Reference

IVF Glossary: Fertility Terms Explained A-Z

IVF terminology is bewildering. This IVF glossary defines the 57 most common fertility terms you'll meet during treatment, from AMH and blastocyst to ICSI, PGT-A and vitrification, in plain English. Search or jump straight to a letter below.

A B C D E F G H I K L M O P R S T V Z

A

AMH (Anti-Müllerian Hormone): A blood test that estimates ovarian reserve, how many eggs you have left. Higher values usually mean a stronger response to stimulation.
Andrologist: A doctor specialising in male reproductive health and sperm analysis.
Antagonist protocol: A common short IVF stimulation protocol (~10 days) using GnRH antagonist injections to prevent premature ovulation.
Antral follicle count (AFC): An ultrasound count of small follicles at the start of a cycle. Used alongside AMH to predict egg yield.
ART (Assisted Reproductive Technology): Umbrella term for fertility treatments that handle eggs, sperm or embryos outside the body, IVF, ICSI, IUI, egg/embryo donation.
Azoospermia: No sperm present in the ejaculate. May still allow fatherhood via TESA/TESE surgical sperm retrieval.

B

Beta hCG: Blood pregnancy test measuring hCG hormone. Done 10-14 days after embryo transfer.
Blastocyst: An embryo at day 5 or 6 of development, with around 100 cells. Blastocyst transfers generally have higher success rates than day-3 transfers.
BMI: Body Mass Index. Many clinics have BMI cut-offs (typically 30-35) for safety reasons before starting treatment.

C

Cleavage stage: An embryo at day 2 or 3, with 4-8 cells. Earlier and less informative than a blastocyst transfer.
CoQ10: A supplement sometimes recommended to support egg and sperm quality. Evidence is suggestive, not conclusive.
Cryopreservation: Freezing of eggs, sperm or embryos, usually by vitrification, for later use.
Cumulative success rate: Pregnancy rate across all transfers from one egg retrieval (fresh + frozen). A more honest measure than per-transfer rates.

D

Day 3 / Day 5 transfer: When the embryo is placed back in the uterus. Day 5 (blastocyst) is preferred when enough embryos develop.
Donor egg / sperm: Eggs or sperm from a third party. Anonymity laws vary by country (anonymous in Spain, Czech Republic, Greece; identifiable in the UK).
DOR (Diminished Ovarian Reserve): Lower egg quantity than expected for age. Often diagnosed via low AMH and AFC.
Double donation: Embryo created from both donor egg and donor sperm. Legal in many EU countries; restricted in others.
Down-regulation: First phase of a long IVF protocol, medication suppresses your natural cycle so the clinic can control stimulation.

E

Egg retrieval (OPU): A 15-20 minute sedated procedure to collect eggs from the ovaries through the vaginal wall.
Embryo donation: Receiving embryos donated by another couple who completed their family. Faster and cheaper than fresh donor cycles.
Embryo grading: Visual scoring of an embryo's appearance (e.g. 4AA, 3BB). Helpful but not a perfect predictor of success.
EmbryoScope: An incubator with a built-in camera that monitors embryo development without disturbing it. Often offered as an add-on.
Endometrium: The lining of the uterus. Needs to reach the right thickness (usually 7mm+) before transfer.
ESHRE: European Society of Human Reproduction and Embryology, issues European guidelines and clinic accreditation.

F

Fertilisation rate: Percentage of mature eggs that fertilise normally after insemination or ICSI. Healthy range: 60-80%.
Follicle: A fluid-filled sac in the ovary that contains an egg. Tracked by ultrasound during stimulation.
Frozen Embryo Transfer (FET): Transfer of a previously frozen and thawed embryo. Now often more successful than fresh transfers.
FSH (Follicle Stimulating Hormone): The hormone (natural or injected) that drives egg follicle growth.

G

Gonadotropins: Injectable fertility hormones (FSH/LH) used to stimulate the ovaries to produce multiple eggs.

H

hCG trigger: An injection (often Ovitrelle or Pregnyl) given ~36 hours before egg retrieval to mature the eggs.
HFEA: UK regulator (Human Fertilisation and Embryology Authority). Sets standards and publishes UK clinic data.
Hyperstimulation (OHSS): An over-response to stimulation drugs. Modern protocols make severe OHSS rare.

I

ICSI (Intracytoplasmic Sperm Injection): A single sperm is injected directly into an egg under a microscope. Used for male-factor infertility.
IUI (Intrauterine Insemination): Washed sperm placed directly into the uterus around ovulation. Lower cost, lower success than IVF.
IVF (In Vitro Fertilisation): Eggs are retrieved and fertilised with sperm in a lab; resulting embryos are transferred to the uterus.

K

Karyotype: A chromosome analysis of either parent. Sometimes ordered after recurrent miscarriage or failed cycles.

L

LH (Luteinising Hormone): Triggers ovulation naturally. Suppressed during stimulation; mimicked by the hCG trigger.
Luteal phase support: Progesterone (vaginal, oral or injection) given after transfer to support implantation.

M

Mock cycle: A trial run before a frozen transfer to confirm the lining responds correctly to the protocol.
Morphology: The shape and structure of sperm. One of three measures in a semen analysis.
Motility: How well sperm move. Progressive motility is the key value for natural conception or IUI.

O

OHSS (Ovarian Hyperstimulation Syndrome): An over-response to fertility drugs causing swollen, painful ovaries. Mild forms are common; severe forms rare.
Oocyte: Medical word for egg.

P

PCOS (Polycystic Ovary Syndrome): A common hormonal condition affecting ovulation. Often responds well to IVF with adjusted protocols.
PGT-A: Pre-implantation Genetic Testing for Aneuploidies, chromosome screening of embryos before transfer.
PGT-M: Pre-implantation Genetic Testing for Monogenic disorders, screening for a specific inherited condition.
Progesterone: The hormone that prepares and maintains the uterine lining for pregnancy. Supplemented after transfer.
Protocol: Your personalised medication plan for the cycle (long, short, antagonist, mini-IVF, natural cycle, etc.).

R

Reciprocal IVF (ROPA): Female same-sex couples where one partner provides the egg and the other carries the pregnancy.
Recurrent implantation failure (RIF): Multiple failed transfers of good-quality embryos. Often investigated with extra immune or uterine tests.

S

Stimulation (stims): The 10-12 day phase of daily injections to grow multiple follicles.
Surrogacy: Another woman carries the pregnancy. Illegal in most of Europe; legal status varies widely.

T

TESA / TESE / micro-TESE: Surgical sperm retrieval techniques used when sperm cannot be obtained from ejaculate.
Trigger shot: See hCG trigger. Final maturation injection before egg collection.
Two-week wait (2WW): The 10-14 days between transfer and the beta hCG blood test. The hardest part for most patients.

V

Vitrification: Ultra-fast freezing technique with very high survival rates. Now standard for eggs and embryos.

Z

Zygote: A fertilised egg in its first 24 hours, before it begins to divide.

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This glossary is for general education only and does not replace medical advice. Always discuss your specific situation with a qualified fertility specialist.