IVF glossary: 70 terms in plain English
Clinics talk in initials. This is the list you can open on your phone in the waiting room. One sentence for what it means, one for what it means for you.
A
- AMH (anti-Mullerian hormone)A hormone produced by small ovarian follicles, measured by blood test to estimate ovarian reserve.
- AneuploidyThe presence of an abnormal number of chromosomes in a cell, such as an embryo having too many or too few.
- Antral follicle count (AFC)The number of small resting follicles visible on an ultrasound scan of the ovaries, usually done early in the menstrual cycle.
- Assisted hatchingA lab technique that thins or opens the outer shell of an embryo before transfer, intended to help it hatch and implant.
- AzoospermiaThe complete absence of sperm in a semen sample.
B
- Beta hCGA blood test measuring the level of human chorionic gonadotropin, used to confirm and monitor early pregnancy after embryo transfer.
- Biochemical pregnancyA very early pregnancy confirmed only by a positive hCG blood test that does not continue to a stage where it can be seen on ultrasound.
- BlastocystAn embryo that has developed for about five to six days and formed a fluid-filled cavity with two distinct cell groups.
- Blastocyst gradingA system embryologists use to describe a blastocyst's expansion stage and the quality of its two main cell groups, usually written as a number and two letters.
C
- Clinical pregnancy rateThe proportion of treatment cycles or transfers that result in a pregnancy confirmed by ultrasound, typically showing a gestational sac or heartbeat.
- CryopreservationThe freezing and storage of eggs, sperm or embryos at very low temperatures for future use.
- Cumulative live birth rateThe chance of having a live birth after using all embryos from one egg collection, across a fresh transfer and any subsequent frozen transfers.
D
- Day 3 embryoAn embryo three days after fertilisation, typically consisting of six to ten cells.
- Day 5 blastocystA blastocyst-stage embryo cultured for five days after fertilisation, the most common stage at which embryos are transferred or frozen.
- Donor eggsEggs provided by a screened donor for use in another person's fertility treatment.
- Donor spermSperm provided by a screened donor for use in fertility treatment.
- DownregulationThe temporary suppression of the pituitary gland's hormone signals using an agonist drug, done before starting stimulation in a long protocol cycle.
E
- Ectopic pregnancyA pregnancy that implants outside the uterus, most commonly in a fallopian tube, and cannot continue safely.
- Egg collectionThe minor surgical procedure in which eggs are retrieved from the ovaries using a fine needle guided by ultrasound, usually under sedation.
- EmbryoA fertilised egg that has begun dividing and developing, from the day after fertilisation until roughly the end of the eighth week of pregnancy.
- Embryo glueA transfer medium containing hyaluronan, used to load the embryo into the catheter before transfer, marketed as helping the embryo attach to the womb lining.
- Embryo transferThe procedure in which an embryo is placed into the uterus using a fine catheter, usually without sedation.
- Endometrial scratchA procedure involving a small deliberate injury to the womb lining, done before an embryo transfer cycle, intended to encourage implantation.
- EndometriumThe lining of the uterus, which thickens across the menstrual cycle and is where an embryo implants.
- ERA test (endometrial receptivity analysis)A test that biopsies the womb lining to try to identify the optimal day for embryo transfer based on gene expression.
- Estradiol (E2)A form of oestrogen produced by growing follicles, measured by blood test to track response during ovarian stimulation.
F
- Fertilisation rateThe proportion of mature eggs that successfully fertilise after insemination or ICSI.
- FollicleA small fluid-filled sac in the ovary that contains a developing egg.
- Follicle trackingA series of ultrasound scans and blood tests during ovarian stimulation used to monitor follicle growth and hormone levels.
- Fresh transferAn embryo transfer carried out in the same cycle as the egg collection, without freezing the embryo first.
- Frozen embryo transfer (FET)An embryo transfer using an embryo that was previously frozen and is thawed for the procedure.
- FSH (follicle-stimulating hormone)A hormone that stimulates the growth of ovarian follicles, produced naturally by the pituitary gland and also given as an injectable medication during stimulation.
G
- GnRH (gonadotropin-releasing hormone)A hormone released by the hypothalamus that controls the pituitary gland's release of FSH and LH.
- GnRH agonistA medication that initially stimulates then suppresses the pituitary gland's release of hormones that trigger ovulation.
- GnRH antagonistA medication that quickly blocks the pituitary gland from releasing the hormone surge that triggers ovulation.
H
I
- ICSI (intracytoplasmic sperm injection)A fertilisation technique in which a single sperm is injected directly into an egg using a fine needle.
- ImplantationThe process by which a blastocyst attaches to and embeds itself in the lining of the uterus.
- IMSI (intracytoplasmic morphologically selected sperm injection)A variation of ICSI that uses very high magnification to examine sperm shape in more detail before selecting one for injection.
- Intralipid infusionAn intravenous fat emulsion infusion sometimes offered around embryo transfer, proposed as a way to modify immune activity in the womb.
- 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 before an embryo is transferred into the uterus.
L
- LH (luteinising hormone)A hormone that triggers ovulation and supports the corpus luteum's production of progesterone.
- Live birth rateThe proportion of treatment cycles or embryo transfers that result in the birth of at least one live baby.
- Luteal phase supportMedication, usually progesterone, given after egg collection or embryo transfer to support the womb lining ahead of implantation.
O
- OHSS (ovarian hyperstimulation syndrome)A condition in which the ovaries become swollen and painful in response to fertility hormones, ranging from mild to severe.
- OocyteThe medical term for an egg cell, the female reproductive cell that can be fertilised to form an embryo.
- Ovarian reserveThe number and quality of eggs remaining in the ovaries at a given time.
- Ovarian stimulationA course of injectable hormone medication used to encourage the ovaries to develop multiple follicles in one cycle.
P
- PCOS (polycystic ovary syndrome)A hormonal condition affecting ovulation, associated with multiple small follicles on the ovaries and, often, irregular periods.
- PESA/TESA (sperm aspiration procedures)Procedures using a fine needle to collect sperm directly from the epididymis (PESA) or testicle (TESA), used when sperm are absent from the ejaculate.
- PGT-A (preimplantation genetic testing for aneuploidy)A test on cells biopsied from an embryo to check for the correct number of chromosomes before transfer.
- PGT-M (preimplantation genetic testing for monogenic disorders)A test on cells biopsied from an embryo to check for a specific single-gene condition known to run in the family.
- PGT-SR (preimplantation genetic testing for structural rearrangements)A test on cells biopsied from an embryo to check for chromosome structural rearrangements, used when a parent carries a known chromosomal translocation.
- ProgesteroneA hormone that prepares and maintains the womb lining to support implantation and early pregnancy.
- ProlactinA hormone produced by the pituitary gland that can, when raised, interfere with ovulation.
S
- Semen analysisA laboratory test that measures sperm count, movement (motility) and shape (morphology) in a semen sample.
- Sperm DNA fragmentation testingA test that measures the proportion of sperm with breaks or damage in their DNA.
- Surgical sperm retrievalA minor surgical procedure to collect sperm directly from the testicle or epididymis, used when sperm can't be obtained through ejaculation.
T
- TestosteroneA hormone important for sperm production in men, sometimes measured as part of a male fertility assessment.
- Thyroid function (TSH)A blood test measuring thyroid stimulating hormone, used to check whether the thyroid gland is working within a normal range.
- Time-lapse imagingAn incubator system with a built-in camera that takes continuous images of developing embryos without removing them from the incubator.
- Treatment add-onsOptional extra procedures offered alongside standard IVF, rated by the HFEA on the strength of evidence that they improve outcomes.
- Trigger shotA single injection given near the end of stimulation to complete the final maturation of eggs before collection.
- Two week waitThe period of roughly two weeks between embryo transfer and the pregnancy blood test.
Written by patients, not clinicians. This page has not yet been reviewed by a named fertility professional, so it explains published guidance and points you to the original source instead of giving medical advice. It is not medical advice. Decisions about your treatment belong with your own clinic. Read our editorial policy and corrections policy.