Terminology and Glossary

Surrogacy or Surrogate means substitute. In medical parlance, the term surrogacy means using of a substitute mother in the place of the natural mother.

A surrogacy arrangement is one in which one woman (the surrogate mother) agrees to bear a child for a couple (the intended parents) and surrender it at birth. This provides an opportunity for those who are unable to carry a child themselves to overcome their childlessness.

The surrogate becomes pregnant via embryo transfer with a child of which she is not the biological mother. She may have made an arrangement to relinquish it to the biological mother or father to raise, or to a parent who is unrelated to the child (e. g. because the child was conceived using egg donation, sperm donation or is the result of a donated embryo). The surrogate mother may be called the gestational surrogacy carrier.

Altruistic surrogacy is a situation where the surrogate receives no financial reward for her pregnancy or the relinquishment of the child (although usually all expenses related to the pregnancy and birth by surrogacy are paid by the intended parents such as medical expenses, maternity clothing, and other related expenses).

Commercial surrogacy is a form of surrogacy in which a gestational carrier is paid to carry a child to maturity in her womb and is usually resorted to by higher income infertile couples who can afford the cost involved or people who save and borrow in order to complete their dream of being parents. This procedure is legal in several countries including in India where due to high international demand and ready availability of poor surrogacy it is reaching industry proportions. Commercial surrogacy is sometimes referred to by the emotionally charged and potentially offensive terms “wombs for rent”, “outsourced pregnancies” or “baby farms”.


Term UsedExplanation
Abandoned CycleIn IVF, where a treatment cycle is cancelled after commencing administration of drugs but before embryo transfer.
Adjusted Live Birth RateThe 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 hatchingThe mechanical, chemical or laser breaching of the gelatinous coating of the eggs.
AutosomalPertaining to any chromosome that occurs in the nucleus, except for the sex chromosomes.
Autosomal Dominant DisordersDisorders 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 DisordersDisorders, 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 MucusThe secretions surrounding the cervical canal. The amount and texture change during ovulation to allow sperm penetration.
Chromosomea thread-like structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
Clinical Pregnancya pregnancy that is confirmed by both high levels of hCG (the pregnancy hormone) and ultrasound confirmation of a gestational sac or heartbeat (fetal pole).
Clinical Pregnancy RateThis is calculated as a proportion of pregnancies with beating heart for every 100 treatment cycles commenced.
CloningThe production of genetically identical (sharing the same nuclear gene set) individuals.
ClonesOrganisms that are genetically identical (share the same nuclear gene set) to each other
CongenitalMalformations, 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 AbnormalitiesDeformities or diseases which are either present at birth or show themselves soon after birth.
ConsentAcceptance 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.
CounsellingAll 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.
CryopreservationThe freezing of oocytes, spermatozoa or embryos and their storage in liquid nitrogen.
Cystic FibrosisA 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.
CytoplasmThe material between the nucleus and the cell surface
DirectionsThe 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.
DonorThe 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.
Drugswhich may be used in IVF treatment
Buserelinis 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.
HCG– 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
HMGHuman Menopausal Gonadotrophin (may be called Pergonal or Humegon) stimulates the development of egg follicles.
FSHFollicle Stimulating Hormone (may be called Metrodin) can be given also to stimulate egg follicles.
Egg CollectionProcedure 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.
EmbryoA fertilised egg up to eight weeks of development. At two weeks it is approximately 1-1.5mm in diameter.
EmbryologistA scientist who creates, cultures and studies embryos in a clinical or research laboratory.
Embryo BiopsyRemoval and examination of one or more cells from a developing embryo for diagnostic purposes.
Embryo FreezingEmbryos not required for treatment in a cycle can be frozen and stored for future use. Freezing is also known as cryopreservation.
Embryo StorageThe storage of one or more frozen embryos for future use.
Embryo TransferTransfer of one or more embryos to the uterus
EndometriosisA 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
EpididymisCoiled 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 FactorThis term covers any reason why a woman is infertile, such as ovulation failure or damage to the fallopian tubes.
FoetusThe term used for an embryo after the eighth week of development until birth.
Follicle(s)A small sac in the ovary in which the egg develops.
GameteThe 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 CounsellingA 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 TestingTesting to detect the presence or absence of, or change in, a particular gene or chromosome
GonadotrophinsDrugs 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.
HepatitisRefers to infection with one of the hepatitis viruses which causes acute or chronic inflammation of the liver cells.
HFEAHuman Fertilisation and Embryology Authority
HormoneHormones 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 InseminationInsemination 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.
LaparoscopyThis 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 DisorderDisorders that normally become symptomatic in adult life.
Live BirthThe delivery of one or more babies.
Live Birth RateThe number of live births achieved from every 100 treatment cycles commenced.
Male FactorThis 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 CycleA 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.
MicromanipulationThis 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
MiscarriageSpontaneous complete loss of a pregnancy before 24 weeks.
Monogenic Disorders– Disorders arising from defects in a single gene.
Multiple BirthBirth of more than one baby from a pregnancy (these are counted as single live births irrespective of the number of babies born).
Multiple Birth RateThis is the percentage of all births in which more than one baby was born.
Multiple PregnancyA pregnancy in which two or more foetal hearts are present
Multiple Pregnancy RateThis rate is calculated as a proportion of all clinical pregnancy
Muscular DystrophyA hereditary condition where muscles slowly waste away
MutationThe change in a gene or chromosome that causes a disorder or the inherited susceptibility to a disorder.
Natural/Unstimulated cycleNo drugs were given to stimulate egg production
Neonatal DeathThe death of a baby within 27 complete days of delivery.
OocyteAnother name for an egg
OvaryOne 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 DeathThe death of a baby either in the uterus after 24 weeks pregnancy (stillbirth) or within 28 days after the birth.
Polygenic or multifactorial conditionsThe interaction of several genes and the environment
Pregnancy RateThe 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 StreakThis develops in an embryo by day 14 when the cells which form the foetus separate from those which form the placenta and umbilical cord.
RecipientThe woman who receives eggs from another woman during treatment to help her to become pregnant.
SpermatidAn immature sperm cell.
StillbirthThe birth of a dead infant
Stimulated CycleA treatment cycle in which stimulation drugs are used to produce more eggs than usual in the woman’s monthly cycle.
Stimulation DrugsDrugs 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.
Superovulation/StimulationThe stimulation of a woman’s ovaries with drugs to produce more eggs than usual in a monthly cycle.
Superovulatory Drugshormones 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.
TestisTesticle or male gonad
Transport (or Satellite) IVFAn 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 disorderscaused 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.
Ultrasoundinvestigation 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 OutcomeThe outcome of a clinical pregnancy is unknown due to incomplete information being returned by a clinic to the HFEA.
UnstimulatedNo drugs were given to stimulate egg production.
X-Linked DisordersDisorders 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.