Egg freezing glossary: medical and financial terms explained

AFC (antral follicle count)

The number of small follicles visible in the ovaries on a baseline transvaginal ultrasound, typically performed in the early follicular phase. AFC is a key predictor of how many mature eggs a stimulation cycle will yield.

AMH (anti-Müllerian hormone)

A hormone secreted by ovarian follicles. AMH levels reflect ovarian reserve and predict the response to stimulation. Higher AMH usually correlates with higher yield per cycle. Low AMH may push the protocol towards higher gonadotropin dose.

Antagonist protocol

The most common egg freezing stimulation protocol (around 70% of cycles). Stimulation medications begin on cycle day 2 or 3; the antagonist (Cetrotide or Ganirelix) is added around day 5 or 6 to prevent premature ovulation. Total stimulation duration 8 to 12 days.

Blastocyst

An early-stage embryo at day 5 or 6 of development, typically used for embryo transfer. After egg thaw and ICSI fertilisation, embryos are usually cultured to blastocyst stage before transfer.

Cryopreservation

The general term for preserving cells or tissues at very low temperatures. Egg freezing uses vitrification, a specific cryopreservation method that flash-freezes to avoid ice crystal formation.

Deferred interest

A medical credit financing structure where interest is waived if the balance is paid in full by the promotional end date. If even $1 is owed at the deadline, retroactive interest is applied to the original principal from day one. Read the deferred-interest clause carefully before agreeing.

Donor eggs

Eggs provided by a third-party donor (anonymous or known). Donor eggs are typically used when a patient's own eggs are not viable due to age, medical history, or low ovarian reserve. Per-cycle success rates are higher with donor eggs because donor age is typically under 30.

Embryo

The fertilised egg after ICSI or conventional IVF. An embryo cultured to blastocyst stage is typically used for embryo transfer.

ERISA plan

A self-funded employer health plan regulated under the federal Employee Retirement Income Security Act. ERISA plans are not subject to state-level insurance mandates, including state fertility coverage mandates. Confirm with HR whether your plan is fully insured (state-regulated) or self-funded ERISA (federally regulated).

Fertility benefit

An employer-provided benefit covering some portion of fertility treatment cost, typically delivered through a third-party platform (Carrot, Progyny, Maven, WIN Fertility, Stork Club). Approximately 20% of large US employers offer this in 2026.

FSA (Flexible Spending Account)

An employer-sponsored pre-tax savings account for qualified medical expenses. Contribution limits are set by the IRS annually. FSA dollars can fund egg freezing where there is medical necessity recognised under IRS Publication 502.

FSH (follicle-stimulating hormone)

A pituitary hormone that stimulates ovarian follicle development. Recombinant FSH (Gonal-F, Follistim) is the primary stimulation medication in egg freezing protocols.

Gonadotropin

The class of hormones used to stimulate the ovaries during an egg freezing cycle. Includes FSH (Gonal-F, Follistim) and HMG (Menopur, which contains both FSH and LH activity).

hCG trigger

Human chorionic gonadotropin injected 36 hours before egg retrieval to mature the follicles. Ovidrel is the most common branded form. Lupron is sometimes used as an alternative trigger to reduce OHSS risk.

HSA (Health Savings Account)

A pre-tax savings account for qualified medical expenses, available to patients enrolled in a high-deductible health plan. 2026 contribution limits are $4,300 self-only and $8,550 family per IRS Revenue Procedure 2025-19.

Iatrogenic infertility

Infertility caused by medical treatment, such as chemotherapy, radiation, gender-affirming care, or certain surgeries. Iatrogenic infertility is increasingly covered by state mandates (Georgia HB 94, Florida 2026 rule, Minnesota HF 1758) and insurer policies.

ICSI (intracytoplasmic sperm injection)

A laboratory technique in which a single sperm is injected directly into each mature egg to achieve fertilisation. ICSI is the standard fertilisation method for previously-frozen eggs and adds $1,500 to $3,000 to the lifecycle cost.

IVF (in vitro fertilisation)

The full process of fertilising an egg with sperm in a laboratory and transferring the resulting embryo to the uterus. Egg freezing is the first half of IVF, separated in time from the use of those eggs.

LH (luteinising hormone)

A pituitary hormone that triggers ovulation. Antagonist medications (Cetrotide, Ganirelix) suppress LH during stimulation to prevent premature ovulation before retrieval.

Lifetime maximum

The total dollar amount an insurance plan or fertility benefit will pay across all qualifying treatments over the lifetime of coverage. Common ranges are $20,000 to $75,000 for fertility benefits. Some plans count storage and lifecycle cost towards the same maximum; verify with HR.

Mandate

A state law requiring health insurance plans to cover specified categories of treatment. State fertility mandates exist in 25 states plus DC; coverage scope varies. Self-funded ERISA plans are not subject to state mandates.

Medically necessary preservation

Egg, sperm, or embryo freezing required because of an upcoming medical treatment that would impair fertility (chemotherapy, radiation, gender-affirming care, certain surgeries). Increasingly covered by state mandates and insurer policies.

MII (metaphase II oocyte)

A mature egg, the developmental stage required for fertilisation. The egg freezing yield is typically reported as the number of MII eggs collected. Immature eggs (MI or GV stage) are usually not vitrified.

Oocyte

The medical term for an egg cell. "Mature oocyte" (MII) and "immature oocyte" (MI or GV) refer to developmental stages.

OHSS (ovarian hyperstimulation syndrome)

A complication of stimulation in which the ovaries respond excessively, causing fluid shifts and pain. Mild OHSS is common (10 to 30% of cycles). Severe OHSS requiring hospitalisation occurs in well under 1% of properly-managed antagonist protocol cycles.

PGT-A (preimplantation genetic testing for aneuploidy)

An optional embryo-stage genetic test for chromosomal abnormalities. Adds $3,000 to $6,000 for 1 to 8 embryos. The case for PGT-A is stronger when the freezer is older or recurrent miscarriage is a concern.

Retrieval

The procedure to collect eggs from the ovaries. Performed under sedation, transvaginal ultrasound-guided aspiration, lasting 20 to 30 minutes.

SART (Society for Assisted Reproductive Technology)

The professional society for US fertility clinics that publishes outcomes data on participating clinic programmes. SART data is the primary US source for clinic-level success rate transparency.

Stimulation

The phase of the egg freezing cycle during which gonadotropins are administered to develop multiple ovarian follicles simultaneously. Typically 8 to 14 days.

Trigger shot

The single injection given 36 hours before egg retrieval to mature the follicles. Most US clinics use hCG (Ovidrel) or a dual hCG-Lupron trigger.

Vitrification

The egg-freezing method that uses ultra-rapid cooling to glass-state without ice crystal formation. Vitrification has largely replaced slow-freeze methods since the early 2010s and is the current standard of care.

Related

• Process and timeline (where most clinical terms come up)
• Medication cost (drug names and protocols)
• Insurance coverage (financial terms)
• Financing (deferred interest, HSA, FSA)