Assisted Reproductive Technology - Glossary
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The following glossary of medically assisted reproduction (MAR) terms is based upon a WHO meeting in 2008 and has additional terms that have been added. The purpose is to establish a consensus to allow better analysis of statistical and health data. The full paper is available from the WHO website and was published in both Fertility and Sterility and Human Reproduction.
- "Seventy-two clinicians, basic scientists, epidemiologists and social scientists gathered together at the World Health Organization headquarters in Geneva, Switzerland, in December 2008. Several months before, three working groups were established as responsible for terminology in three specific areas: clinical conditions and procedures, laboratory procedures, and outcome measures. Each group reviewed the existing International Committee for Monitoring Assisted Reproductive Technology glossary, made recommendations for revisions and introduced new terms to be considered for glossary expansion."
The International Committee Monitoring Assisted Reproductive Technologies' (ICMART) mission is:
- "to collect, analyze and disseminate comprehensive international data on assisted reproductive technologies that are useful to all stakeholders in ART, to publish results of research on these data; and to promote the international development of standardized definitions and assisted reproductive technology registries."
Note that glossary has been edited from the original publication, including some additional terms, listed acronyms and links that did not form part of the original glossary. For a complete list of embryological terms see Glossary.
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An in vitro procedure in which the zona pellucida of an embryo is either thinned or perforated by chemical, mechanical, or laser methods to assist separation of the blastocyst.
Assisted reproductive technology
(ART) All treatments or procedures that include the in vitro handling of both human oocytes and sperm or of embryos for the purpose of establishing a pregnancy. This includes, but is not limited to, in vitro fertilization and embryo transfer, gamete intrafallopian transfer, zygote intrafallopian transfer, tubal embryo transfer, gamete and embryo cryopreservation, oocyte and embryo donation, and gestational surrogacy. ART does not include assisted insemination (artificial insemination) using sperm from either a woman’s partner or a sperm donor. (More? Assisted Reproductive Technology)
Treatment cycles that use the women.s own oocytes or embryos.
(preclinical spontaneous abortion/ miscarriage) A pregnancy diagnosed only by the detection of hCG in serum or urine and that does not develop into a clinical pregnancy.
An embryo, 5 or 6 days after fertilization, with an inner cell mass, outer layer of trophectoderm, and a fluid-filled blastocele cavity.
An ART cycle in which ovarian stimulation or monitoring has been carried out with the intention to treat, but which did not proceed to follicular aspiration or, in the case of a thawed embryo, to embryo transfer.
A pregnancy diagnosed by ultrasonographic visualization of one or more gestational sacs or definitive clinical signs of pregnancy. It includes ectopic pregnancy. Note: Multiple gestational sacs are counted as one clinical pregnancy.
Clinical pregnancy rate
The number of clinical pregnancies expressed per 100 initiated cycles, aspiration cycles, or embryo transfer cycles. Note: When clinical pregnancy rates are given, the denominator (initiated, aspirated, or embryo transfer cycles) must be specified.
Clinical pregnancy with fetal heart beat
Pregnancy diagnosed by ultrasonographic or clinical documentation of at least one fetus with heart beat. It includes ectopic pregnancy.
All structural, functional, and genetic anomalies diagnosed in aborted fetuses, at birth, or in the neonatal period.
Controlled ovarian stimulation (COS) for ART
Pharmacologic treatment in which women are stimulated to induce the development of multiple ovarian follicles to obtain multiple oocytes at follicular aspiration.
Controlled ovarian stimulation (COS) for non-ART cycles
Pharmacologic treatment for women in which the ovaries are stimulated to ovulate more than one oocyte.
Acronym for Controlled Ovarian Stimulation. (More? Controlled Ovarian Stimulation)
The freezing or vitrification and storage of gametes, zygote, embryos, or gonadal tissue.
Cumulative delivery rate with at least one live born baby
The estimated number of deliveries with at least one live born baby resulting from one initiated or aspirated ART cycle including the cycle when fresh embryos are transferred and subsequent frozen/ thawed ART cycles. This rate is used when less than the total number of embryos fresh and/or frozen/thawed have been used from one ART cycle. Note: The delivery of a singleton, twin, or other multiple pregnancy is registered as one delivery.
The expulsion or extraction of one or more fetuses from the mother after 20 completed weeks of gestational age.
Delivery rate after ART treatment per patient
The number of deliveries with at least one live born baby per patient after a specified number of ART treatments.
The number of deliveries expressed per 100 initiated cycles, aspiration cycles, or embryo transfer cycles. When delivery rates are given, the denominator (initiated, aspirated, or embryo transfer cycles) must be specified. It includes deliveries that resulted in the birth of one or more live babies and/or stillborn babies. Note: The delivery of a singleton, twin, or other multiple pregnancy is registered as one delivery.
Early neonatal death
Death of a live born baby within 7 days of birth.
A pregnancy in which implantation takes place outside the uterine cavity. (More? Ectopic Implantation)
Elective embryo transfer
The transfer of one or more embryos, selected from a larger cohort of available embryos.
The product of the division of the zygote to the end of the embryonic stage, 8 weeks after fertilization. (This definition does not include either parthenotes—generated through parthenogenesis—nor products of somatic cell nuclear transfer.)
The transfer of an embryo resulting from gametes (spermatozoa and oocytes) that did not originate from the recipient and her partner.
Embryo recipient cycle
An ART cycle in which a woman receives zygote(s) or embryo(s) from donor(s).
A procedure to reduce the number of viable embryos or fetuses in a multiple pregnancy.
(ET) The procedure in which one or more embryos are placed in the uterus or fallopian tube.
Embryo transfer cycle
An ART cycle in which one or more embryos are transferred into the uterus or fallopian tube.
Empty follicle syndrome
(EFS) Clinically defined as the failure to aspirate oocytes from mature ovarian follicles during in vitro fertilization. At least one genetic cause has been identified, a missense mutation in zona pellucida protein 3 (ZP3).
Extremely low birth weight
Birth weight less than 1,000 g. (More? Birth-Weight)
Extremely preterm birth
A live birth or stillbirth that takes place after 20 but before 28 completed weeks of gestational age.
Fetal death (stillbirth)
Death before the complete expulsion or extraction from its mother of a product of fertilization, at or after 20 completed weeks of gestational age. The death is indicated by the fact that, after such separation, the fetus does not breathe or show any other evidence of life, such as heart beat, umbilical cord pulsation, or definite movement of voluntary muscles.
Frozen-thawed embryo transfer cycle
(FET) an ART procedure in which cycle monitoring is carried out with the intention of transfering frozen-thawed embryo(s). Note: An FET cycle is initiated when specific medication is provided or cycle monitoring is started with the intention to treat.
Frozen-thawed oocyte cycle
An ART procedure in which cycle monitoring is carried out with the intention of fertilizing thawed oocytes and performing embryo transfer.
A live birth or stillbirth that takes place between 37 and 42 completed weeks of gestational age.
Gamete intrafallopian transfer
(GIFT) An ART procedure in which both gametes (oocytes and spermatozoa) are transferred to the fallopian tube.
Age of an embryo or fetus calculated by adding 2 weeks (14 days) to the number of completed weeks since fertilization. Note: For frozen-thawed embryo transfers, an estimated date of fertilization is computed by subtracting the embryo age at freezing from the transfer date of the FET cycle.
(surrogate) A woman who carries a pregnancy with an agreement that she will give the offspring to the intended parent(s). Gametes can originate from the intended parent(s) and/or a third party (or parties).
A fluid-filled structure associated with early pregnancy, which may be located inside or outside the uterus (in case of an ectopic pregnancy).
The process by which an embryo at the blastocyst stage separates from the zona pellucida. (More? Blastocyst Development(
A pregnancy or delivery with three or more fetuses or neonates.
The attachment and subsequent penetration by the zona-free blastocyst (usually in the endometrium) that starts 5 to 7 days after fertilization.
The number of gestational sacs observed divided by the number of embryos transferred.
In vitro fertilization
The termination of a clinical pregnancy by deliberate interference that takes place before 20 completed weeks of gestational age (18 weeks after fertilization) or, if gestational age is unknown, of an embryo/fetus of less than 400 g.
(clinical definition) Disease of the reproductive system defined by the failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse.
An ART cycle in which the woman receives specific medication for ovarian stimulation, or monitoring in the case of natural cycles, with the intention to treat, irrespective of whether or not follicular aspiration is attempted.
Intracytoplasmic sperm injection
(ICSI) A procedure in which a single spermatozoon is injected into the oocyte cytoplasm.
The complete expulsion or extraction from its mother of a product of fertilization, irrespective of the duration of the pregnancy, which, after such separation, breathes or shows any other evidence of life, such as heart beat, umbilical cord pulsation, or definite movement of voluntary muscles, irrespective of whether the umbilical cord has been cut or the placenta is attached.
Live birth delivery rate
The number of deliveries that resulted in at least one live born baby, expressed per 100 initiated cycles, aspiration cycles, or embryo transfer cycles. When delivery rates are given, the denominator (initiated, aspirated, or embryo transfer cycles) must be specified.
Low birth weight
Birth weight less than 2,500 g. (More? Birth-Weight)
Maternal spindle transfer
(MST) The “maternal spindle” is the group of maternal chromosomes within the egg, which are shaped in a spindle. MST involves removing the spindle from the mother’s egg before it is fertilised by the father’s sperm. The spindle is then placed into a donor egg with healthy mitochondria (from which the donor’s spindle, and therefore her nuclear material, has been removed).
Medically assisted reproduction
(MAR) Reproduction brought about through ovulation induction, controlled ovarian stimulation, ovulation triggering, ART procedures, and intrauterine, intracervical, and intravaginal insemination with semen of husband/partner or donor.
Acronym for microsurgical epididymal sperm aspiration.
Acronym for microsurgical epididymal sperm extraction.
Acronym for Microsurgical testicular sperm extraction.
Mild ovarian stimulation for IVF
A procedure in which the ovaries are stimulated with gonadotropins and/or other compounds, with the intent to limit the number of oocytes obtained for IVF to fewer than seven.
A clinical abortion where the embryo(s) or fetus(es) is/are nonviable and is/are not expelled spontaneously from the uterus.
Modified natural cycle
An IVF procedure in which one or more oocytes are collected from the ovaries during a spontaneous menstrual cycle. Drugs are administered with the sole purpose of blocking the spontaneous LH surge and/or inducing final oocyte maturation.
A pregnancy/delivery with more than one fetus/neonate.
Natural cycle IVF
An IVF procedure in which one or more oocytes are collected from the ovaries during a spontaneous menstrual cycle without any drug use.
Death of a live born baby within 28 days of birth. Neonatal period: the time interval that commences at birth and ends 28 completed days after birth.
Oocyte donation cycle
A cycle in which oocytes are collected from a donor for clinical application or research.
Oocyte recipient cycle
An ART cycle in which a woman receives oocytes from a donor.
Ovarian hyperstimulation syndrome
(OHSS) An exaggerated systemic response to ovarian stimulation characterized by a wide spectrum of clinical and laboratory manifestations. It is classified as mild, moderate, or severe according to the degree of abdominal distention, ovarian enlargement, and respiratory, hemodynamic, and metabolic complications.
Partial or complete rotation of the ovarian vascular pedicle that causes obstruction to ovarian blood flow, potentially leading to necrosis of ovarian tissue.
(OI) Pharmacologic treatment of women with anovulation or oligo-ovulation with the intention of inducing normal ovulatory cycles.
Fetal or neonatal death occurring during late pregnancy (at 20 completed weeks of Gestational age GA and later), during childbirth, or up to 7 completed days after birth.
An acronym for percutaneous epididymal sperm aspiration.
A live birth or stillbirth that takes place after 42 completed weeks of gestational age.
Preimplantation genetic diagnosis
(PGD) Analysis of polar bodies, blastomeres, or trophectoderm from oocytes, zygotes, or embryos for the detection of specific genetic, structural, and/or chromosomal alterations.
Preimplantation genetic screening
(PGS) Analysis of polar bodies, blastomeres, or trophectoderm from oocytes, zygotes, or embryos for the detection of aneuploidy, mutation, and/or DNA rearrangement.
A live birth or stillbirth that takes place after at least 20 but before 37 completed weeks of gestational age.
(PNT) The pro-nucleus is the nucleus of a sperm or an egg cell during the process of fertilisation after the sperm enters the egg, but before they fuse. PNT involves removing the pro-nuclei (nuclear material) from a newly fertilized egg that has unhealthy mitochondria. The pro-nuclei are then transferred into a donated embryo, with healthy mitochondria, that has had its own, original pro-nuclei removed.
Recurrent spontaneous abortion/miscarriage
The spontaneous loss of two or more clinical pregnancies.
Surgical procedures performed to diagnose, conserve, correct, and/or improve reproductive function.
Severe ovarian hyperstimulation syndrome
Severe OHSS is defined to occur when hospitalization is indicated. (See definition of ovarian hyperstimulation syndrome.)
Small for gestational age
Birth weight less than 2 standard deviations below the mean or less than the 10th percentile according to local intrauterine growth charts.
Sperm recipient cycle
An ART cycle in which a woman receives spermatozoa from a donor who is not her partner.
The spontaneous loss of a clinical pregnancy before 20 completed weeks of gestational age (18 weeks after fertilization) or, if gestational age is unknown, the loss of an embryo/fetus of less than 400 g.
See Gestational carrier.
An acronym for testicular sperm aspiration.
An acronym for testicular sperm extraction.
Total delivery rate with at least one live birth
The estimated total number of deliveries with at least one live born baby resulting from one initiated or aspirated ART cycle including all fresh cycles and all frozen-thawed ART cycles. This rate is used when all of the embryos—fresh and/or frozen-thawed—have been used from one ART cycle. Note: The delivery of a singleton, twin, or other multiple pregnancy is registered as one delivery.
Vanishing sac(s) or embryo(s)
Spontaneous disappearance of one or more gestational sacs or embryos in an ongoing pregnancy, documented by ultrasound.
Very low birth weight
Birth weight less than 1,500 g. (More? Birth-Weight)
Very preterm birth
A live birth or stillbirth that takes place after 20 but before 32 completed weeks of gestational age.
An ultra-rapid cryopreservation method that prevents ice formation within the suspension which is converted to a glass-like solid.
A diploid cell resulting from the fertilization of an oocyte by a spermatozoon, which subsequently divides to form an embryo.
Zygote intrafallopian transfer
(ZIFT) A procedure in which zygote(s) is/are transferred into the fallopian tube.
- Zegers-Hochschild F, Adamson GD, de Mouzon J, Ishihara O, Mansour R, Nygren K, Sullivan E & Vanderpoel S. (2009). International Committee for Monitoring Assisted Reproductive Technology (ICMART) and the World Health Organization (WHO) revised glossary of ART terminology, 2009. Fertil. Steril. , 92, 1520-4. PMID: 19828144 DOI.
- Zegers-Hochschild F, Adamson GD, de Mouzon J, Ishihara O, Mansour R, Nygren K, Sullivan E & van der Poel S. (2009). The International Committee for Monitoring Assisted Reproductive Technology (ICMART) and the World Health Organization (WHO) Revised Glossary on ART Terminology, 2009. Hum. Reprod. , 24, 2683-7. PMID: 19801627 DOI.
- Chen T, Bian Y, Liu X, Zhao S, Wu K, Yan L, Li M, Yang Z, Liu H, Zhao H & Chen ZJ. (2017). A Recurrent Missense Mutation in ZP3 Causes Empty Follicle Syndrome and Female Infertility. Am. J. Hum. Genet. , 101, 459-465. PMID: 28886344 DOI.
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- World Health Organization WHO - ART terminology (2009) PDF
- International Committee Monitoring Assisted Reproductive Technologies ICMART
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Cite this page: Hill, M.A. (2021, April 13) Embryology Assisted Reproductive Technology - Glossary. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Assisted_Reproductive_Technology_-_Glossary
- © Dr Mark Hill 2021, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G