Don’t glance over the glossary - you might miss a new acronym

When working with assisted reproduction we use a lot of different terms and definitions. This blog post will give you an update on the rather new acronym PGT (preimplantation genetic testing) as well as a glossary of common and useful terms.

Harmonisation of terms completed by experts

In an attempt to harmonise terms and definitions the International Committee for Monitoring Assisted Reproductive Technologies (ICMART) first published a glossary of 53 terms and definitions in 2006. This list has been expanded over the years and in 2017 the result of 25 global professionals, representing different specialties, was published in Fertility and Sterility. Before publication, the terms and definitions were discussed and further refined by a larger group of experts.

We are working in a changing field

The list is now composed of 283 terminologies that are utilised within infertility and fertility care. Many terms have been acronynomised. One has to admit we work in an acronym rich field and just when you think you might have memorised them all, they start changing!

PGS and PGD are now PGT

One acronym that you might not recognise in the glossary is PGT. It stands for preimplantation genetic testing and now replaces PGS (preimplantation genetic screening) and PGD (preimplantation genetic diagnosis).

The consensus definition for PGT is - a test performed to analyse the DNA from oocytes (polar bodies) or embryos (cleavage stage or blastocyst) for HLA-typing or for determining genetic abnormalities. PGT is then further sub-categorized by a suffix:

• PGT-A for aneuploidies (previously PGS)
• PGT-M for monogenic/single gene defects (previously PGD)
• PGT-SR for chromosomal structural rearrangements (previously PGS translocation)

A selection of terms and definitions at your service

We have listed a selection of the most commonly used terms and definition from "The international Glossary on Infertility and Fertility Care 2017", in case you do not have time to dwell on all 283 definitions. 

• Age specific fertility rate (ASFR) The number of live births per woman in a particular age group in a specific calendar year expressed per 1000 women in that age group.

• Assisted reproductive technology (ART) All interventions that include the in vitro handling of both human oocytes and sperm or of embryos for the purpose of reproduction. This includes, but is not limited to, IVF and embryo transfer ET, intracytoplasmic sperm injection ICSI, embryo biopsy, preimplantation genetic testing PGT, assisted hatching, gamete intrafallopian transfer GIFT, zygote intrafallopian transfer, gamete and embryo cryopreservation, semen, oocyte and embryo donation, and gestational carrier cycles. Thus, ART does not, and ART-only registries do not, include assisted insemination using sperm from either a woman's partner or a sperm donor. (See broader term, medically assisted reproduction, MAR.)

• Cohort total fertility rate (CTFR) The observed average number of live born children per woman applied to a birth cohort of women as they age through time. This is obtained from data on women after completing their reproductive years.

• Congenital bilateral absence of the vasa deferentia (CBAVD) The absence, at birth, of both duct systems (vas deferentia) that connect the testes to the urethra and may be associated with cystic fibrosis transmembrane conductance regulator (CTFR) gene mutation. Although the testes usually develop and function normally, men present with azoospermia.

• Double embryo transfer (DET) The transfer of two embryos in an ART procedure. This may be elective (eDET) when more than two embryos of sufficient quality for transfer are available.

• Elective single embryo transfer (eSET) The transfer of one (a single) embryo selected from a larger cohort of available embryos.

• Embryo transfer (ET) Placement into the uterus of an embryo at any embryonic stage from day 1 to day 7 after IVF or ICSI. Embryos from day 1 to day three can also be transferred into the Fallopian tube.

• Frozen-thawed embryo transfer (FET) cycle An ART procedure in which cycle monitoring is carried out with the intention of transferring to a woman, frozen/thawed or vitrified/warmed embryo(s)/blastocyst(s). Note: A FET cycle is initiated when specific medication is provided or cycle monitoring is started in the female recipient with the intention to transfer an embryo.

• Gamete intrafallopian transfer (GIFT) An ART procedure in which both gametes (oocytes and spermatozoa) are transferred into a Fallopian tube(s).

• In vitro fertilisation (IVF) A sequence of procedures that involves extracorporeal fertilisation of gametes. It includes conventional in vitro insemination and ICSI.

• In vitro maturation (IVM) A sequence of laboratory procedures that enable extracorporeal maturation of immature oocytes into fully mature oocytes that are capable of being fertilized with potential to develop into embryos.

• Initiated medically assisted reproduction cycle (iMAR) A cycle in which the woman receives specific medication for ovarian stimulation or in which cycle monitoring is carried out with the intention to treat, irrespective of whether or not insemination is performed, follicular aspiration is attempted in an ovarian stimulation cycle or whether egg(s) or embryo(s) are thawed or transferred in a frozen embryo transfer (FET) cycle.

• Intracytoplasmic sperm injection (ICSI) A procedure in which a single spermatozoon is injected into the oocyte cytoplasm.

• Medically assisted reproduction (MAR) Reproduction brought about through various interventions, procedures, surgeries and technologies to treat different forms of fertility impairment and infertility. These include ovulation induction, ovarian stimulation, ovulation triggering, all ART procedures, uterine transplantation and intrauterine, intracervical and intravaginal insemination with semen of husband/partner or donor.

• Microdissection testicular sperm extraction (MicroTESE) A surgical procedure using an operating microscope to identify seminiferous tubules that may contain sperm to be extracted for IVF and/or ICSI.

• Microsurgical epididymal sperm aspiration/extraction (MESA/MESE) A surgical procedure performed with the assistance of an operating microscope to retrieve sperm from the epididymis of men with obstructive azoospermia. In the absence of optical magnification, any surgical procedure to retrieve sperm from the epididymis should also be registered as MESE.

• Ovarian hyperstimulation syndrome (OHSS) An exaggerated systemic response to ovarian stimulation characterised by a wide spectrum of clinical and laboratory manifestations. It may be classified as mild, moderate or severe according to the degree of abdominal distention, ovarian enlargement and respiratory, hemodynamic and metabolic complications.

• Ovarian stimulation (OS) Pharmacological treatment with the intention of inducing the development of ovarian follicles. It can be used for two purposes: 1) for timed intercourse or insemination; 2) in ART, to obtain multiple oocytes at follicular aspiration.

• Ovulation induction (OI) Pharmacological treatment of women with anovulation or oligo-ovulation with the intention of inducing normal ovulatory cycles.

• Percutaneous epididymal sperm aspiration (PESA) A surgical procedure in which a needle is introduced percutaneously into the epididymis with the intention of obtaining sperm.

• Polycystic ovary syndrome (PCOS) A heterogeneous condition, which requires the presence of two of the following three criteria: (1) Oligo-ovulation or anovulation; (2) Hyperandrogenism (clinical evidence of hirsutism, acne, alopecia and/or biochemical hyperandrogenemia); (3) Polycystic ovaries, as assessed by ultrasound scan with more than 24 total antral follicles (2–9 mm in size) in both ovaries.

• Poor ovarian responder (POR) in assisted reproductive technology A woman treated with ovarian stimulation for ART, in which at least two of the following features are present: (1) Advanced maternal age (R40 years); (2) A previous poor ovarian response (%3 oocytes with a conventional stimulation protocol aimed at obtaining more than three oocytes); and, (3) An abnormal ovarian reserve test (i.e. antral follicle count 5–7 follicles or anti-Mullerian hormone 0.5–1.1 ng/ml (Bologna criteria); or other reference values obtained from a standardized reference population.)

• Preimplantation genetic testing (PGT) A test performed to analyze the DNA from oocytes (polar bodies) or embryos (cleavage stage or blastocyst) for HLA-typing or for determining genetic abnormalities. These include: PGT for aneuploidies (PGT-A); PGT for monogenic/single gene defects (PGT-M); and PGT for chromosomal structural rearrangements (PGT-SR).

• Preimplantation genetic diagnosis (PGD) and screening (PGS) These terms have now been replaced by preimplantation genetic testing PGT. (See term PGT and its definitions.)

• Single embryo transfer (SET) The transfer of one embryo in an ART procedure. Defined as elective (eSET) when more than one embryo of sufficient quality for transfer is available.

• Testicular sperm aspiration/extraction (TESA/TESE) A surgical procedure involving one or more testicular biopsies or needle aspirations to obtain sperm for use in IVF and/or ICSI.

• Time to pregnancy (TTP) The time taken to establish a pregnancy, measured in months or in numbers of menstrual cycles.

• Total fertility rate (TFR) The average number of live births per woman. It may be determined in retrospect, observed data (Cohort Total Fertility Rate, CTFR) or as an estimated average number (Period Total Fertility Rate, PTFR).

• Zygote intrafallopian transfer (ZIFT) An ART procedure in which one or more zygotes is transferred into the Fallopian tube.