Cambridge IVF logo

Mobile menu open

Glossary of terms

We have provided a list of terms to help you understand some of the terminology that is used.



Abstinence involves refraining from any sexual activity, including masturbation.


This is an IVF treatment used to control ovulation. During the agonist cycle, there is an initial surge in hormone production, followed by a reduction, which prevents ovulation


This is an IVF treatment used to control ovulation. During the antagonist cycle, hormone production is suppressed, preventing ovulation.

Assisted conception

Treatments which help people conceive by controlling the way that the sperm and the egg are brought together.



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

Body mass index

The ratio of your weight in kilograms to the square of your height in metres. Your BMI is an indicator of whether your weight is healthy. A healthy weight increases the chance of successful IVF treatment.



A tube that can be inserted into a body cavity, duct or vessel - a catheter may be used either to introduce something into the body, or to drain something from it.


Clinical Commissioning Group


The cervix is the lower portion or 'neck' of the womb which opens into the vagina.


A common sexually transmitted disease (STD), chlamydia can damage a woman's reproductive organs and affect her fertility.

Chromosonal defect

Errors in the number or structure of chromosomes, which are found within human cells can cause abnormalities eg Down's syndrome.


Stands for Cambridge IVF

Clinical pregnancy

A confirmed pregnancy, shown by both high levels of hCG (hormone) in the blood and ultrasound confirmation of a fetal heartbeat.


During compaction, the cells of an embryo bind tightly together into a sphere. This is an important step in the formation of a blastocyst (five/six day old embryo).


The preservation of blastocysts, unfertilised eggs, or sperm, at very low temperatures for use in future treatment cycles.

Culture medium

A liquid or gel designed to support the growth of embryos in the lab.


The IVF treatment cycle describes the complete round of treatment, incorporating all stages of IVF


Data Protection Act

The Data Protection Act (DPA) is the 1998 law designed to protect your personal data, whether this is stored in paper files or on a computer. Your IVF treatment notes, other health records and any other information you choose to share with us, eg by filling in forms on this website, are covered by the DPA.


Diabetes is a long-term condition caused by too much glucose, a type of sugar, in the blood. It happens when the body is not able to produce insulin to control the breakdown of sugar in the blood (Type 1). It may also happen if the body does not produce enough insulin or if the insulin does not work properly (Type 2). Type 2 diabetes is more common and usually occurs in older people. It is linked to obesity in many cases. Diabetes may also occur during pregnancy in women who do not otherwise have the condition. This happens when pregnant women produce so much sugar that their insulin cannot control it.

Donor insemination

Using the sperm of a donor, usually not known to you, to fertilise the eggs during fertility treatment.

Down regulation

"Switching off" the reproductive hormone production before the woman can receive drugs to stimulate egg production during fertility treatment. This describes the antagonist IVF cycle.


Egg collection

The process of collecting eggs from the follicles in your ovaries during IVF treatment.


A fertilised egg where the cells have begun to divide. After five or six days, the embryo becomes a blastocyst.

Embryo transfer

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


Clinical scientist working in the field of fertility. The embryologist is responsible for checking fertility levels, collecting eggs and sperm and processes of bringing them together during fertility treatment. Embryologists are also involved in research, supporting IVF and other fertility treatments.


Condition in which tissue similar to the lining of the womb (endometrium) grows in other parts of the body, most commonly on the ovaries. It can contribute to infertility.


The lining of the womb. This grows and sheds during a normal menstrual cycle. For pregnancy to take place, the blastocyst must implant into the endometrium.


A long tube forming part of the male reproductive system. The epididymis carries the sperm from the testicles. The sperm are then stored in the lower part of the tube until the man comes.


Elective single embryo transfer refers to transferring a one embryo as part of IVF treatment. There are strong arguments, in some cases, for transferring a single embryo (rather than two or three), to prevent multiple pregnancies.


Fallopian tubes

Two long, thin tubes that connect to a woman's ovaries to her womb. The fallopian tubes allow sperm to travel to the eggs after they leave the ovaries and fertilised eggs to move to the womb and implant.


Benign (non-cancerous) tumours that grow in or around the womb. Fibroids can contribute to infertility.

Folic acid

Also known as vitamin B9 [3], vitamin Bc[4] or folacin. Having enough folic acid before you are pregnant and during the early weeks of pregnancy, can significantly reduce the chance of a baby being born with a neural tube defect such as spina bifida.


The follicles are small, fluid-filled sacs in the ovaries in which the eggs develop.

Follicle-Stimulating Hormone

FSH is a hormone which stimulates the production of follicles by the ovaries. It is used during fertility treatment to stimulate the growth of multiple follicles, producing several eggs for use during treatment.

Frozen embryo transfer

The process of transferring embryos into your womb, using embryos which have been frozen after previous IVF treatments. The embryos will have been carefully thawed for use in the current treatment.


GnRH agonists

GnRH is a hormone released by the body which stimulates the production of lutenising hormone and follicle-stimulating hormone. During IVF, GnRH is used to control the fertility cycle. See also 'down regulation' in the jargon buster.


Hormone replacement therapy

HRT is used to replace the female hormones that a woman’s body no longer produces because of the menopause or fertility treatment.

Human Chorionic Gonadatrophin

hCG is a naturally occuring hormone, usually found in the placenta. Artificial hCG is used during IVF to help the eggs mature before they are collected.


An X ray process, showing whether the fallopian tubes are open and womb cavity is a normal shape. During an HSG a special dye is injected into the womb, showing clearly where there are abnormalities. How the dye travels through and out of the fallopian tubes can show up defects and blockages.



This is a surgical examination of the pelvis/abdomen, through a small incision. The surgeon uses a narrow telescopic tool with a small camera attached. This is inserted just below the belly button and allows images to be projected onto a screen. Also sometimes called 'keyhole surgery'.

Lutenising Hormone

A hormone which is essential for the development of eggs and sperm.


Menstrual cycle

This describes the changes which normally take place in a more or less monthly cycle in the ovaries and the lining of the womb. During a normal menstrual cycle, the ovary will release an egg and the womb lining will thicken so that the embryo can implant if the egg is fertilised. If this happens, the cycle ends in pregnancy. If the egg is not fertilised, the thickened lining is shed through the vagina - this is what causes menstruation / periods. See also 'menstruation'.


Menstruation is the formal word for a woman's period. During the normal menstrual cycle, the womb builds up a thick lining. This allows the embryo to implant if the egg released at the start of the menstrual cycle is fertilised. If the egg is not fertilised, the thickened lining is shed through the vagina - this is what causes menstruation / periods.


Loss of a pregnancy in the first 23 weeks.


Size and shape - in the case of fertility treatment this refers to the size and shape of sperm.


The ability to move - in the case of fertility treatment, this refers to the movement of sperm.

Multiple birth

The birth of more than one baby from a single pregnancy, usually twins or triplets.


Natural cycle

A fertility treatment cycle in which no drugs are given to stimulate egg production.



A hormone produced in the ovaries, oestrogen controls sexual development and the reproductive cycle in women.

Ovarian Hyperstimulation Syndrome

OHSS is a potentially serious complication of some treatments, which occurs when the ovaries respond excessively to fertility drugs


Part of the female reproductive system, the two ovaries are attached to the womb by the fallopian tubes. When functioning normally, they produce and release eggs as part of the menstrual cycle. They also produce hormones which are essential for reproduction. Problems with the ovaries may be a cause of fertility problems in women.

Ovary stimulation

The use of drugs to stimulate the ovaries to develop follicles and thus produce more eggs.


Ovulation takes place when an ovary releases one or more eggs. In the normal menstrual cycle, the ovaries alternate in releasing a single egg a month.


'Ovum' is the Latin word for egg. It is used to describe the eggs produced by a woman's ovaries.



The penis is the male sex organ.


A solid, often bullet shaped 'pill' made to be inserted into the vagina or rectum. Pessaries hold drugs which are gradually released as the pessary dissolves at body temperature.

Polyscystic ovaries

Polycystic ovary syndrome is a condition in which small cysts develop aaround the ovaries. This can affect hormone production and hence fertility, as it can result in no ovulation taking place.

Premature menopause

The early onset of menopause, before the age of 40.


One of the female hormones, progesterone is produced after ovulation and encourages the growth of the lining of the womb.


The prostate gland is located just below the bladder. It produces most of the liquid which makes up 20 - 30% of the semen.


Retrograde Ejaculation

Retrograde ejaculation occurs when semen squirts backwards into the bladder instead of out of the penis when a man comes.



Sedatives are drugs which produce a calming effect. You may be given a sedative to relax you before a treatment, rather than having to undergo a general anaesthetic.


Semen is the liquid which emerges from the penis when a man comes. Its purpose is to carry the sperm into and through the vagina, cervix and womb, to the eggs.


A sample collected for testing.


Sperm are reproductive cells produced by men. The word comes from the Greek word for seed. When a man comes, millions of sperm cells are carried into the woman's reproductive system in the semen.

Sperm Preparation Test

The method by which sperm are separated from seminal liquid so that they can be used for IVF.



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.


Testosterone is the main male sex hormone and is necessary for normal sperm development.

Transvaginal Ultrasound

Transvaginal ultrasound is a type of ultrasound scan of eg the womb and its lining and/or the ovaries. During this scan a wand-like probe is placed into the vagina, enabling the clinician to get a good view of the pelvic organs.

Tubal blockage

If the fallopian tubes are blocked, this can cause infertility as the sperm cannot reach the eggs. The eggs also cannot travel from the ovaries to the womb. Tubal blockage may be caused by disease eg pelvic infection or endometriosis. It can also be used intentionally during sterilisation.



Ultrasound is a method of scanning which uses high frequency sound waves to produce images of internal organs, eg the womb and ovaries.


The uterus or womb 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.



The vagina is the tube leading from the womb to the outside of the body.

Vas Deferens

The vas deferens is a pair of tubes which carry the sperm into the penis.


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.


Zona Pellucida

A clear membrane which surrounds the egg and the developing embryo for the first few days after fertilisation. After five days the blastocyst 'hatches' through the zona.


The zygote is the initial cell which forms when the sperm fertilises the egg.