Frozen Embryo Transfer: Natural Cycle versus Hormone Replacement Therapy (HRT)
The development of the vitrification (i.e. ultra‑rapid freezing) technique for embryo freezing has been the most important contributing factor in terms of improving the results and safety of in vitro fertilisation over the last decade. As a result of the development of this technique, there has been a large increase in the number of frozen embryo transfer cycles performed on a daily basis.
Advantages of frozen embryos
The main advantage we can observe with this process is that the pregnancy rates obtained are the same as in fresh embryo transfer cycles, but without the disadvantages that ovarian stimulation treatment has: financial costs, risk of ovarian hyperstimulation syndrome, psychological distress, etc.
Ovarian stimulation treatment, which is essential to the IVF technique to obtain several eggs and a good number of developing embryos in order to optimise the process, is rendered unnecessary in frozen embryo transfer cycles. For a frozen embryo transfer we only need an endometrium that has been properly prepared and synchronised with the embryo that will be transferred. A correct endometrial preparation can simply be achieved spontaneously over the course of the female’s regular ovulatory cycle (natural cycle preparation), or the endometrial preparation can be induced through the sequential administration of the hormones oestradiol and progesterone. The latter is what we refer to as Hormone Replacement Therapy (HRT).
Method for frozen embryo transfer
Both methods of endometrial preparation have proven to be equally effective when it comes to the results. For that reason, at URE Centro Gutenberg the choice between one method and another will be made exclusively based on medical criteria and the patient’s comfort and safety. This is why, as long as the patient has regular cycles and ovulates correctly, endometrial preparation in a natural cycle is the method that the majority of our patients decide to use.
Dr. Juan José Sánchez Rosas