How long will it take for the embryo to implant after the transfer?

Embryo implantation is the process through which the embryo attaches to the endometrium to continue developing and initiate pregnancy. This process can only occur when the endometrium is receptive, a phase known as the implantation window, which lasts approximately 4 days.

How Long Does It Take for the Embryo to Implant?

• In a natural cycle, a woman with regular cycles will have the implantation window between days 19 and 21 of her menstrual cycle.
• In IVF treatments, the time of implantation depends on the stage of the embryo at transfer:
  • 3–Day–embryo: Implantation may take 3–5 days.
  • Blastocyst (5–Day–embryo): Implantation usually occurs 1– 2 days after transfer.

What Are the Phases of Implantation?

1. Hatching: The embryo sheds its zona pellucida, the external membrane that protects it in the early days after fertilization. In IVF, hatched blastocysts can be transferred if they have already hatched during cultivation or through assisted hatching.

1. Apposition: The embryo guides itself over the endometrial tissue so that its inner cell mass is positioned toward the endometrium.

1. Adhesion: The trophectoderm of the blastocyst attaches to the endometrial epithelium and remains adhered thanks to adhesion molecules.

1. Invasion: The embryonic trophectoderm proliferates into the endometrium, displacing epithelial cells until it comes into contact with maternal blood. During this phase, implantation bleeding may occur.

What Factors Influence the Implantation Process?

• Embryo quality: For the embryo to attach to the endometrium, it must have reached the hatched blastocyst stage, meaning it has shed its zona pellucida.

• Endometrial receptivity: The endometrium must meet specific criteria, including a thickness of 7 to 10 mm, to support implantation.