Endometrial Preparation for Embryo Transfer

The transfer of frozen embryos can be done in a natural cycle or in a substituted cycle. The difference between both techniques consists in the way of preparing the endometrium so that it is receptive and the embryos can implant:

Natural cycle

takes advantage of the endogenous secretion of estrogen and progesterone by the ovaries throughout the menstrual cycle.

Replacement cycle

the secretion of endogenous hormones is inhibited and then these are administered by hormonal drugs. Specifically, estrogen patches and progesterone eggs are often used.