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A-Z fertility glossary

We have provided a list of terms to help you understand some of the terminology that might be used when you are going through fertility treatment.

Table of contents



The legal process to become the legal parent or parents of a child, which takes away the legal rights of anyone who previously had parental responsibility for the child.

Anti-Müllerian Hormone (AMH)

An AMH test measures levels of anti-müllerian hormone, which corresponds to a person’s egg count.

Artificial insemination

The process by which sperm is directly placed into a woman's cervix, fallopian tubes, or uterus. The most common method is intrauterine insemination (IUI), see below.

Assisted Hatching

The use of acid, lasers or other tools to thin or create a small hole in the zona pellucida of an embryo.

Assisted Reproductive Technology (ART)

Procedures that help unite an egg and sperm outside the body in the laboratory such as IVF.



An embryo that has developed for five to six days after fertilisation.

Blastocyst transfer

An embryo that has reached five or six days of development and is transferred into the uterus.



The opening to the uterus.

Cervical Mucous

A fluid that enhances the transport of the sperm into the endometrial cavity.


Is a healthcare professional who works one-on-one with patients, diagnosing or treating illnesses. A clinician could be a doctor, nurse or a psychologist.

Clomifene citrate (Clomid)

Clomid is a fertility drug used to stimulate the ovaries to produce more eggs. It’s often the first course of treatment for patients with polycystic ovaries but it can also be used by patients who have late or irregular periods.


When an egg is fertilised by sperm and then starts to grow in the womb.


Donor conceived people

Someone that has been conceived as a result of their parent or parents using donor sperm, eggs or embryos.

Donor conception

Donor conception means having a baby using donated sperm, or donated eggs or donated embryos.

Donor Insemination (DI)

Donor insemination is a treatment where donated sperm is placed directly into the womb to fertilise the eggs during fertility treatment.


Ectopic pregnancy

An ectopic pregnancy is when an embryo develops outside of the womb, usually in the fallopian tube.

Egg Collection

A procedure performed to collect the eggs produced from an IVF/ICSI cycle. This can be performed under sedation or a General Anaesthetic.

Egg donation

The donation of eggs to a treatment clinic for other patients to use in their fertility treatment.

Egg freezing

A treatment where a patient has their eggs collected and frozen for future use.

Egg sharing

Egg sharing is when a patient who is already having IVF donates some of their eggs to the clinic where they’re having treatment, usually in return for some free or discounted treatment. This is also sometimes referred to as 'benefits in kind.'


A fertilised egg that has started to develop is known as an embryo until eight weeks of pregnancy, and then a fetus until birth.

Embryo donation

Embryos are donated by patients who have been through IVF treatment and have frozen embryos remaining in storage that they no longer wish to use. These frozen embryos are given for use in the treatment of another person or couple.

Embryo freezing

Couples with good quality embryos they're not ready to use have the option of freezing them to use in the future or to donate.


Embryologists are scientists involved in fertility treatment and reproductive research. They collect eggs, assess, and prepare sperm samples, and inject eggs with sperm. They also do very detailed procedures where they select a single sperm to fertilise an egg.

Embryo transfer

The process of transferring embryos from the culture in which they have been developing in the lab, into the womb.


Endometriosis is a condition where tissue similar to the lining of the womb starts to grow in other places, such as the ovaries and fallopian tubes.


Fallopian tubes

Tubes connected to the uterus and positioned near the ovaries. It is here that fertilisation of the egg and sperm occurs.


Sperm penetrating the egg which can lead to pregnancy.


The ability to conceive a baby and to become pregnant.

Fertility drugs

Fertility drugs can be used in the treatment of some patients who have been trying to get pregnant but have been unable to do so naturally.

Fertility MOT

Fertility MOTs assess your ovarian reserve (the number and quality of eggs) by testing for two hormones: follicle stimulating hormone (FSH) and anti-Müllerian hormone (AMH). The tests can give some indication of how fertile a woman is although the results are not guaranteed.

Fertility preservation

Preserving your fertility involves freezing your eggs, sperm, embryos or reproductive tissue so that you can hopefully have a biological family in the future.

Fertility treatment

See assisted reproductive technology.


Non-cancerous growths that develop in or around the womb. You can have one fibroid or many, and they can be of different sizes. Fibroids are sometimes known as uterine myomas or leiomyomas.


A fluid filled sac in the ovary in which an egg grows and develops.

Follicle-stimulating hormone (FSH)

A gonadotrophic hormone that stimulates the growth of ovarian follicles in the ovary before the release of an egg from one follicle at ovulation. In males it can also stimulate sperm production.

Follicle tracking

A series of ultrasound scans to follow the development of a follicle to see if an egg is developing.

Freeze cycle

A cycle in which a patient has eggs collected with the intention of freezing them for use in future treatment.

Fresh embryo transfer

A fresh embryo transfer is one that occurs soon after egg collection.

Frozen embryo transfer

Embryos frozen for use at a later date or in future cycles.



Male sperm and female eggs.

Genetic testing

If there's a chance that you or your partner could carry a genetic condition, you may be able to get genetic testing done on the NHS. This is a type of test that looks at your genes to see whether you carry a particular condition, and how likely you are to pass it on to your baby. If you're concerned about your family medical history, speak to your GP about genetic testing.


Gonadotrophins are injectable hormones that are used to help stimulate the ovaries to produce eggs before cycles of IVF treatment, or to treat PCOS when Clomid hasn’t worked, they are also used to stimulate the release of testosterone which support sperm production in the testicles.

Gonadotrophins contain follicle-stimulating hormone (FSH), luteinizing hormone (LH) or a combination of both. They can be followed by an injection of human chorionic gonadotrophin (hCG) to trigger the final stage of egg maturation.


Home insemination

Home insemination is when you impregnate yourself at home with donor sperm. We don't recommend this as there can be serious health and legal implications.


A natural occurring chemical produced by the endocrine glands in the body, that circulate in the bloodstream to give an effect on a distant organ or organs. E.g. oestrogen produced by the ovaries and testosterone produced by the testes.

Human chorionic gonadotropin (hCG)

Human Chorionic Gonadotrophin is an injectable hormone that helps the eggs to go through the final stage of maturation, so they are ready for collection. You’ll receive a hCG injection to ‘trigger’ the final stage just before your egg retrieval procedure.

Human Fertilisation and Embryology Authority (HFEA)

The UK wide regulator of fertility treatment and embryo research.

Hysterosalpingo-contrast-ultrasonorgraphy (HyCoSy)

A small amount of dye is injected into the uterus and an ultrasound scan is used to see if the dye has passed through the fallopian tubes, showing the tubes are not blocked.


An x-ray to check your fallopian tubes.


A procedure in which the uterine cavity is visualised by a surgeon. Can help in the diagnosis of fibroids or polyps.



The inability of a couple to achieve a pregnancy after one year of regular unprotected sexual intercourse, or the inability of a woman to carry a pregnancy to live birth.

Intracytoplasmic sperm injection (ICSI)

ICSI can be performed as a part of some IVF cycles. In a standard IVF cycle sperm are mixed with the egg to fertilise it. During an ICSI cycle instead of mixing them together a skilled embryologist will inject a single sperm into the egg to fertilise it.

Intrauterine insemination (IUI)

IUI, also known as artificial insemination, involves sperm being placed directly into the womb. Sperm are sorted and better quality sperm are separated from sperm that are sluggish, non-moving or abnormally shaped, and only the better quality sperm are used for IUI.


A medical procedure that invades (enters) the body, usually by cutting or puncturing the skin or by inserting instruments into the body.

In vitro fertilisation (IVF)

A procedure that involves removing eggs from a woman’s ovaries and fertilising them in the laboratory outside the body. The resulting embryos are then replaced back into the woman’s womb through the cervix.


Kartagener’s Syndrome

This causes problems with sperm tails and requires treatment using ICSI. Sufferers often have poor lung function.


A karyotype is an individual's complete set of chromosomes.


A test to examine chromosomes.



Also known as keyhole surgery is a surgical procedure in which a telescope-like device is inserted through a small incision near the navel to view the pelvic cavity, the ovaries, fallopian tubes, and uterus.

Luteinizing hormone (LH)

A gonadotrophic hormone that causes the ovary to release a mature egg (ovulation). In the male, LH stimulates testosterone production. In the female, LH stimulates progesterone production after ovulation has occurred.


Male factor infertility

When a couple’s infertility is attributed to the man.


Menopause is when your periods stop due to lower hormone levels. This usually happens between the ages of 45 and 55.

Menstrual cycle

The series of changes in hormone levels and structures in the female reproductive system that trigger ovulation and that make pregnancy possible. The length of the menstrual cycle varies, but the average is to have periods every 28 days. Regular cycles that are longer or shorter than this, from 21 to 40 days, are normal.


also known as ‘period’ is the part of the menstrual cycle when a woman bleeds from her vagina for a few days.


Metformin is a drug that can be used by patients with polycystic ovary syndrome (PCOS) who aren’t ovulating properly because of abnormal insulin levels in the body.


The unplanned spontaneous loss of a viable embryo or fetus in the womb. For information and support on miscarriage please see Tommy’s and the NHS.


Mitochondria are present in almost all human cells, including eggs. They create most of a cell’s energy supply which powers every part of our body. For any cell to function, the mitochondrial genes need to work properly. Mitochondria with gene abnormalities can cause severe medical disorders known as mitochondrial disease.

Mitochondrial donation

Mitochondrial donation treatment can be used by people who are at risk of passing on a serious mitochondrial disease to any children they might have. The treatment involves transferring nuclear genetic material (the genes that make you, you) from the mother’s eggs or embryos into the eggs or embryos of a donor with healthy mitochondria. Any children would still be the mother’s and father’s biologically but without the mitochondria that cause the disease.


The ability for an organism to independently. Usually used to describe sperm, which move (swim) on their own.

Multiple birth

The birth of more than one baby from a single pregnancy.



A condition in which the semen only contains dead sperm.

Non-motile sperm

Non-motile sperm are sperm cells that are unable to move.



Also spelt estrogen. This is a female hormone mainly produced by the ovaries from the onset of puberty until menopause. It promotes the growth and maintenance of the female reproductive system.

Ovarian Hyperstimulation Syndrome (OHSS)

OHSS is a reaction to fertility drugs taken to increase egg production. OHSS occurs in women who are very sensitive to the fertility medication resulting in too many eggs developing in the ovaries, which become very large and painful.

Ovarian tissue freezing

Ovarian tissue freezing is a fertility preservation option for patients who are unable to freeze their eggs and for younger people who haven't started ovulating.


The female reproductive organs that produce eggs and oestrogen on a monthly basis under hormonal influence from the pituitary gland.


The release of the egg (ovum) from the ovarian follicle.


Pelvic Inflammatory Disease (PID)

An infection involving the pelvic organs e.g. ovaries and fallopian tubes.


The penis is the male sexual organ. It contains a tube called the urethra, which carries semen from the testicles and urine from the bladder to the outside of the body.

Polycystic Ovary Syndrome (PCOS)

A common condition that affects how the ovaries work.

Pre-implantation genetic testing for aneuploidy (PGT-A)

PGT-A (previously known as preimplantation genetic screening or PGS) is mostly used in cases where patients have had several miscarriages or failed IVF cycles and want to test their embryos for problems which might lead to another failed treatment. It can also be used to check embryos for chromosome problems.

Pre-implantation genetic testing for monogenic disorders (PGT-M)

PGT-M, (previously known as preimplantation genetic diagnosis or PGD), can be used with IVF to check the genes or chromosomes of your embryos for specific genetic conditions such as Cystic Fibrosis and early onset Alzheimer’s. Patients then have the choice of only placing healthy embryos into the womb.

Pre-implantation tissue typing (PTT)

PTT is a type of embryo testing which can be used for families where an existing child has a life-limiting blood disorder and they need a donor that cannot be found from a tissue bank or existing relative.

Posthumous conception

Conceiving with someone's egg, sperm or embryo after they have died.


Qualitative HCG blood test

A blood test to check if there is a hormone called human chorionic gonadotropin (hCG) in your blood which can show up if you are pregnant.


Randomised controlled trial (RCT)

A study in which a number of similar people are randomly assigned to 2 (or more) groups to test a specific drug, treatment or other intervention. One group (the experimental group) has the intervention being tested, the other (the comparison or control group) has an alternative intervention, a dummy intervention (placebo) or no intervention at all. The groups are followed up to see how effective the experimental intervention was. Outcomes are measured at specific times and any difference in response between the groups is assessed statistically. This method is also used to reduce bias.

Reciprocal IVF

This is a way for partners in a female same-sex relationship to both be part of the treatment cycle. Eggs are collected from one partner and fertilised with donor sperm, the resulting embryo is then implanted into the other partner. So, one partner uses her eggs, the other carries the baby and gives birth.

Retrograde Ejaculation

At male orgasm, the seminal fluid containing the sperm goes backwards into the bladder. This is a known complication of diabetes and can affect men with multiple sclerosis.


Secondary infertility

When a patient who has already had a child has difficulty conceiving another.


Semen is the fluid that comes from a penis during ejaculation that contains sperm.

Slow freezing

The process of slowly freezing egg, sperm and embryos to a temperature they can be safely stored.


Sperm cells are male reproductive cells that come from the testicles. They are contained in the semen.

Sperm donation

A donation of sperm with the intention for the sperm to be used in fertility treatments.

Sperm freezing

The process of freezing sperm for use in their own future treatment or to donate to someone else’s treatment.

Sperm washing

A process where sperm cells are separated from the rest of the semen fluid.


Sexually transmitted infections such as Chlamydia also as known as an STD (Sexually transmitted diseases).

Surgical sperm extraction

If you have no, or extremely low numbers of, sperm in your semen which means you can’t have a standard fertility treatment, you may be able to have sperm collected surgically.


The process of a patient carrying a baby on behalf of another person or family.



The testicles, testes or 'balls' are the two, oval male organs which hang below the penis. Sperm and testosterone are produced in the testicles which are the main organs in the male reproductive system.

Testicular tissue freezing

Testicular tissue freezing is a specialist technique to preserve the fertility in people who do not produce viable sperm in their ejaculate (azoospermia) as well as younger people who are unable to produce an ejaculate.


The male sex hormone produced in the testicles.

Transvaginal ultrasound

A scan where the probe is placed inside the vagina.

Treatment add-ons

They are optional additional treatments, also referred to as ‘supplementary’, ‘adjuvants’ or ‘embryology treatments’.

Tubal factor infertility

Tubal factor infertility occurs when the fallopian tubes are blocked due to diseases, damage, scarring, or obstructions that prevent the sperm from reaching and fertilising the egg.


Ultrasound scan

An ultrasound is a method of scanning that uses high frequency sound waves to produce images of internal organs such as the womb and ovaries.

Unexplained infertility

Inability to identify the cause of infertility despite a complete evaluation of semen, ovarian reserve, ovulation, endocrinologic disorders and pelvic anatomy.


See womb.



The canal leading from the vulva to the cervix.


This is a surgical method of sterilisation for men. The tubes carrying the sperm to the penis are cut and sealed to prevent sperm from entering the semen.


A fast-freezing technique which allows eggs, sperm or embryos to be frozen and stored until a patient is ready to use them.


The area surrounding the opening of the vagina. It includes the inner and outer vaginal lips (the labia) and the clitoris.



The womb or uterus is the female reproductive organ in which the embryo develops. At one end, the cervix opens into the vagina, at the other, the fallopian tubes link to the ovaries.


X chromosome

The X chromosome is one of the two sex-determining chromosomes and is found in both males and females.


Y chromosome

The Y chromosome is one of two sex chromosomes. The Y chromosome is normally the sex-determining chromosome in many species, since it is the presence or absence of Y that determines the male or female sex.


Zone pellucida

The shell surrounding the egg/embryo.


A fertilised egg.

Review date: 17 January 2026