The implantation window
Embryo transfer is the final step in the IVF protocol. Next, the embryo begins the process of implantation to the inner layer of the uterus - the endometrium.
The implantation will be succesfull if the endometrium is healthy and has a normal structure.
If the thickness of the endometrium is 9-11 mm, it is considered good and contributes to successful implantation. The structure of the mucous membrane of the uterus should be three-layer.
The period of maximum receptivity of the endometrium is called the “implantation window”. The opening of the implantation window occurs in the natural menstrual cycle on the 6-10th day after ovulation, which corresponds to the 20-24th day of the menstrual cycle. It remains open for about 2 days.
In some cases, due to the physiological characteristics of the woman’s body or under the influence of hormone replacement therapy, the period may change and the timing of its onset in a smaller / larger direction.
The opening of the implantation window is accompanied by the appearance of pinopodia - these are smooth protrusions of the surface epithelial cells of the endometrium. Having reached the maximum value, they form folds, resembling flowers or mushrooms. If pinopodia is not enough, the “implantation window” will be inferior. All this can lead to a negative IVF result. The causes of such phenomena can be hormonal imbalance, the infectious process of the genital area, and surgical interventions.
Low receptivity of the endometrium is one of the reasons that reduces the effectiveness of ART programs, along with chromosomal abnormalities of embryonic cells. So in 25% of women who face problems with implantation of the embryo, a change in the period of the “implantation window” is also observed.