.
A simple blood test is used for confirmation of pregnancy 14 days after follicular puncture.
If the blood sample 14 days after embryo transfer is positive, in other words, you are pregnant, the hormones must still be taken - even if bleeding occurs, as this can also happen during a normally progressing pregnancy.
In the regrettable case of a negative test, hormonal treatment is stopped. We will then inform you of the further course of action. If cryopreserved fertilised eggs or embryos are available, these can be used to continue the treatment.
If no frozen eggs or embryos are available, the stimulation therapy for follicular puncture can only be restarted during the second following period, as the ovaries require a short break before undergoing another stimulation cycle.