The International Glossary on Infertility and Fertility Care

The following glossary was developed in 2017 by a global panel of more than 100 multidisciplinary experts, professional organisations, and patient representatives to provide consensus agreement on 283 items and definitions. Published in Fertility and Sterility (FNS) and Human Reproduction (HR).

A printable version of the 2017 Glossary and more information on the methodology, and a list of previous compiled glossaries can be found here.




Recipient (ART)

A person or couple who receives donated eggs, sperm or embryos for the purposes of initiating a pregnancy with the intention of becoming a legally recognized parent.

Recipient ART cycle

An ART cycle in which a woman receives zygote(s) or embryo(s) from donor(s) or a partner.

Recurrent spontaneous abortion/miscarriage

The spontaneous loss of two or more clinical pregnancies prior to 22 completed weeks of gestational age.

Reproductive surgery

Surgical procedures performed to diagnose, conserve, correct and/or improve reproductive function in either men or women. Surgery for contraceptive purposes, such as tubal ligation and vasectomy, are also included within this term.

Retrograde ejaculation

A condition that causes the semen to be forced backward from the ejaculatory ducts into the bladder during ejaculation.



The surgical removal of an entire Fallopian tube.

Salpingitis isthmica nodosa (SIN)

A nodular thickening of the proximal Fallopian tube (where the tubes join the uterus), which can distort or occlude the tubes and increase the risk of ectopic pregnancy and infertility.


A surgical procedure in which an opening is made in the Fallopian tube either to remove an ectopic pregnancy or open a blocked fluid-filled tube (hydrosalpinx).

Secondary female infertility

A woman unable to establish a clinical pregnancy but who has previously been diagnosed with a clinical pregnancy.

Secondary involuntary childlessness

A condition in a person with a child wish, who has previously delivered a live child, or is or has been a legal or societally-recognized parent to a child. A major cause of secondary involuntary childlessness is infertility.

Secondary male infertility

A man who is unable to initiate a clinical pregnancy, but who had previously initiated a clinical pregnancy.

Semen analysis

A description of the ejaculate to assess function of the male reproductive tract. Characteristic parameters include volume, pH, concentration, motility, vitality, morphology of spermatozoa and presence of other cells.

Semen liquefaction

The process whereby proteolytic enzymes degrade proteins causing seminal plasma to liquefy.

Semen viscosity

The description of the relative fluidity of seminal plasma.

Semen volume

The amount of fluid in an ejaculate.


The fluid at ejaculation that contains the cells and secretions originating from the testes and sex accessory glands.

Seminal plasma

The fluids of the ejaculate.

Sertoli cell

The non-germinal cell type in the seminiferous tubule that mediates the actions of testosterone and FSH in the testis, provides nutrients and proteins to the developing spermatogenic cells, creates the blood-testis barrier, and secretes Mullerian-inhibiting hormone.

Sertoli cell-only syndrome

A condition in which only Sertoli cells line the seminiferous tubules with usually a complete absence of germ cells; also referred to as germ cell aplasia. Spermatogenesis in isolated foci can be observed in rare cases.

Severe ovarian hyperstimulation syndrome (OHSS)

A systemic response as a result of ovarian stimulation interventions that is characterized by severe abdominal discomfort and/or other symptoms of ascites, hemoconcentration (Hct > 45) and/or other serious biochemical abnormalities requiring hospitalization for observation and/or for medical intervention (paracentesis, other).

Single embryo transfer (SET)

The transfer of one embryo in an ART procedure.


A cryopreservation procedure in which the temperature of the cell(s) is lowered in a step-wise fashion, typically using a computer controlled rate, from physiological (or room) temperature to extreme low temperature.

Small for gestational age

A birth weight less than the 10th centile for gestational age. When reporting results the reference criteria should be specified. If gestational age is unknown, the birth weight should be registered.

Sperm bank

Repository of cryopreserved sperm stored for future use.

Sperm concentration

The (measure of the) number of spermatozoa in millions per 1 ml of semen.

Sperm density

A measure of the mass/volume ratio (specific gravity) for spermatozoa.

Sperm isolation

A procedure that involves the separation of sperm through centrifugation and resuspension in culture media. It can be used to remove seminal plasma and infectious agents before IUI and ART procedures. This procedure has been shown to be effective in the removal of HIV. It may also be effective in removing other infectious particles but clinical safety and efficacy have to be established for each particular infection. This term is sometimes referred to as ‘sperm washing’.

Sperm motility

The percentage of moving spermatozoa relative to the total number of spermatozoa.

Sperm recipient cycle

A MAR cycle in which a woman receives spermatozoa from a person who is not her sexually intimate partner. In the case of ART registry data, a sperm recipient cycle would only include data from cycles using ART procedures.

Sperm vitality

The percentage of live spermatozoa relative to the total number of spermatozoa.

Spermatogenic arrest

Failure of germ cells to progress through specific stages of spermatogenesis at onset or during meiosis.


The mature male reproductive cell produced in the testis that has the capacity to fertilize an oocyte. A head carries genetic material, a midpiece produces energy for movement, and a long, thin tail propels the sperm.

Spontaneous abortion/miscarriage

The spontaneous loss of an intra-uterine pregnancy prior to 22 completed weeks of gestational age.

Spontaneous reduction/vanishing sac(s)

The spontaneous disappearance of one or more gestational sacs with or without an embryo or fetus in a multiple pregnancy documented by ultrasound.


A permanent state of infertility.


The death of a fetus prior to the complete expulsion or extraction from its mother after 28 completed weeks of gestational age. The death is determined by the fact that, after such separation, the fetus does not breathe or show any other evidence of life, such as heartbeat, umbilical cord pulsation, or definite movement of voluntary muscles. Note: It includes deaths occurring during labor.

Stillbirth rate

The number of stillbirths per 1000 total births (stillbirths plus live births).


A term that should be used interchangeably with infertility.


The process during which the female and male pronuclei fuse.



A reduced percentage of morphologically normal sperm in the ejaculate below the lower reference limits. When reporting results, the reference criteria should be specified.

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.


The process of raising the temperature of slow-frozen cell(s) from the storage temperature to room/physiological temperature.

Time to pregnancy (TTP)

The time taken to establish a pregnancy, measured in months or in numbers of menstrual cycles.

Time-lapse imaging

The photographic recording of microscope image sequences at regular intervals in ART, referring to gametes, zygotes, cleavage-stage embryos or blastocysts.

Total delivery rate with at least one live birth

The total number of deliveries with at least one live birth resulting from one initiated or aspirated ART cycle, including all cycles in which fresh and/or frozen embryos are transferred, including more than one delivery from one initiated or aspirated cycle if that occurs, until all embryos are used. Notes: The delivery of a singleton, twin or other multiple pregnancy is registered as one delivery. In the absence of complete data, the total delivery rate is often estimated.

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).

Total sperm count

The calculated total number of sperm in the ejaculate (semen volume multiplied by the sperm concentration determined from an aliquot of semen).

Traditional gestational carrier

A woman who donates her oocytes and is the gestational carrier for a pregnancy resulting from fertilization of her oocytes either through an ART procedure or insemination. This replaces the term ‘traditional surrogate.’


An abnormal number of chromosome copies in a cell characterized by the presence of three homologous chromosomes rather than the normal two. The majority of human embryos with trisomies are incompatible with life.


Cells forming the outer layer of a blastocyst that have the potential to develop into the placenta and amniotic membranes.

Tubal pathology

Tubal abnormality resulting in dysfunction of the Fallopian tube, including partial or total obstruction of one or both tubes (proximally, distally or combined), hydrosalpinx and/or peri-tubal and/or periovarian adhesions affecting the normal ovum pick-up function. It usually occurs after pelvic inflammatory disease or pelvic surgery.


Unexplained infertility

Infertility in couples with apparently normal ovarian function, Fallopian tubes, uterus, cervix and pelvis and with adequate coital frequency; and apparently normal testicular function, genito-urinary anatomy and a normal ejaculate. The potential for this diagnosis is dependent upon the methodologies used and/or those methodologies available.


The condition in a cell resulting from loss of a single chromosome yielding a single copy of that particular chromosome rather than the normal two. The majority of unisomies in human embryosare incompatible with life.


Vaginal insemination

A procedure whereby semen, collected from a non-lubricated condom or similar method, is deposited into the vaginal cavity of a female. An intervention that can be self-administered by a woman attempting pregnancy.


A venous enlargement in the testicular pampiniform plexus.


Procedure to occlude or remove part of the internal spermatic vein in situations in which it has expanded into a varicocele.


Procedure to occlude the vas deferens. It is usually carried out bilaterally in order to secure sterilization.

Very low birth weight

Birth weight less than 1500 g.


The description of the relative fluidity of the semen.


An ultra-rapid cryopreservation procedure that prevents ice formation within a cell whose aqueous phase is converted to a glass-like solid.

Voluntary childlessness

A condition describing a person who does not have or has not had a child wish and does not have any biologically, legally or societally-recognized children.


Warming (cells)

The process of raising the temperature of a vitrified cell or cells from the storage temperature to room/physiological temperature.


Y-chromosome microdeletions

Missing segments of the genetic material on the Y-chromosome that are associated with abnormal spermatogenesis.


Zona pellucida

The glycoprotein coat surrounding the oocyte.


A single cell resulting from fertilization of a mature oocyte by a spermatozoon and before completion of the first mitotic division.

Zygote intrafallopian transfer (ZIFT)

An ART procedure in which one or more zygotes is transferred into the Fallopian tube.