Egg Freezing Glossary

Understanding the language of egg freezing

Egg freezing can introduce a lot of new and unfamiliar terms. It’s completely normal to feel unsure about what everything means.

This glossary is designed to give you clear, simple explanations of the most common words you might come across when exploring egg freezing, going through treatment, or thinking about using your eggs.

You don’t need to learn everything at once. Use this as a guide, come back to it when you need to, and speak to your clinic or an Egg Advisor if anything is unclear.

A

AMH (Anti-Müllerian Hormone)
A hormone measured in a blood test that gives an indication of your ovarian reserve (how many eggs you may have remaining).

Aneuploidy
A condition where an egg or embryo has an abnormal number of chromosomes, which can affect the chances of pregnancy.

ART (Assisted Reproductive Technology)
A general term for medical treatments that help people have a baby, including IVF and egg freezing. 

B

Blastocyst
An embryo that has developed for around 5–6 days. This stage is often used for embryo transfer. 

C

Cryobank
A facility where frozen eggs, sperm, or embryos are stored.

Cryoprotectant
A substance used to protect eggs during freezing and thawing. 

E

Egg (Oocyte)
A female reproductive cell that can be fertilised by sperm to create an embryo.

Egg Freezing (Oocyte Cryopreservation)
The process of collecting, freezing, and storing eggs for possible use in the future.

Egg Quality
How likely an egg is to develop into a healthy embryo. This is closely linked to age.

Egg Quantity (Ovarian Reserve)
The number of eggs remaining in the ovaries.

Embryo
A fertilised egg that begins to develop into a baby.

Embryo Transfer
Placing an embryo into the uterus during IVF treatment.

Embryo Freezing (Embryo Cryopreservation)
Freezing embryos for future use.

Endometrial Preparation
Preparing the lining of the uterus to support implantation.

Estradiol
A hormone (estrogen) measured during treatment to monitor how the ovaries are responding. 

F

Follicle
A small fluid-filled sac in the ovary that contains an egg.

FSH (Follicle-Stimulating Hormone)
A hormone that helps eggs grow. Higher levels can suggest a lower ovarian reserve.

Fertilisation Rate
The proportion of eggs that successfully fertilise after treatment. 

H

Hormone Stimulation
Medications used to encourage the ovaries to produce multiple eggs during a treatment cycle.

I

ICSI (Intracytoplasmic Sperm Injection)
A technique where a single sperm is injected directly into an egg to help fertilisation. Often used with frozen eggs.

Implantation
When an embryo attaches to the lining of the uterus.

IVF (In Vitro Fertilisation)
A treatment where eggs are fertilised with sperm in a lab to create embryos.

L

LH (Luteinising Hormone)
A hormone that triggers ovulation (the release of an egg).

Live Birth Rate
The chance of having a baby following treatment.

O

Ovarian Reserve
A term used to describe the number and quality of eggs available.

OHSS (Ovarian Hyperstimulation Syndrome)
A rare side effect of fertility medication where the ovaries become swollen and uncomfortable.

R

Retrieval (Egg Collection)
A short medical procedure where eggs are collected from the ovaries.

S

Sperm Donation
Using sperm from a donor to help create embryos.

Slow Freezing
An older freezing method that has largely been replaced by vitrification. 

T

Thawing (Warming)
The process of warming frozen eggs so they can be used. Not all eggs survive this process.

V

Vaginal Ultrasound
A scan used to monitor the ovaries and developing follicles during treatment.

Vitrification
A fast freezing method that improves the survival of eggs by preventing ice crystal formation.

Viral Testing
Tests carried out to ensure eggs and sperm are safe to use.

Additional Useful Terms

Cycle
One full round of fertility treatment.

Egg Survival Rate
The percentage of eggs that survive the thawing process.

Final note

It’s completely normal to feel overwhelmed by the language used in fertility care.

Understanding these terms can help you feel more informed and confident—but you don’t have to navigate this alone. If you’d like support understanding what these terms mean for your own situation, you can explore our tools or speak to an Egg Advisor.