Frozen embryo transfers can be performed in either a natural or a substituted cycle. In the case of the natural cycle, the natural hormones of the patient's menstrual cycle are used and the evolution of the follicle and endometrium is monitored by ultrasound, without administering any medication. Once ovulation has occurred (release of the mature egg), treatment with progesterone is initiated.
In substituted cycles, estrogens are administered to prepare the endometrium, either in the form of patches or pills. When the endometrium is observed by ultrasound to be prepared, progesterone is administered.
It will be done in one way or another depending on the characteristics of each patient: if she has a menstrual cycle, results of previous cycles.... In addition, there may also be variations in these treatment guidelines that we have mentioned, such as administering GnRH analogs, for example.
