IVF Glossary


Term Used


Abandoned Cycle

In IVF, where a treatment cycle is cancelled after commencing administration of drugs but before embryo transfer.

Adjusted Live Birth Rate

The live birth rate (number of births rate for every 100 treatment cycles) once it has been adjusted to take account of the different types of patients which the clinic treated during the year.

Assisted hatching

The mechanical, chemical or laser breaching of the gelatinous coating of the eggs.


Pertaining to any chromosome that occurs in the nucleus, except for the sex chromosomes.

Autosomal Dominant Disorders

Disorders where inheritance of a mutation from one parent only (or arising anew during egg or sperm formation) can be sufficient for the person to be affected. Important dominant disorders in the UK include familial hypercholesterolaemia, Huntington's Disease, adult polycystic kidney disease and familial adenomatous polyposis coli (colon cancer).

Autosomal Recessive Disorders

Disorders, where for a person to be affected, a mutation has to be inherited from both parents. Such parents are usually unaffected carriers because they only have a single copy of the mutant gene. Recessive disorders commonly have onset in childhood and include cystic fibrosis, sickle cell disease and thalassaemia.

Cervical Mucus

The secretions surrounding the cervical canal. The amount and texture change during ovulation to allow sperm penetration.


Small bodies within the nucleus of every cell in the body. They contain the genes.

Clinical Pregnancy

Small bodies within the nucleus of every cell in the body. They contain the genes

Clinical Pregnancy Rate

This is calculated as a proportion of pregnancies with beating heart for every 100 treatment cycles commenced.


The production of genetically identical (sharing the same nuclear gene set) individuals.


Organisms that are genetically identical (share the same nuclear gene set) to each other


Malformations, deformities, diseases etc. are those which are either present at birth, or which, being transmitted direct from the parents, show themselves soon after birth.

Congenital Abnormalities

Deformities or diseases which are either present at birth or show themselves soon after birth.


Acceptance of the procedures involved in donation. A donor must give consent before any of the procedures begin. Before she gives consent, a clinic must have given her adequate information and offered counselling. Consent is given by completing and signing a form supplied by the HFEA to the clinic. This consent to the use and storage of eggs and embryos made from those eggs is called 'informed consent'. Consent to a medical procedure, such as egg collection is called 'valid consent'. Consent can be changed - it may be withdrawn or varied at any time unless the embryo concerned has already been used.


All licensed clinics are required to offer patients counselling. Such counselling aims to enable the patient to understand the implications of treatment, to give emotional support and to help the patient cope with the consequences of treatment.


The freezing of oocytes, spermatozoa or embryos and their storage in liquid nitrogen.

Cystic Fibrosis

A disorder of the mucus-secreting glands of the lungs, the pancreas, the mouth, and the gastro-intestinal tract. The commonest serious genetic disease in Caucasian children.


The material between the nucleus and the cell surface


The HFE Act allows the HFEA to impose additional conditions on licensed activities. These Directions cover areas where primary legislation would be inappropriate because of the need for flexibility. Directions can be applied to an individual clinic or generally.


The woman who gives eggs to help another woman become pregnant or for use in research.

Donor Insemination (DI)

The insemination of donor sperm into (DI) the vagina, the cervix or the womb itself.


Which may be used in IVF treatment


Is a hormone suppressant which is given by nasal spray or a daily injection. Buserelin suppresses the activity of a small gland in the brain called the pituitary gland which normally stimulates the ovaries to produce eggs. The ovaries can then be stimulated artificially.


Human Chorionic Gonadotrophin (may be called Gonadotraphon LH, Pregnyl or Profasi) is given by injection about 34-36 hours before egg collection. It helps to ripen the eggs within the follicles


Human Menopausal Gonadotrophin (may be called Pergonal or Humegon) stimulates the development of egg follicles.


Follicle Stimulating Hormone (may be called Metrodin) can be given also to stimulate egg follicles.

Egg Collection

Procedure by which eggs are collected from the woman's ovaries by using an ultrasound guided needle or by using a laparoscope (an instrument for looking into the abdomen) and a needle. Also known as egg retrieval.


A fertilised egg up to eight weeks of development. At two weeks it is approximately 1-1.5mm in diameter.


A scientist who creates, cultures and studies embryos in a clinical or research laboratory.

Embryo Biopsy

Removal and examination of one or more cells from a developing embryo for diagnostic purposes.

Embryo Freezing

Embryos not required for treatment in a cycle can be frozen and stored for future use. Freezing is also known as cryopreservation.

Embryo Storage

The storage of one or more frozen embryos for future use.

Embryo Transfer

Transfer of one or more embryos to the uterus


A female condition in which endometrial cells, which normally line the uterus, implant around the outside of the uterus and/or ovaries, causing internal bleeding, pain and reduced fertility


Coiled tubing outside the testicles which store sperm.

Fallopian Tube(s)

The tubes between the ovaries and the uterus. After release of the egg from one of the ovaries, the tube transports the egg to the uterus

Female Factor

This term covers any reason why a woman is infertile, such as ovulation failure or damage to the fallopian tubes.


The term used for an embryo after the eighth week of development until birth.


A small sac in the ovary in which the egg develops.


The male sperm or the female egg.

Gamete Intra Fallopian Transfer (GIFT)

A procedure in which eggs are retrieved from the woman, mixed with sperm and immediately replaced in one or other of the woman's fallopian tubes so that they fertilise inside the body.

Genetic Counselling

A process by which information is imparted to those affected by, or at risk of a genetic disorder. It includes information on the nature of the disorder, the size and extent of genetic risks, the options, including genetic testing, that may help clarify the risks, and the available preventative, supportive and therapeutic measures. In the context of genetic testing it may include responding to the concerns of individuals referred and their families, discussing the consequences of a test, and help to choose the optimal decision for themselves, but not determining a particular course of action.

Genetic Testing

Testing to detect the presence or absence of, or change in, a particular gene or chromosome


Drugs used to stimulate the ovaries similar in composition to natural follicle stimulating hormone (FSH) produced by the pituitary gland.

Hamster Test (HEPT)

A test of the fertilising ability of human sperm by observing their penetration into the hamster egg.


Refers to infection with one of the hepatitis viruses which causes acute or chronic inflammation of the liver cells.


Human Fertilisation and Embryology Authority


Hormones are natural chemical substances produced by the body some of which control the development and release of the egg from the ovary during each menstrual cycle. Natural and synthetic preparations of those hormones are used to increase the number of eggs produced in a cycle.

Intra Cytoplasmic Sperm Injection (ICSI)

A micromanipulation technique. A variation of IVF treatment where a single sperm is injected into the inner cellular structure of the egg. This technique is used for couples in which the male partner has severely impaired or few sperm.

Intrauterine Insemination

Insemination of sperm into the uterus of a woman.

In Vitro Fertilisation (IVF)

Eggs and sperm are collected and put together to achieve fertilisation outside the body. Up to three of the resulting embryos can be transferred into the woman's womb and a pregnancy may occur.


This is a surgical procedure for looking inside the pelvic cavity. Usually under a general anaesthetic, a small cut is made below the navel and a fine optical instrument is inserted. Laparoscopy is used in egg collection.

Late Onset Disorder

Disorders that normally become symptomatic in adult life.

Live Birth

The delivery of one or more babies.

Live Birth Rate

The number of live births achieved from every 100 treatment cycles commenced.

Male Factor

This term covers any reason why the male partner's sperm may be less effective or incapable of fertilisation, including the absence of viable sperm and a failed reversal of a vasectomy.

Menstrual Cycle

A cycle of approximately one month in the female during which the egg is released from an ovary, the uterus is prepared to receive the fertilised egg and blood and tissue are lost via the vagina if a pregnancy does not occur.


This term covers any technique used in IVF to bypass the zona pellucida (protein shell) which surrounds the egg, as this frequently prevents sperm which have poor motility or morphology from penetrating and fertilising the egg. ICSI is the most commonly used method of micromanipulation.

Microsurgical Epididymal Sperm Aspiration (MESA)

Retrieving sperm directly from the epididy


Spontaneous complete loss of a pregnancy before 24 weeks.

Monogenic Disorders

Disorders arising from defects in a single gene.

Multiple Birth

Birth of more than one baby from a pregnancy (these are counted as single live births irrespective of the number of babies born).

Multiple Birth Rate

This is the percentage of all births in which more than one baby was born.

Multiple Pregnancy

A pregnancy in which two or more foetal hearts are present

Multiple Pregnancy Rate

This rate is calculated as a proportion of all clinical pregnancy

Muscular Dystrophy

A hereditary condition where muscles slowly waste away


The change in a gene or chromosome that causes a disorder or the inherited susceptibility to a disorder.

Natural/Unstimulated cycle

No drugs were given to stimulate egg production

Neonatal Death

The death of a baby within 27 complete days of delivery.


Another name for an egg


One of a pair of female reproductive organs which produce eggs and hormones.

OvarianHyperstimulation Syndrome (OHSS)

A rare but serious consequence of taking the drugs used to stimulate the ovaries.

Partial Zonal Dissection (PZD)

A variation of IVF treatment in which a small hole is made in the outer membrane of the egg using a small glass needle, thereby easing the passage of sperm into the egg under their own motion.

Percutaneous Epididymal Sperm Aspiration (PESA)

Retrieving sperm directly from the coiled tubing outside the testicles that store sperm (epididymis) using a needle.

Perinatal Death

The death of a baby either in the uterus after 24 weeks pregnancy (stillbirth) or within 28 days after the birth.

Polygenic or multifactorial conditions

The interaction of several genes and the environment

Pregnancy Rate

The number of pregnancies achieved from every 100 treatment cycles commenced.

Preimplantation Genetic Diagnosis (PGD)

Use of genetic testing on a live embryo to determine the presence, absence or change in a particular gene or chromosome prior to implantation of the embryo in the uterus of a woman.

Prenatal Diagnosis (PND)

Amniocentesis - This method involves examining fetal cells taken between 15 and 16 weeks of pregnancy from the amniotic fluid which surrounds the fetus. The fetal cells are cultured and the genetic make-up of the fetus determined. This allows testing for chromosomal abnormalities such as Down's syndrome and other birth defects. 
Chorionic Villus Sampling (CVS) - This method involves the removal of a small sample of placental tissue between 9 and 11 weeks of pregnancy which is tested for genetic abnormalities.

Primitive Streak

This develops in an embryo by day 14 when the cells which form the foetus separate from those which form the placenta and umbilical cord.


The woman who receives eggs from another woman during treatment to help her to become pregnant.


An immature sperm cell.


The birth of a dead infant

Stimulated Cycle

A treatment cycle in which stimulation drugs are used to produce more eggs than usual in the woman's monthly cycle.

Stimulation Drugs

Drugs used to stimulate a woman's ovaries to produce more eggs than usual in a monthly cycle; also known as superovulatory drugs.

Sub Zonal Insemination (SUZI)

A variation of IVF treatment where a single sperm is deposited into the perivitelline space between the egg and its protein shell (the zona pellucida). This technique is aimed at patients who have sperm which fail to penetrate the zona.


The stimulation of a woman's ovaries with drugs to produce more eggs than usual in a monthly cycle.

Superovulatory Drugs

Hormones given to a woman so that she produces more eggs than usual in a monthly cycle. The drugs contain human menopausal gonadotrophin

Testicular Sperm Extraction (TESE)

Retrieving sperm directly from the testis.


Testicle or male gonad

Transport (or Satellite) IVF

An arrangement whereby IVF is carried out at a primary centre (HFEA licensed) but other parts of the treatment (e.g. ovulation induction or egg retrieval) are performed at a secondary centre (not necessarily HFEA licensed). The embryology and embryo transfer take place at the primary centre.

Treatment Cycle

IVF with fresh embryos: a cycle begins with the administration of drugs for the purpose of superovulation or, if no drugs are used, with the attempt to collect eggs;
IVF with frozen-thawed embryos: a cycle begins with the removal of the stored embryo in order to be thawed and then transferred;
DI: a cycle begins when the first insemination with donor sperm takes place.

Triplet or trinucleatide repeat disorders

Caused by the expansion of a triplet repeat of bases within a gene and are usually associated with neurological disorders e.g fragile X, Huntington disease, myotonic dystrophy. Each disease has a range of repeats associated with a spectrum from normal to affected individuals.


Investigation using sound waves to make a picture of the womb and ovaries appear on a television screen. Ultrasound is used in monitoring egg development and in egg collection.

Unknown Outcome

The outcome of a clinical pregnancy is unknown due to incomplete information being returned by a clinic to the HFEA.


No drugs were given to stimulate egg production.

X-Linked Disorders

Disorders due to a mutation on the X chromosome. X-linked disorders usually only affect males, but the disorders can be transmitted through healthy female carriers.

Zona drilling (ZD)

Acid released to dissolve the gelatinous coating of the egg leaving a hole through which the sperm can enter.