Glossary of Terms

December 2016

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Many technical terms are used in fertility treatment that may not be clear to couples coming to assisted reproduction centers. The aim of this glossary is to explain the terms and abbreviations so that they are clear and understandable to anybody interested in this topic.

Assisted Reproduction

Abbreviations and terms used during assisted reproduction procedures and their explanations:


  • Ovulation Induction: hormonal therapy administered to women with ovulatory disorders. This is a non-invasive technique of assisted reproduction which controls egg maturity and release for natural fertilization. The undesirable effect associated with this technique can multiple pregnancy.
  • Sperm Analysis: a quality test to evaluate male ejaculate, including sperm concentration (sperm count, number of sperm per milliliter), sperm motility (the proportion of motile and immotile sperms and character of their movement) and morphology (shape of sperm).
  • IUI, Intrauterine Insemination: a technique performed during the woman's ovulation period. In this technique, sperm of the partner is introduced into the uterine cavity through a thin catheter. It is a minimally invasive method, usually completely painless, with minimal risks. It is used if the sperm has low sperm count or poor motility. It is also used after detecting a higher impermeability of the cervical mucus.
  • AID, Artificial Insemination by Donor: if the partner's sperm cannot be used, a sperm from an anonymous donor stored in a sperm bank can be used with the consent of the couple.
  • Hormonal Stimulation: an individual therapy, which aims to obtain the optimal number of mature eggs for assisted reproduction cycle (e.g. IUI, IVF or ICSI). It is performed by stimulating the woman's ovaries using hormonal drugs, usually in the form of injections.
  • Embryo Transfer: transfer of embryo cultured in an incubator back into the woman's uterus.
  • IVF, In vitro Fertilization: a method of infertility treatment, where the sperm is added to the female eggs to allow fertilization. Fertilization takes place in a culture solution in the clinic’s laboratory under strictly defined and controlled conditions. Fertilization takes place spontaneously, i.e. the sperm moves actively towards the egg and penetrates its shell. The co-culture lasts 16 to 20 hours, and after this time, the success of fertilization is determined and embryo may be transferred back into the uterus.
  • ICSI, Intracytoplasmic Sperm Injection: a micromanipulation technique used to incorporate a single sperm directly into the egg. The technique is carried out under a specially adapted microscope at high magnification using a microneedle. It is used in case of low sperm count or low sperm mobility.
  • IMSI, Intracytoplasmic Morphologically Selected Sperm Injection: the sperm is selected based on morphological assessment of individual sperm cells. Selection is carried out using a special microscope at high magnification. Spermatozoa with the best morphology are used for micromanipulation-assisted fertilization.
  • PICSI, Preselective Intracytoplasmic Sperm Injection: a technique that mimics the natural selection of mature sperm. During the natural fertilization process, the human oocyte is successfully fertilized by the sperm, which is capable of binding to a chemical substance (hyaluronan) present on its surface. The principle of this method is therefore binding mature sperm to a special gel containing hyaluronan. The selected spermatozoa are then used for micromanipulation-assisted fertilization.
  • OHSS, Ovarian Hyperstimulation Syndrome: an excessive reaction to hormonal stimulation of the ovaries, which is manifested by pain, considerable enlargement of the ovaries and formation of free fluid in the abdominal cavity. Women younger than 30 years are particularly vulnerable to this syndrome.
  • PGD, Preimplantation Genetic Diagnosis: a technique for identifying chromosomal aberrations, changes or hereditary diseases of the embryo before transferring to the uterus.
  • PGS, Preimplantation Genetic Screening: searching for any change in the genetics of the embryo.
  • Extended Culture: the extended culture of fertilized oocytes allows to transfer the best embryo into the uterus.
  • HB, Hatching Blastocyst: on day 4 after fertilization, the embryo develops to the blastocyst stage, which is followed by rupture of zona pellucida. The embryo leaves its protective shell (hatching) and is ready to implant itself in the uterine lining.
  • AH, Assisted Hatching: a micromanipulation technique, during which the glycoprotein envelope of the oocyte is artificially disrupted just before introduction into the uterus. It is performed in all embryos that are available for the client on the fourth day of culture, when the embryos reach the compact stage. This technique increases the chance of implantation of the embryo in the endometrium.
  • Embryo Monitoring: a real-time monitoring of embryo development. The camera scans the embryo development in short timeframes continuously throughout their development in the incubator and allows to choose the best developed embryos for the transfer. This method is often offered to patients suffering from miscarriages.
  • Cryopreservation of eggs / sperm / embryo: a gentle method of preservation in special containers in liquid nitrogen at –196°C. Currently the most commonly used method of cryopreservation is vitrification.
  • Vitrification: a cryopreservation technique that uses very rapid freezing and thawing at relatively high concentrations of cryoprotectants. Cryoprotectants are substances that protect cells and tissues from cold damage caused by ice crystal formation.
  • FET, Frozen Embryo Transfer: if a woman has had her embryo frozen, they can be transferred in the optimal phase of the natural cycle without prior stimulation. If properly vitrified (frozen), almost 100% of embryos survive the thawing process. It is advisable to transfer embryos individually, so it is common to freeze each embryo separately.
  • PESA, Percutaneous Epididymal Sperm Aspiration: a method used to retrieve sperm from the epididymis, which is used when it is not possible to obtain sperm naturally by ejaculation. Under general anaesthesia, a needle is used to penetrate through the skin into the epididymis and aspirate liquid from it. The liquid obtained is then used to seek sperm suitable for egg fertilization.
  • MESA, Microsurgical Epididymal Sperm Aspiration: a microsurgical sperm aspiration from epididymal tubules where the sperm mature. This technique is used if the connection between the epididymis and the urethra is absent or damaged. The fluid obtained by aspiration is processed in the laboratory and the spermatozoa retrieved are then used for the ICSI technique. MESA is carried out under general anaesthesia.
  • TESE, Testicular Sperm Extraction: is used to collect 6 to 10 small samples of germinal tissue through small incisions in the sperm-producing testicular tubules. It is performed when the MESA technique was not successful. The sperm obtained from the collected tissue is used for the ICSI technique. TESE is carried out under general anaesthesia.

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