The transfer of frozen thawed embryos may be scheduled in a pharmaceutically controlled cycle or in a natural cycle by monitoring ovulation.

Pharmaceutically controlled cycle

In this protocol, only the endometrium is prepared with drugs for the embryo transfer. Initially, the pituitary function is suppressed in order to prevent a premature LH surge and therefore ovulation, which would result in the release of progesterone and its effect on the endometrium at the wrong time. A cycle with hormonal replacement therapy would be the best solution.

Suppression starts on the 21st or the 2nd day of the cycle, as with the long protocol, the same steps of controlling the suppression are followed. Stimulation of ovarian function is not necessary. During the 2nd phase of the treatment, the endometrium is prepared with pills or patches of 17-β oestradiol (white pills of Estopause or Cyclacur and Dermestril Estraderm patches. Monitoring is performed by vaginal ultrasound, during which the thickness and the structure of the endometrium are checked. At the end, progesterone pills are also administered and the day of embryo transfer is scheduled.

Natural cycle

The transfer of frozen thawed embryos can be performed in a natural cycle. In this case, the development of the follicle is monitored along with the endometrium with a series of transvaginal ultrasounds and hormone measurements. Ovulation is predicted or induced and the day of embryo transfer is scheduled.