This is one of the key moments of any reproduction treatment that requires fertilization in the laboratory.

When the eggs have fertilized, embryonic development begins. Once the embryos reach blastocyst stage (day 5 or 6 of embryo life), these are ready to be transferred to the uterus. Specialists assess their quality and morphology to select the one that will be transferred; any surplus embryos will be vitrified to be used later if necessary.

Prior to the embryo transfer, the gynecologist will check that the patient's endometrium is ready (sometimes it is best not to waste any embryos and cancel the transfer if the endometrium is not thick enough). Endometrial preparation can be done in a natural cycle (taking advantage of the patient's cycle and with minimal medication) or a medicated cycle (to ensure the endometrium has the desired thickness and hormone levels are correct). The choice will depend on the woman's diagnosis and history.

When all parameters are correct, the transfer is performed in the operating room. It is a simple procedure during which the embryo is placed inside the uterus through the vagina using a fine catheter. The specialist will be guided by an ultrasound scan to locate the best place for implantation.

The procedure lasts just a few minutes and does not require anesthesia or sedation. Patients may experience some slight discomfort, but rarely pain. The patient will rest at the clinic for half an hour, being able to resume her regular activities afterwards, but avoiding intense efforts.


After the transfer, the “beta wait” begins: a period during which some patients experience symptoms such as nausea, abdominal distension or drowsiness. These symptoms are closely associated with pregnancy and often lead to confusion, but are triggered by medication.

Sometimes, slight spotting may also occur. This is not the period and it does not imply that the transfer has gone wrong. It is usually the so-called implantation bleeding, which occurs as a result of the implantation of the embryo in the uterus.

Finally, the only way to confirm the pregnancy has been achieved is by detecting BHCG in the blood; a blood analysis that is performed twelve days after the transfer.