IVF and Fertility Glossary: The Terms You Will Actually Hear

IVF has a vocabulary of its own, and most people meet it in fragments: a word on a pathology form, an abbreviation in a text message from the nurse, a number read out over the phone. This page collects the terms in one place and groups them by where in the process you are likely to encounter them, rather than alphabetically, so that related words sit together.

Hormones and blood tests

• AMH (anti-Müllerian hormone) – a hormone produced by small developing follicles in the ovaries, measured on a blood test. It is used as a marker of ovarian reserve, meaning the size of the remaining pool of eggs, and it helps predict how many eggs a stimulation cycle is likely to produce. It does not measure egg quality and it is not a test of whether you can conceive naturally. Results are reported in different units by different laboratories, so a figure only means something against the reference range of the lab that ran it.
• Antral follicle count (AFC) – a count of the small resting follicles visible on both ovaries during a transvaginal ultrasound, usually early in the menstrual cycle. Like AMH, it is a marker of ovarian reserve and a predictor of response to stimulation. It is operator-dependent, so counts can vary between scans and between sonographers.
• FSH (follicle stimulating hormone) – a hormone released by the pituitary gland that stimulates follicles in the ovary to grow. It is measured on a blood test, conventionally early in the cycle, and a synthetic form of it is the main drug used in ovarian stimulation. In men, FSH acts on the testes and contributes to sperm production.
• LH (luteinising hormone) – a pituitary hormone that rises sharply mid-cycle and triggers ovulation. In IVF, LH is monitored because a premature natural surge can release eggs before they can be collected, which is the problem that agonist and antagonist drugs are designed to prevent.
• Oestradiol – the main form of oestrogen produced by growing follicles. Blood oestradiol is measured repeatedly during stimulation because it rises as follicles develop, giving the clinic an indication of how the ovaries are responding alongside the ultrasound picture.
• Progesterone – the hormone produced after ovulation by the corpus luteum, the structure left behind by a released follicle. It prepares and maintains the uterine lining for implantation. Progesterone is measured to confirm ovulation, monitored around trigger and transfer, and given as medication in most IVF cycles.
• hCG (human chorionic gonadotrophin) – the hormone produced by a developing pregnancy, and the hormone detected by a pregnancy test. Because hCG behaves in the body much like LH, a synthetic form is also used as the trigger injection to bring eggs to final maturity before collection.

One thing worth knowing about all of the above: laboratories use different assays and report against different reference ranges, and a value that is flagged as unusual by one lab may be unremarkable at another. A single hormone result also means much less on its own than it does alongside your age, your scan findings and your history. Ask your clinic to interpret your numbers against their own reference range rather than comparing them with figures found online.

Stimulation and monitoring

• Ovarian stimulation – the phase of an IVF cycle in which daily injections of follicle stimulating hormone are used to encourage a number of follicles to grow together, rather than the single follicle of a natural cycle. It typically runs for somewhere between one and two weeks, with the exact length decided by how your follicles respond.
• Downregulation – the deliberate temporary suppression of your own pituitary hormones before or during stimulation, so that the cycle is controlled by the medication rather than by your natural cycle. It is achieved with a GnRH agonist, and it is why some protocols involve a period of nasal spray or injections before stimulation begins.
• Agonist (GnRH agonist) – a class of drug that first stimulates and then, with continued use, suppresses the pituitary release of FSH and LH. Used in what are commonly called long or agonist protocols, and also used in some cycles as the trigger injection.
• Antagonist (GnRH antagonist) – a class of drug that blocks the pituitary receptor directly and suppresses LH immediately, without the initial stimulating effect. It is usually started partway through stimulation, once follicles reach a certain size, and it gives what are commonly called short or antagonist protocols.
• Follicle tracking – the series of transvaginal ultrasound scans and blood tests through the stimulation phase that let the clinic measure how many follicles are growing, how large they are and what your hormone levels are doing. This monitoring is what determines your medication doses and the timing of the trigger.
• Trigger injection – the final injection, given at a precise time, that completes the maturation of the eggs inside the follicles and sets the clock for egg collection roughly a day and a half later. It contains either hCG or a GnRH agonist, or sometimes both. Timing matters, which is why clinics are exact about the hour.
• OHSS (ovarian hyperstimulation syndrome) – an exaggerated response of the ovaries to stimulation medication, in which the ovaries enlarge and fluid shifts into the abdomen. It ranges from mild bloating and discomfort to a serious condition requiring hospital care. Clinics manage the risk through drug choice, dose, trigger type and sometimes by freezing all embryos rather than transferring in that cycle. The HFEA lists it among the recognised risks of fertility treatment.

Egg collection and fertilisation

• Egg collection – the day procedure in which eggs are retrieved from the follicles using a fine needle passed through the vaginal wall under ultrasound guidance, usually under sedation or general anaesthetic. Australian clinics generally call this egg collection or oocyte pick-up (OPU); overseas material often calls the same procedure egg retrieval.
• IVF (in vitro fertilisation) – the treatment in which eggs are collected and combined with sperm in the laboratory, and a resulting embryo is later placed into the uterus. In vitro means in glass, and refers to the fertilisation happening outside the body. Strictly, IVF refers to that laboratory step, although in ordinary use it names the whole treatment.
• Conventional insemination – the standard IVF laboratory method, in which prepared sperm are placed in a dish with each egg and fertilisation is left to occur on its own. Sometimes called standard IVF or simply IVF, to distinguish it from ICSI.
• ICSI (intracytoplasmic sperm injection) – a laboratory technique in which a single sperm is injected directly into an egg using a fine glass needle. The HFEA describes it as most commonly used where sperm quality is a factor, or where conventional insemination has previously failed. It addresses getting the sperm into the egg; it does not create eggs or sperm that were not there.
• Fertilisation rate – the proportion of collected eggs that fertilise normally in the laboratory. Not every egg collected is mature, and not every mature egg fertilises, which is why the number of embryos is almost always smaller than the number of eggs collected. This drop-off is normal and expected, though it is one of the harder parts of the process to hear about over the phone.

Sperm and male factor terms

• Male factor infertility – infertility in which a problem with sperm production, sperm function or sperm delivery is identified as a contributing cause. It is a common finding, either alone or alongside a female factor, and it is assessed initially through a semen analysis.
• Sperm motility – the proportion of sperm in a sample that are moving, and how well they are moving. Laboratories usually grade movement into categories such as progressive motility, where sperm move forwards, and non-progressive motility, where they move without making progress.
• Sperm morphology – the proportion of sperm in a sample that have a normal shape when assessed under the microscope against defined criteria. Because the criteria are strict, the percentage judged normal is low even in fertile men, so this result in particular should be interpreted by the clinic rather than read at face value.
• Sperm DNA fragmentation – breaks in the genetic material carried inside sperm, measured by specialised tests that are not part of a standard semen analysis. Testing is offered by some clinics and not others, and its role in routine practice remains debated: there is no consensus that the result changes management for most couples. Ask your specialist what a result would actually alter before agreeing to the test.

Embryos, grading and transfer

• Cleavage stage – the early stage of embryo development, roughly days two and three after fertilisation, when the embryo is dividing into a small number of cells without yet growing in overall size. A day three embryo is a cleavage-stage embryo.
• Blastocyst – the stage an embryo reaches at around day five or six after fertilisation, when it has organised into a fluid-filled cavity with two distinct cell populations: an inner cell mass that would form the fetus, and a trophectoderm that would form the placenta. Not every embryo reaches this stage in the laboratory.
• Embryo grading – the laboratory's assessment of an embryo's appearance under the microscope, used to decide which embryo to transfer or freeze first. Cleavage-stage embryos are usually graded on cell number and fragmentation; blastocysts on expansion and on the appearance of the two cell populations. Grading systems differ between clinics, so a grade only compares embryos within the same laboratory, and a good grade is a prediction rather than a guarantee.
• Day 3 versus day 5 transfer – whether the embryo is transferred at cleavage stage or grown on to blastocyst first. Growing embryos to day five allows more selection between them, but not all embryos survive to that point, so clinics weigh the benefit of selection against the number of embryos available. Which is chosen depends on your embryo numbers and your clinic's laboratory practice.
• Embryo transfer – the procedure in which an embryo is passed through the cervix into the uterus using a fine catheter, usually with ultrasound guidance. It generally takes only a few minutes, does not normally require anaesthetic, and feels for most people similar to a cervical screening test.
• Fresh transfer – transfer of an embryo in the same cycle as the egg collection, without freezing, typically two to six days afterwards.
• Frozen embryo transfer (FET) – transfer of an embryo that was frozen and later thawed, in a separate cycle. The lining may be prepared with medication, or the transfer may be timed to your natural ovulation. A freeze-all cycle is one in which no fresh transfer is planned and every suitable embryo is frozen for later.
• Vitrification – the rapid freezing method now used for eggs and embryos, which cools them so quickly that they solidify without forming damaging ice crystals. It replaced the older slow-freezing method and is the reason frozen embryo transfer has become routine.
• Endometrial lining – the endometrium, the layer inside the uterus that thickens through the cycle and into which an embryo implants. It is measured on ultrasound before transfer, and clinics look at both its thickness and its pattern.
• Endometrial receptivity – the concept of a limited window during which the endometrium is able to accept an implanting embryo, often called the window of implantation. Tests that claim to identify this window for an individual patient are commercially available but contested: the HFEA rates endometrial receptivity testing red, meaning that on balance the evidence indicates it may reduce treatment effectiveness.

After the transfer: the wait and the tests

• Luteal phase – the part of the cycle between ovulation and either a period or a positive pregnancy test, during which progesterone from the corpus luteum maintains the uterine lining. In IVF, this phase is usually supported with medication because the collection procedure and the drugs used can disturb the body's own progesterone production.
• Luteal support – the progesterone, and sometimes oestrogen, prescribed after egg collection or before a frozen transfer to maintain the lining. It is given as pessaries, gel, injections or tablets depending on the clinic, and is normally continued past the pregnancy test until your clinic tells you to stop.
• Two-week wait – the interval between embryo transfer and the blood pregnancy test, in practice usually somewhat under two weeks. There is no monitoring during it, which is what most people find difficult about it, and neither the presence nor the absence of symptoms during this period reliably predicts the result.
• Implantation – the process by which an embryo attaches to and embeds in the endometrium, after which it begins producing hCG. It cannot be observed or felt, and the first evidence of it is the blood test.
• Beta hCG – the blood test that measures hCG quantitatively, used as the pregnancy test after transfer because it detects pregnancy earlier and more precisely than a urine test. It is often repeated a couple of days later, because how the number changes over time tells the clinic more than any single value.
• Biochemical pregnancy – a pregnancy detected only by a positive hCG result, which then ends before anything can be seen on ultrasound. It is a very early miscarriage. The term describes what could be measured, not a failure of anything you did.
• Clinical pregnancy – a pregnancy confirmed by ultrasound visualisation of a gestational sac, rather than by a blood test alone. This is the point at which clinics and registries count a pregnancy as clinical, and it is the outcome most commonly reported in research papers.
• Live birth rate – the proportion of cycles, or of transfers, that result in the birth of a living baby. It is the outcome that matters most to patients and the one most often missing from published figures, which frequently report clinical pregnancy instead. Always check which outcome a quoted percentage refers to, and what it is a percentage of.
• Cumulative live birth rate – the chance of a live birth across a full egg collection cycle, counting the fresh transfer and all subsequent frozen transfers of embryos from that same collection, rather than the result of one transfer alone. It is usually the more meaningful figure, because a single egg collection can produce several transfers. Australian and New Zealand figures are compiled in ANZARD, the national registry run by UNSW's National Perinatal Epidemiology and Statistics Unit with the Fertility Society of Australia and New Zealand, and are published for patients at Your IVF Success.

Genetic testing of embryos

• PGT-A (preimplantation genetic testing for aneuploidy) – testing a small biopsy of cells from an embryo to check whether it has the expected number of chromosomes. The HFEA defines aneuploid embryos as those with missing or extra chromosomes, which have less chance of developing into a baby. For most patients the HFEA rates PGT-A red, noting that it is a selection tool that often reduces the number of embryos available for transfer and that time to a live birth may be longer. It is offered widely in Australia and it is not a routine part of IVF.
• PGT-M (preimplantation genetic testing for monogenic disorders) – testing embryos for a specific inherited single-gene condition that is already known to run in the family, such as cystic fibrosis or Huntington's disease. Unlike PGT-A it is targeted at a known variant, is arranged case by case, and generally involves genetic counselling before treatment begins.
• Mosaicism – the finding that an embryo biopsy contains both chromosomally normal and abnormal cells. It complicates the interpretation of PGT-A, because a biopsy takes only a few cells from one part of the embryo and may not represent the whole. The HFEA notes that there are reports of healthy live births after transfer of a mosaic embryo, and flags the concern that viable embryos may be discarded. If PGT-A is offered to you, ask specifically how the clinic handles mosaic results.

Other treatment paths and donor terms

• IUI (intrauterine insemination) – a treatment in which prepared sperm are placed directly into the uterus through a fine catheter around the time of ovulation, either in a natural cycle or with mild stimulation. It is less invasive and less expensive than IVF, and it does not involve egg collection or a laboratory fertilisation step. See the HFEA's description of IUI.
• Donor egg – an egg donated by another person and fertilised with the recipient's partner's sperm or with donor sperm. In Australia, donation is altruistic rather than paid, donors are identifiable to donor-conceived people once they reach adulthood, and counselling is a required part of the process for everyone involved.
• Donor sperm – sperm donated by another person, used in IUI or IVF. The same Australian rules on non-commercial donation, identity-release and mandatory counselling apply.
• Unexplained infertility – the diagnosis given when standard investigations, typically ovulation testing, tubal assessment and semen analysis, return normal results and no cause is found. It means the available tests have not identified a reason, not that there is no reason. It is a common diagnosis and it does not mean nothing can be done.

Conditions you may hear named

• PCOS (polycystic ovary syndrome) – a common endocrine condition diagnosed on a combination of irregular or absent ovulation, clinical or biochemical signs of raised androgens, and polycystic ovarian morphology on ultrasound, once other causes have been excluded. In fertility care it matters mainly because ovulation is irregular and because a high antral follicle count raises the risk of OHSS during stimulation.
• Endometriosis – a condition in which tissue resembling the lining of the uterus grows outside the uterus, causing inflammation, pain and adhesions. It is associated with reduced fertility, though the relationship is not straightforward and many people with endometriosis conceive without assistance. Diagnosis and management in Australia follow national guidance and usually involve a gynaecologist.
• Adenomyosis – a related but distinct condition in which endometrial-type tissue is found within the muscular wall of the uterus itself, typically causing heavy periods, pain and an enlarged uterus. It is increasingly identified on imaging rather than only after surgery, and it can coexist with endometriosis.
• Hydrosalpinx – a fallopian tube that is blocked at its outer end and distended with fluid. It is relevant to IVF specifically because the fluid can pass back into the uterine cavity, and it is a recognised reason a specialist may recommend surgical treatment of the tube before proceeding with transfer.

Add-ons and contested tests

• IVF add-ons – optional extras offered alongside standard IVF, usually at additional cost, which are said to improve the chance of a baby. The HFEA maintains a traffic-light rating system that grades each add-on by the strength of the evidence behind it: green for effective on high-quality evidence, yellow where effectiveness is unclear, grey where there is insufficient evidence, black where good evidence shows no effect, and red where there are safety concerns or evidence of reduced effectiveness. It is worth reading before agreeing to anything beyond the standard cycle, and worth asking your specialist what rating an add-on carries and why they are recommending it anyway.
• Natural killer (NK) cells – immune cells found in the blood and, in a different specialised form, in the lining of the uterus. Blood NK cell testing is marketed as an explanation for implantation failure and recurrent miscarriage. The HFEA's position is direct: there is no convincing evidence that any maternal immune cells cause pregnancy failure, and because these tests look at NK cells in the blood rather than the distinct NK cells in the uterus, they offer no useful information about pregnancy outcomes.
• Immune testing and immune treatment – a group of tests and therapies based on the idea that an immune response prevents implantation, including steroids, intravenous immunoglobulin (IVIG), intralipids and TNF-alpha inhibitors. The HFEA rates these as red for steroids and IVIG and grey for intralipids, and states that the good evidence to date shows a risk of considerable harm without any increase in the chance of having a baby. This is an area where what is offered commercially and what the evidence supports are some distance apart.

Evidence and research terms

These four are not clinical terms, but you will meet them the moment you start reading about treatment options, and they determine how much weight a given claim deserves.

• Randomised controlled trial (RCT) – a study in which participants are allocated by chance to receive one treatment or another, so that the groups are comparable and the difference in outcome can reasonably be attributed to the treatment. Randomisation is what separates a trial from an observation that people who did X seemed to do better.
• Systematic review – a study of studies. Researchers define a question, search the literature according to a stated protocol, appraise each eligible study and, where the studies are similar enough, combine their results statistically in a meta-analysis. A good systematic review also reports how certain the pooled evidence is, using a framework such as GRADE. A review is only as reliable as the trials inside it.
• Sham (placebo) acupuncture – the control condition used in acupuncture trials, most often a blunt, retractable needle that touches the skin without penetrating it, so participants cannot tell which group they are in. It matters because it separates the effect of needling from the effect of attention, rest and expectation. In the 2013 Cochrane review of acupuncture in assisted conception, live birth favoured acupuncture in the trials that had no sham control (OR 1.55, 95% CI 1.14 to 2.12) but not in the sham-controlled trials (OR 1.03, 95% CI 0.67 to 1.58). The largest sham-controlled trial, run at 16 IVF centres in Australia and New Zealand and published in JAMA in 2018, found no significant difference in live births between real and sham acupuncture (18.3% versus 17.8%).
• Confidence interval (CI) – the range within which the true effect is likely to lie, given the data. For a ratio such as an odds ratio or risk ratio, an interval that crosses 1 means the result is compatible with no effect at all. This is why a headline figure quoted without its interval tells you very little.