Glossary
Find below some common terms and acronymns used in IVF
Common IVF terms
A
Anti-Müllerian Hormone (AMH)
A hormone produced by small follicles in the ovaries. An AMH blood test is commonly used as an indicator of ovarian reserve, although it cannot tell you the quality of your eggs or whether you will become pregnant.
Antral Follicle Count (AFC)
The number of small follicles visible in the ovaries during an ultrasound scan. AFC is one of the tests used to assess ovarian reserve and can help doctors estimate how the ovaries may respond to IVF medication.
Assisted Hatching
A laboratory technique in which a small opening is made in the outer layer of an embryo (the zona pellucida). It has been proposed that this may help an embryo hatch before implantation, although its benefit is not established for everyone.
Assisted Reproductive Technology (ART)
A general term for fertility treatments in which eggs or embryos are handled outside the body. IVF and ICSI are examples of ART.
B
Baseline Scan
An ultrasound scan, usually performed at the beginning of an IVF cycle, to check the ovaries and uterus before stimulation medication is started.
A blood test that measures human chorionic gonadotropin (hCG), the hormone produced after implantation. It is commonly used to confirm pregnancy following IVF.
Beta hCG
(β-hCG)
Blastocyst
An embryo that has developed for approximately five to seven days after fertilisation and contains a larger number of cells. Blastocysts are commonly used for embryo transfer and embryo biopsy.
Blastocyst Grading
When one or both fallopian tubes are blocked, preventing sperm and egg from meeting naturally. IVF can bypass the fallopian tubes.
Blocked Fallopian Tubes
A system used by embryologists to assess the appearance and development of a blastocyst. It usually considers the inner cell mass, trophectoderm and degree of expansion.
C
Carrier Screening
Genetic testing used to determine whether a person carries a genetic variant associated with an inherited condition. A carrier may have no symptoms but could potentially pass the condition to a child.
Chemical Pregnancy
A very early pregnancy in which hCG is detected but the pregnancy does not continue to develop. It may occur before anything can be seen on an ultrasound scan.
Chromosome Abnormality
A change in the number or structure of chromosomes. Some chromosomal abnormalities can affect embryo development, implantation or pregnancy.
Cleavage-Stage Embryo
Clomiphene
A medication that can stimulate ovulation. It may be used in some fertility treatments but is less commonly used in conventional IVF than injectable stimulation medications.
Corpus Luteum
A temporary structure that develops in the ovary after ovulation. It produces hormones, particularly progesterone, which supports the uterine lining in early pregnancy.
D
Donor Egg
IVF
IVF treatment using eggs donated by another woman. The donor eggs are fertilised with sperm and the resulting embryos may be transferred to the intended mother or another person carrying the pregnancy.
Donor
Sperm
Sperm provided by a sperm donor for use in fertility treatment.
Donor Embryo
An embryo created using donated eggs and sperm and donated to another person or couple for fertility treatment.
Down Regulation
Medication used in some IVF protocols to temporarily suppress the natural reproductive hormone cycle. This allows the timing of ovarian stimulation and egg collection to be controlled.
E
Egg Collection
A procedure used to remove mature eggs from the ovaries following ovarian stimulation. It is usually performed using a needle guided through the vagina by ultrasound.
Egg
Freezing
The process of collecting and freezing unfertilised eggs for potential future use.
Egg
Retrieval
Another term for egg collection.
Embryo
The stage of development following fertilisation of an egg by sperm. During IVF, embryos are developed in the laboratory before transfer or freezing.
Embryo Biopsy
A procedure in which a small number of cells are removed from an embryo, usually at the blastocyst stage, for genetic testing.
Embryo Grading
The process of assessing an embryo’s appearance and development under a microscope. Grading can help embryologists select embryos for transfer or freezing, but appearance alone cannot determine whether an embryo will result in a healthy pregnancy.
Embryo Transfer
The procedure in which an embryo is placed into the uterus using a thin catheter.
Endometrium
The lining of the uterus. An embryo implants into the endometrium
Endometriosis
A condition in which tissue similar to the lining of the uterus grows outside the uterus. It can sometimes affect fertility.
ERA – Endometrial Receptivity Analysis
A test intended to assess the timing of endometrial receptivity and identify a proposed personalised window for embryo transfer. Its usefulness in routine IVF treatment remains debated.
Euploid Embryo
An embryo with the expected number of chromosomes based on the genetic test performed. A euploid result does not guarantee implantation or a healthy baby.
F
Fertilisation
The process in which a sperm and egg combine to form an embryo.
Frozen Embryo Transfer
An embryo transfer using an embryo that was previously frozen and subsequently thawed.
Follicle
A fluid-filled structure in the ovary that contains an immature egg. During IVF stimulation, multiple follicles are encouraged to develop.
Follicle Stimulating Hormone
A hormone involved in the development of ovarian follicles. FSH is also used as a medication during many IVF cycles to stimulate the ovaries.
G
Gestational Carrier
A person who carries a pregnancy for another individual or couple. The gestational carrier does not provide the egg used to create the embryo.
Genetic Counselling
A consultation with a genetics professional to discuss genetic conditions, genetic testing, test results and potential reproductive implications.
Genetic Testing of Embryos
Testing performed on cells taken from an embryo to look for particular genetic or chromosomal conditions.
H
Hatching
The process by which an embryo breaks through its outer layer, the zona pellucida, before implantation.
Human Chorionic Gonadotropin
A hormone produced after implantation. hCG is the hormone detected by pregnancy tests.
Hysteroscopy
A procedure in which a small camera is inserted through the cervix to examine the inside of the uterus. It may be used to investigate or treat certain uterine abnormalities.
I
ICSI – Intracytoplasmic Sperm Injection
A laboratory procedure in which a single sperm is injected directly into an egg to assist fertilisation.
Implantation
The process in which an embryo attaches to and begins to grow within the lining of the uterus.
Implantation Failure
When an embryo transfer does not result in implantation or an ongoing pregnancy. Repeated implantation failure can have many possible causes.
Infertility
The inability to achieve pregnancy after a period of regular unprotected intercourse, or a situation in which medical assistance is required to achieve pregnancy.
Insemination
The introduction of sperm into the reproductive tract. Intrauterine insemination (IUI) places prepared sperm directly into the uterus.
IUI – Intrauterine Insemination
A fertility treatment in which prepared sperm is placed directly into the uterus around the time of ovulation.
IVF – In Vitro Fertilisation
A fertility treatment in which eggs are collected from the ovaries and fertilised with sperm in a laboratory. Resulting embryos can then be transferred to the uterus or frozen for future use.
L
Luteal Phase
The part of the menstrual cycle after ovulation and before the next period. Progesterone is an important hormone during this phase
Luteal Support
Medication, usually progesterone, given after egg collection or embryo transfer to support the uterine lining.
M
Mature Egg
An egg that has reached the appropriate stage of development to be fertilised. Mature eggs are generally identified as MII eggs during IVF.
MII Egg
An egg that has reached metaphase II, the mature stage at which it can normally be fertilised.
Mosaic Embryo
An embryo in which testing identifies a mixture of cells with different chromosome results. The significance of a mosaic result can depend on the type and level of mosaicism and should be discussed with a fertility specialist and genetic counsellor.
Mitochondria
Structures within cells that produce energy. Mitochondria contain their own small amount of DNA, known as mitochondrial DNA.
Mitochondrial DNA (mtDNA)
DNA contained within mitochondria rather than the cell nucleus. Mitochondrial DNA is inherited through the maternal line.
Mitochondrial Replacement Therapy (MRT)
A reproductive technique designed to prevent transmission of serious mitochondrial disease by creating an embryo containing nuclear DNA from the intended parents and mitochondria from a donor. The technique is highly specialised and is subject to specific legal and regulatory requirements.
N
Natural Killer
(NK) Cells
A type of immune cell. NK-cell testing and treatments have been proposed in some fertility settings, but their role in implantation and recurrent pregnancy loss remains an area of ongoing research and debate.
Natural
Cycle FET
A frozen embryo transfer cycle that follows the person’s natural menstrual cycle and ovulation rather than using medication to prepare the uterine lining.
NIPT – Non-Invasive Prenatal Testing
A blood test performed during pregnancy that analyses fragments of placental DNA in the mother’s bloodstream to screen for certain chromosomal conditions. It is a screening test rather than a definitive diagnosis.
O
OHSS – Ovarian Hyperstimulation Syndrome
A complication that can occur when the ovaries respond strongly to fertility medication. Symptoms can range from mild bloating and discomfort to, rarely, a serious condition requiring medical treatment.
Oocyte
The medical term for an egg cell.
Oocyte Retrieval
Another term for egg collection.
Ovarian Reserve
An estimate of the number of eggs remaining in the ovaries. AMH and antral follicle count are commonly used to assess ovarian reserve.
Ovarian Stimulation
The use of fertility medication to encourage the ovaries to develop multiple follicles during an IVF cycle.
Ovulation
The release of an egg from an ovary.
P
PGT-A – Preimplantation Genetic Testing
A test used to assess whether an embryo has an abnormal number of chromosomes. It was previously commonly called PGS.
PGT-M – Preimplantation Genetic Testing for Monogenic Conditions
Testing used to identify specific inherited genetic conditions caused by changes in a single gene.
PGT-SR – Preimplantation Genetic Testing for Structural Rearrangements
Testing used when one of the intended parents carries a structural chromosome rearrangement, such as a translocation.
Progesterone
A hormone that helps prepare and maintain the uterine lining for implantation and early pregnancy.
Pronuclei
Structures containing the genetic material from the egg and sperm shortly after fertilisation and before their genetic material combines.
R
Recurrent Implantation Failure
A term sometimes used when multiple embryo transfers have failed to result in an ongoing pregnancy. There is no universally agreed definition, and possible causes can be complex.
Recurrent Pregnancy Loss
Repeated pregnancy losses. The definition varies between clinical guidelines and countries, and investigation may be recommended depending on an individual’s circumstances
Retrieval
Short for egg retrieval or egg collection - the procedure used to collect eggs from the ovaries.
S
Semen
Analysis
A test assessing sperm, commonly including concentration, motility and morphology.
Sperm Concentration
The number of sperm present in a given volume of semen.
Sperm Motility
The percentage of sperm that are moving. Motility is one of the measurements used to assess sperm quality.
Sperm Morphology
The assessment of the size and shape of sperm. Abnormal morphology does not necessarily mean that natural conception or IVF is impossible.
Stimulation
The stage of an IVF cycle during which medication is used to encourage multiple follicles to develop.
Subfertility
A term sometimes used when conception is taking longer than expected but pregnancy remains possible.
T
Trigger
Injection
Medication given towards the end of ovarian stimulation to help finalise egg maturation and prepare for egg collection. Egg collection is usually scheduled approximately 34–36 hours afterwards, depending on the protocol.
Trophectoderm
The outer layer of cells in a blastocyst. These cells eventually contribute to the placenta. Trophectoderm cells are typically the cells sampled during embryo biopsy for PGT.
U
Ultrasound
Scan
An imaging procedure using sound waves to view the reproductive organs. Ultrasound is routinely used during IVF to monitor follicles and the uterine lining.
Uterine
Lining
Another term for the endometrium - the lining of the uterus into which an embryo may implant.
V
Vitrification
A rapid freezing technique used to preserve eggs and embryos. It has largely replaced older slow-freezing techniques in modern IVF laboratories.
W
Withdrawal
Bleed
Bleeding that occurs after stopping certain hormone medications. It can resemble a period but is not necessarily the result of natural ovulation.
Window of Implantation
A proposed period during which the endometrium is receptive to embryo implantation. The exact timing and usefulness of tests designed to identify an individual window remain areas of research.
Z
Zona
Pellucida
The protective outer layer surrounding an egg and early embryo. The embryo must eventually hatch through this layer before implantation.
Common IVF Abbreviations
AFC – Antral Follicle Count
AMH – Anti-Müllerian Hormone
ART – Assisted Reproductive Technology
β-hCG – Beta Human Chorionic Gonadotropin
DNA – Deoxyribonucleic Acid
ESHRE – European Society of Human Reproduction and Embryology
FET – Frozen Embryo Transfer
FSH – Follicle-Stimulating Hormone
HCG/hCG – Human Chorionic Gonadotropin
ICSI – Intracytoplasmic Sperm Injection
IUI – Intrauterine Insemination
IVF – In Vitro Fertilisation
MRT – Mitochondrial Replacement Therapy
mtDNA – Mitochondrial DNA
NIPT – Non-Invasive Prenatal Testing
OHSS – Ovarian Hyperstimulation Syndrome
PGT – Preimplantation Genetic Testing
PGT-A – Preimplantation Genetic Testing for Aneuploidy
PGT-M – Preimplantation Genetic Testing for Monogenic Conditions
PGT-SR – Preimplantation Genetic Testing for Structural Rearrangements
SART – Society for Assisted Reproductive Technology
WHO – World Health Organization