Embryo transfer (ET)
Embryo transfer is a gentle introduction of the embryo (embryos) into the uterus cavity by a thin catheter under ultrasound control. The embryos are introduced with a small amount of fluid – the medium. The performance is fast, painless, and does not require anaesthesia. The number of embryos introduced depends mainly on the age of the patient, the number of the previous IVF cycles, and the female patient’s wish. Mostly 1 – 2 embryos are transferred. The patient may go home in about one hour after the ET, the first pregnancy test is made 2 weeks after the ET.
The technique, in which an orifice is made by a laser or micro manipulative needle into the glycoprotein coat (zona pellucida) of the embryo, through which the embryo later leaves the coat (a process called hatching). This technique is recommended to be performed in embryos with a thick zona pellucida or in cryopreserved embryos where the cryopreservation process may induce changes in the hardness of the ovum shell.
The embryo is surrounded by a 13-15 μm thick acellular matrix, a pellucid zone. It is composed of glycoproteins, carbohydrates, and the proteins specific for the zona pellucida. The process of artificial disturbance of the zona pellucida helps the developing embryo to get rid of the zona pellucida and to attach to the uterine wall, which increases the likelihood of achieving vital pregnancy.
Indications for assisted hatching: higher age – the patients over 38 years of age, female patients with FSH elevations on day 3 (>10.0), female patients with previous failed pregnancy cycles, thick or abnormal zona pellucida, with cryopreserved embryos.