Fertility A-Z


Welcome to my glossary of fertility terms. This has taken me a long time to put together but was something that I felt was important to do as I am consistently asked, “what do all these fertility terms mean?!”

It can be a minefield, especially if you are at the start of your fertility journey. I am updating the glossary frequently so if you notice something missing please do email me at info@thefertilitykitchen.co.uk and I will add it. Also check out my list of fertility acronyms which you will almost certainly need to refer to if you join any online support communities. I really hope this helps you as you navigate your fertility journey.



Abandoned cycle: when an IVF cycle is cancelled before egg collection

Adhesions: scar tissue, see Asherman’s Syndrome

Agglutination: sperm are clumping together, which may prevent forward motion and stop the sperm swimming up through the cervix

Amnion: the inner membrane forming the sac in which the embryo develops

Amniotic fluid: the fluid filling the cavity between the embryo and the amnion

Andrology: the study of fertility in men

Anti-mullerian hormone (AMH): a hormone produced by cells in the ovaries, the levels of which are thought to reflect the size of the remaining egg supply or “ovarian reserve”

Aneuploidy: a term used to describe an embryo that either has too many or too few chromosomes

Aneuploidy screening: see PGS

Antagonistic IVF: see Mild IVF

Antral follicles: the small follicles that develop in response to the drugs given during IVF treatment

Antral follicle count: the number of antral follicles present in the ovaries, when counted on days 2-5 of your menstrual cycle

Arcuate womb: the arcuate womb looks very like a normal womb but it has a dip at the top. Arcuate womb does not increase the risk of preterm birth or first trimester miscarriage but it does increase your risk of second trimester miscarriage

Artificial egg activation: when a sperm meets an egg, it triggers a process called ‘egg activation’ which starts off the process of embryo development, while at the same time allowing only one sperm to fertilise the egg. If the egg doesn’t activate, then it won’t develop.

Egg (or oocyte) activation may be stimulated by chemicals called calcium ionophores. These chemicals can be added to the embryo in the lab

Artificial insemination: see IUI

Asherman’s Syndrome: an acquired uterine condition characterised by the formation of adhesions (scar tissue) inside the uterus and/or the cervix

Assisted hatching: before an embryo can attach to the wall of the womb it has to break out or ‘hatch’ from its outer layer (the zona pellucida), thinning this outer layer may help embryos to hatch, which may increase the chance of pregnancy

Assisted reproduction technology (ART): collective name for all techniques used to artificially assist women to carry a baby, including IVF and ICSI

Asthenozoospermia: reduced sperm motility

Azoospermia: absence of sperm from the seminal fluid



Balanced inversion: a chromosome abnormality. A piece of chromosome breaks off, turns over, and reattaches itself back to the same chromosome

Balanced translocation: a chromosome abnormality. A piece of chromosome breaks off and attaches itself to a different chromosome

Basal body temperature (BBT): your body temperature at rest

Baseline scan: an ultrasound scan during IVF to check that down-regulation has been achieved, before the stimulation phase can begin. The scan should confirm that there are no cysts on the ovaries and that the uterine lining is thin

Beta hCG: a quantitative hCG test that measures the amount of hCG actually present in the blood (pregnancy blood test)

Bicornuate uterus: a heart-shaped womb. Women with a bicornuate womb have no extra difficulties with conception or in early pregnancy, but there is a slightly higher risk of miscarriage and preterm birth

Blastocyst: an embryo that has developed for five to six days after fertilisation. A blastocyst has a large number of cells and consists of two distinct cell types

Blastocyst culture: embryos are matured further (beyond ‘day 3’) in laboratory conditions before transfer. in natural conception, embryos would not normally reach the uterus until day 5; this is called the blastocyst stage of development

Blastocyst transfer: transfer of an embryo that has developed for five to six days after fertilisation

Blastomere: a biopsy from a blastocyst

Bromocriptine: a drug used when women who produce too much of the prolactin hormone, a condition called hyperprolactinemia. Prolactin is produced by the pituitary gland in the brain and too much of it can reduce levels of oestrogen in the body, making ovulation difficult. Bromocriptine increases levels of dopamine in the brain, which helps to reduce levels of prolactin production and return ovulation to normal

Buserelin: a drug used in IVF that acts on the pituitary gland to down-regulate the body’s own hormone production, and encourage favourable reaction to other hormone drugs in IVF treatment



Cabergoline: a drug used in women who produce too much of the prolactin hormone, a condition called hyperprolactinemia. Prolactin is produced by the pituitary gland in the brain and too much of it can reduce levels of oestrogen in the body, making ovulation difficult. Cabergoline increases levels of dopamine in the brain, which helps to reduce levels of prolactin production and return ovulation to normal

Capacitation: a process that occurs to sperm, which gives them the ability to penetrate and fertilise an egg, as they pass through the female genital tract. This can be mimicked in a culture medium

Cervical fluid/mucus: secretions surrounding the cervix; the amount and texture of which changes during ovulation

Chemical pregnancy: a very early miscarriage. The women tests positive for pregnancy but miscarries before anything can be seen in the uterus on ultrasound. Therefore the only evidence that she was ever pregnant is the chemical reaction that caused the pregnancy test to turn positive

Cleavage stage embryos: two to three-day old embryos

Clomifene citrate (Clomid): a fertility drug that stimulates the production of one or more follicles, therefore increasing the chances of pregnancy

Clotting (thrombophilia) screen: small clots in the blood have been identified as a possible cause for a pregnancy failing to progress. In some cases this can be treated with injections to thin the blood

Controlled ovarian hyperstimulation (COH): the use of drugs to produce multiple mature follicles

Cryopreservation: freezing of embryos. See also vitrification



DNA fragmentation: assessing the degree of damage to sperm DNA to help identify couples who would benefit from ICSI treatment

Donor insemination (DI): uses a sperm from a donor to help the woman become pregnant

Down regulation: first stage of an IVF treatment cycle. Medication is taken as a daily injection or nasal spray to suppress natural hormone production



Ectopic pregnancy: a pregnancy that develops outside of the womb, typically in the fallopian tubes

Egg collection: a stage of IVF, performed under sedation, where eggs are collected from each ovary under ultrasound guidance

Egg vitrification: rapid freezing of eggs immediately after collection. Used for fertility preservation or egg donation

Elective freeze all cycles: elective freeze all cycles involve creating embryos using IVF or ICSI and then freezing all of them so no embryos are transferred in the ‘fresh’ cycle. The embryos are thawed a few months later and transferred to the woman’s womb as part of a frozen embryo transfer (FET) cycle

Elective single embryo transfer (eSET): if you have more than one good quality embryo available, it is now best practice for most women to have only one embryo put back in the womb and freeze the others. This is to reduce the chance of a multiple birth

Embryo: formed when the egg and sperm meet, the embryo develops into the foetus

EmbryoGlue: an IVF treatment add-on. EmbryoGlue contains a natural substance called hyaluronan, which may improve the chance of the embryo implanting in the womb. It is added to the solution (culture medium) in the dish in which the embryos are kept before being transferred to the woman

EmbryoScope: see time-lapse imaging

Embryo transfer: takes place after eggs have been collected and fertilised in the laboratory. Between one and three of the best quality embryos are selected and then transferred to the woman’s womb

Embryo vitrification: rapid freezing of embryos to prevent the formation of ice crystals, helping to preserve cell quality and improve chances of success on thawing. If OHSS is suspected then it may be decided to vitrify all of the embryos from a treatment cycle and postpone embryo transfer to a later date. Vitrification is used to freeze surplus good quality embryos for future use

Endocrinology: the study of hormones

Endometrial Receptivity Array: a small amount of tissue from the womb lining can be sampled and analysed for the presence of over 200 genes known to be associated with implantation

Endometrial scratch: an IVF treatment add-on. Endometrial scratching is carried out before IVF and is intended to correct problems with the womb lining. During the procedure the lining of the womb (the endometrium) is ‘scratched’ using a small sterile plastic tube. The theory is that this procedure triggers the body to repair the site of the scratch, releasing chemicals and hormones that make the womb lining more receptive to an embryo implanting. Some also suggest the treatment may activate genes that make the womb lining more receptive to an embryo implanting.

Endometriosis: a condition where the type of cells that line the uterus (womb) are found elsewhere in the body, e.g. the ovaries or elsewhere in the pelvis

Endometrium: the lining of the womb



Fibroid: a benign muscle growth in the wall of the womb

Follicle: fluid sac that surrounds each egg produced by the ovaries. These are counted and measured via an ultrasound scan during the stimulation phase of an IVF treatment cycle

Follicle-stimulating hormone (FSH): a hormone produced by the pituitary gland that stimulates the growth of egg follicles

Frozen Embryo Transfer (FET): a cycle in which frozen embryo/s from a previous fresh IVF cycle are thawed and then transferred back into the woman’s uterus

FET-HRT: Stimulated frozen embryo transfer. Medication is taken to prevent ovulation and to prepare the womb for embryo transfer. A scan on day 8-10 confirms endometrial thickness, once at the right thickness arrangements are made for embryo transfer



Gamete intra-fallopian transfer (GIFT): instead of the eggs being fertilised “in vitro” in the laboratory, the healthiest eggs and sperm are placed together in the woman’s fallopian tubes. Fertilisation therefore takes place in the body, as it would if conception had occurred naturally

Genetic screening: this is used to learn more about embryos before they are transferred, enabling selection of the embryos most likely to implant

Gonadotrophins: in women these hormones stimulate the ovaries to produce a follicle, which contains an egg. They are lutenising hormone (LH) and follicle stimulating hormone (FSH). See also human menopausal gonadotrophin (HMG), In men, gonadotrophins stimulate the release of testosterone which supports

Gonadotrophin exogenous oestrogen and progesterone (GEEP): a combination of drugs used to stimulate a menstrual cycle prior to the replacement of frozen embryos. Oestrogen and progesterone are produced naturally in the body

Gonal-f: a fertility drug used in IVF to stimulate the growth of egg follicles. It contains FSH only



Harmony Prenatal Test: a prenatal screening test that measures fetal DNA present in the mother’s blood and is available from 10 weeks gestation. The test screens for Down syndrome (Trisomy 21), Edwards’ syndrome (Trisomy 18), Patau syndrome (Trisomy 13) and the foetal sex if requested

Human chorionic gonadotrophin (hCG): a hormone produced by the placenta after implantation and is the hormone that is detected by home pregnancy tests

Human Fertilisation & Embryology Authority (HFEA): the UK’s independent regulator of fertility treatment and research using human embryos. A good place to start if you are struggling to conceive

Human menopausal gonadotrophin (HMG): general name for the drug used in IVF to stimulate the growth of egg follicles. There are many different trade names, e.g. Gonal-F, Menopur, Puregon. They contain FSH alone, or FSH and LH.

Hydrosalpinx: a blocked, dilated, fluid-filled fallopian tube usually caused by a previous tubal infection

Hysteroscopy: an operation where a thin telescope is inserted through the neck of the womb into the cavity of the womb. Small polyps and fibroids can be removed during this procedure

Hyperprolactinemia: a condition where too much of the hormone prolactin is secreted. Prolactin is produced by the pituitary gland in the brain and too much of it can reduce levels of oestrogen in the body, making ovulation difficult. See also bromocriptine and cabergoline



Immune screen: increased levels of uterine natural killer cells (white cells) and autoantibodies (antibodies attacking specific organs) have been suggested as a cause for repeated failure of cycles. The use of steroids, intralipids and other drugs to suppress the immune system and to help a pregnancy develop are controversial. More clinical trials are needed to understand the ways in which the immune system affects pregnancy and which treatments might benefit which women

Intracytoplasmic Sperm Injection (ICSI): a single sperm is injected directly into each egg. ICSI enables fertilisation to happen when there are very few sperm available

Intralipids: intralipid infusions are a sterile fat emulsion containing soybean oil, egg yolk, glycerin and water, which is administered by injection. According to the Royal College of Obstetricians and Gynaecologists there is no rationale for their use in fertility treatment

Intrauterine culture: an IVF treatment add on that allows the early stages of embryo development to take place within the woman’s womb. The fertilised eggs are placed in an intrauterine culture device, which is inserted into the woman’s womb. The device stays in place for several hours during the initial stages of embryo development

Intrauterine insemination (IUI): the highest quality sperm are selected and injected into the uterus where they are left to fertilise the eggs naturally

Intravenous immunoglobulin (IVIg): treatment offered as part of reproductive immunology

In-Vitro Fertilisation (IVF): the fertilisation of egg/s outside the body. The treatment can be performed using your own eggs and sperm, or using either donated sperm or donated eggs, or both

In-Vitro Maturation (IVM): Eggs are removed from your ovaries when they are still immature. They are then matured in a laboratory before being fertilised



Karyomapping: see pre-implantation genetic diagnosis (PGD)



Laparoscopy: an investigation of the woman’s reproductive system using a thin telescope inserted through the navel. It magnifies the view of the fallopian tubes, ovaries and uterus. the procedure is used to diagnose certain causes of infertility such as blocked tubes, endometriosis or adhesions (scar tissue)

Laser-assisted hatching: (see also assisted hatching) A laser is used to weaken an area of the zona pellucida (embryo’s shell) with the aim of improving the chances of implantation. It is carried out immediately before embryo transfer. A laser is considered to be the safest and most accurate method

Lutenising hormone (LH): a hormone produced by the pituitary gland that controls ovulation. The ‘LH surge’ indicates that ovulation will occur in about 36 hours. The surge is stimulated by an increase of oestrogen in the blood, produced by the growing egg follicle



Maternal spindle transfer (MST): a technique for mitochondrial donation where the patient’s nuclear genetic material will be removed from her eggs and transferred into donated eggs which have had their nuclear genetic material removed. See also mitochondrial donation treatment

Menopur: see human menopausal gonadotrophin (HMG)

Metformin: metformin isn’t technically a fertility drug; it’s a drug used in the treatment of people with diabetes. However it can be prescribed to some women with polycystic ovaries who aren’t ovulating properly because of abnormal insulin levels in the body. Women with PCOS can develop insulin resistance, which means their body stops reacting to normal insulin levels. To compensate, the body will produce more insulin than it needs and this can lead to high androgen (male hormone) levels which affect ovulation. Metformin reduces insulin in the body to normal levels, allowing ovulation to return to normal.

Microsurgical epididymal sperm aspiration (MESA): a treatment to surgically extract sperm (see also surgical sperm retrieval). It involves examining the epididymis under an operating microscope and taking fluid samples for further examination to see if there are any sperm

MicroTESE: a treatment to surgically extract sperm (see also surgical sperm retrieval). It involves examining the testicle with an operating microscope to find areas (tubules) where sperm are being made. The promising areas are taken out and sperm extracted if possible. Many experts believe that MicroTESE has the best chance of recovering sperm from men with non-obstructive azoospermia

Mild IVF: a lower dose of fertility drugs are given over a shorter period of time than with conventional IVF. This reduces treatment time by about two weeks and a lot of the unpleasant side effects from the drugs can be avoided. Although there are still some health risks from mild stimulation IVF they tend to be less common and less serious than with standard IVF

Missed miscarriage (MMC): when the foetus dies but the body doesn’t recognise the loss or expel the pregnancy tissue. Consequently the woman may continue to experience signs of pregnancy

Mitochondrial donation treatment: a technique that can be used by people with severe mitochondrial disease to avoid passing the condition onto their children. Eggs or embryos are created using the nuclear genetic material of the patient and healthy donated mitochondria. There are two techniques by which this can be achieved (see maternal spindle transfer and pronuclear transfer). Every case of mitochondrial donation treatment must be approved by the HFEA to ensure that it is carried out in a legal and ethical way. There are three main mitochondrial disease centres in the UK; in London, Oxford and Newcastle

Motility: how well sperm move

Myomectomy: surgical removal of fibroids from the uterus



Natural IVF: involves no fertility drugs at all. The one egg released as part of a normal monthly cycle is taken and fertilised with sperm. IVF treatment is then continued as normal. Because the ovaries aren’t stimulated there is no need for a break between IVF cycles, which means another cycle can commence straight away if unsuccessful. The risk of multiple pregnancy (twins or triplets) is lower than standard IVF and the risks and side effects of fertility drugs can be avoided. Birth rates are much lower than for standard IVF. The latest statistics show that the birth rate for all ages is around 6%

Nuchal test: (see also Harmony test) a prenatal scan that can identify chromosomal abnormalities associated with conditions such as Down Syndrome



Oligoasthenoteratozoospermia: low sperm count, with a high percentage of slow-moving and abnormal sperm

Oligozoospermia: low sperm count

Oocytes: eggs

Orgalutran: a drug used to suppress ovulation

Ovarian hyper-stimulation syndrome (OHSS): a potentially dangerous overreaction to fertility drugs, when too many follicles develop in the ovaries. The symptoms include lower abdominal pain, swelling of the abdomen, nausea, vomiting and sometimes shortness of breath. Treatment involves bed rest with increased fluid intake and in rare cases hospitalisation and intravenous fluids

Ovarian reserve: a woman’s ‘store’ of eggs. Women are born with their lifetime supply of eggs in their ovaries and they are gradually used up as women menstruate and age until very few eggs are left. The menopause then begins and periods cease. The reserve of eggs falls particularly fast in women over the age of 40. Fertility also reduces with age falling to low levels ten years before the menopause

Ovarian tissue freezing: a fertility preservation option for women who are unable to freeze their eggs and for younger girls who haven’t started ovulating

Ovary (ovaries): the organ/s that produce eggs, women usually have two

Ovulation: the release of an egg from the ovary mid-way through the menstrual cycle; the optimal time for fertilisation

Ovulation predictor kits (OPKs): these measure the presence of LH in your urine. The ‘LH surge’ indicates that ovulation will occur in about 36 hours



Polycystic Ovarian Syndrome (PCOS): an endocrine disorder whereby polycystic ovaries are one of an array of possible symptoms caused by an underlying hormone imbalance. The term polycystic ovaries describes ovaries that contain many small ‘cysts’ (about twice as many as in normal ovaries), usually no bigger than 8 millimetres each, located just below the surface of the ovaries. The ‘cysts’ in polycystic ovaries are not true cysts. They are not full of liquid, they do not get bigger or burst, they do not require surgical removal and do not lead to ovarian cancer. They are actually follicles that have not matured to be ovulated

Polyp: a benign growth of the lining of the womb (endometrium)Pre-implantation genetic diagnosis (PGD): enables people with an inheritable condition in their family to avoid passing it on to their children. It involves checking the genes and/or chromosomes of embryos created through IVF

Pre-implantation genetic diagnosis (PGD): this is used when a serious genetic disease could be passed from parent to child. There are two techniques: karyotyping, and conventional pre-implantation genetic diagnosis. Karyomapping, unlike conventional PGD, can screen embryos for chromosomal abnormalities as well as a certain genetic mutation, thus increasing the likelihood of a healthy on-going pregnancy. Conventional PGD is used where the mutation is new and not present in either of the parents, or where DNA is unobtainable from other family members who have the same genetic mutation.

Pre-implantation genetic screening (PGS): this involves checking the chromosomes of embryos conceived by IVF or ICSI for common abnormalities. Chromosomal abnormalities are a major cause of the failure of embryos to implant, and of miscarriages. They can also cause conditions such as Down syndrome

Pre-implantation tissue typing (PTT): a type of embryo testing, PTT is a technology which can be used in some cases to help children with very serious blood disorders, such as beta thalassaemia, Fanconi’s anaemia and Diamond Blackfan anaemia. Also known as ‘saviour siblings’. The best available treatment for children with these illnesses usually involves a transfusion of stem cells from a tissue-matched donor, ideally a close relative. Where a close relative isn’t available, parents can choose to have another child and use PTT treatment to only select embryos that are an exact tissue match to their older sibling. It’s for this reason that PTT is sometimes referred to as ‘saviour siblings’ technology

Premature menopause: when periods stop before the age of 40 and a woman can no longer get pregnant. The cause can be natural, or it can be due to disease, surgery, chemotherapy or radiation

Premature ovarian insufficiency (POI): also known as primary ovarian insufficiency, this is a loss of normal ovarian function before the age of 40. Some women still have occasional periods and may get pregnant. The cause is usually unknown

Progesterone: a hormone secreted in the body that helps prepare the uterus for implantation of the embryo. Progesterone can be measured in the blood stream and showed a marked increase after ovulation has occurred

Pronuclear transfer (PNT): a technique for mitochondrial donation where the patient’s eggs will be fertilised with sperm in a lab to create embryos. The nuclear genetic material within each embryo will then be transferred into embryos created using donated eggs and sperm from the sperm provider. The nuclear genetic material will have been removed from the donated eggs. See also mitochondrial donation treatment

Puregon: a fertility drug used in IVF to stimulate the growth of egg follicles



Reproductive immunology: is concerned with the way a woman’s immune system reacts if she becomes pregnant



Saviour siblings: see pre-implantation tissue typing (PTT)

Septate womb: the septate womb has a wall of muscle down the centre splitting the space in two. Women with septate wombs are more likely to have difficulties with conception. There is also an increased risk of first trimester miscarriage and preterm birth

Sperm: the male reproductive cell, produced in the testes

SpermSlow: hyaluranon is a naturally occurring substance present in follicles, tubes and cavity of the womb. Hyaluranon may help to isolate mature sperm for use in ICSI (intracytoplasmic sperm injection) cycles helping to increase fertilisation rates

Subseptate womb: where there is a wall of muscle part-way down the centre of the womb. Women with subseptate wombs are more likely to have difficulties with conception. There is also an increased risk of first trimester miscarriage and preterm birth

Surgical sperm retrieval: sperm is collected via surgery. Some men are manufacturing sperm in their testes, but it is not present in ejaculate when the semen is analysed. This can be caused by a blockage, or reduced sperm production. In these cases, sperm can be collected via surgery. This method is also used to collect sperm for men who have previously had a vasectomy, or a failed vasectomy reversal. Sperm is either collected by aspiration through the skin, aspiration through testicular skin or extraction from a testicular tissue sample (biopsy)

Super-ovulation: the release of several eggs from the ovary as a result of fertility treatment

Surrogacy: involves a woman becoming pregnant and giving birth to a baby for a couple who want to have a child but can’t. The surrogate is the woman who carries and gives birth to the child for the intended parents (sometimes called the commissioning couple)



TNF blocking agents: drugs that block the effect of TNF (tumour necrosis factor), a chemical produced by immune system cells, such as NK cells, which help immune cells reach the source of infections by promoting inflammation. They stop inflammation but make the attack on infection less effective

Teratozoospermia: high levels of abnormal sperm

Testicular Sperm Aspiration (TESA): a treatment to surgically extract sperm (see also surgical sperm retrieval). A fine syringe is inserted into either the epididymis or the testicle to extract the sperm. It’s a quick and relatively painless procedure that’s usually performed under local anaesthetic

Testicular Sperm Extraction (TESE): a treatment to surgically extract sperm (see also surgical sperm retrieval). It involves making an incision into the testicle to take a small sample (biopsy) away from which sperm can hopefully be recovered.  TESE can be performed under local or general anaesthetic. Multi-site TESE (where multiple samples are taken from different areas) is usually performed under general anaesthetic

Testicular tissue freezing: a specialist technique to preserve the fertility of men who do not produce viable sperm in their ejaculate (azoospermia)

Time-lapse imaging: in IVF time-lapse imaging is used to help select the embryos most likely to successfully develop into a baby



Ultrasound: modern diagnostic equipment that works by aiming ultrasonic sound waves and displaying visual interpretation of the echoes on a screen. Vaginal ultrasound is an internal use of this equipment to provide a clear view of the ovaries, follicles, fallopian tubes and womb. Ultrasound is also used in pregnancy to provide a diagnostic picture of the foetus

Unicornuate womb: a rare condition where the womb is half the size of a normal womb because one side failed to develop. There is an increased risk of ectopic pregnancy, late miscarriage or preterm birth.Women with a unicornate womb can often conceive, although it is also true to say that the prevalence of unicornuate uterus is higher in women who are infertile

Uterus: the womb

Uterus didelphys: more commonly known as a double uterus, this is a rare congenital abnormality. In a female foetus, the uterus begins as two small tubes, as the foetus develops the tubes join to create one larger, hollow organ; the uterus. Sometimes the tubes don’t join completely, instead each one develops into a separate structure. A double uterus may have one opening (cervix) into one vagina, or each uterine cavity may have a cervix. In many cases, a thin wall of tissue (septum) runs down the length of the vagina, dividing it into two separate openings


Vaginal ultrasound: see ultrasound

Vas deferens: the tube connecting the testis, where the sperm is made and stored (via the epididymis), to the urethra

Vitrification: rapid freezing of embryos to help prevent the formation of ice crystals. This helps to preserve the quality of the cells and improves the chances of success when they are thawed


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