EggFreezingFacts.org

Egg Freezing Terms Explained

Egg freezing terms, medical and financial, in plain English. Each entry links to the page where the term does real work rather than sitting in a glossary.
AFC (antral follicle count)
AFC stands for antral follicle count. It measures the small follicles seen in the ovaries during a baseline transvaginal ultrasound performed early in the follicular phase (the start of your cycle). This number is a strong predictor of how many mature eggs a stimulation cycle will yield.
AMH (anti-Müllerian hormone)
A hormone released by ovarian follicles. AMH levels reflect ovarian reserve and predict how your ovaries will respond to stimulation. Higher AMH usually means more eggs per cycle. Low AMH may mean using a higher dose of stimulation hormones.
Antagonist protocol
The most common egg freezing stimulation protocol (used in about 70% of cycles). You start stimulation drugs on cycle day 2 or 3. You add the antagonist (Cetrotide or Ganirelix) around day 5 or 6 to stop early ovulation. The whole stimulation lasts 8 to 12 days.
Blastocyst
A blastocyst is a day 5 or 6 embryo typically used for transfer. After thawing eggs and performing ICSI fertilization, embryos are usually cultured to the blastocyst stage before transfer.
Cryopreservation
Vitrification is the cryopreservation technique used for egg freezing; it flash-freezes to avoid ice crystals. Cryopreservation is the broader term for preserving cells or tissues at very low temperatures.
Deferred interest
If you owe even $1 at the promotional end date, interest is added back from day one on the full borrowed amount. This deferred-interest plan waives interest only if you pay the full balance by the deadline. Read the terms carefully.
Donor eggs
Donor eggs come from an anonymous or known third party. They are typically employed when a patient's eggs are unviable due to age, medical factors, or diminished reserve. Since donors are usually under 30, per-cycle success rates are higher.
Embryo
The fertilized egg after ICSI or standard IVF. An embryo grown to blastocyst stage is typically used for transfer.
ERISA plan
The federal Employee Retirement Income Security Act regulates self-funded employer health plans, known as ERISA plans. State insurance mandates, including fertility coverage requirements, do not apply to these plans. Ask your HR: is your plan fully insured (state-regulated) or self-funded ERISA (federally regulated)?
Fertility benefit
A fertility benefit from an employer covers some treatment costs. This benefit usually comes through a third-party platform like Carrot, Progynyn, Maven, WIN Fertility, or Stork Club. About 20% of large US employers offer this in 2026.
FSA (Flexible Spending Account)
FSA stands for a type of employer-sponsored pre-tax savings account used for qualified medical expenses. Contribution limits are set annually by the IRS. Under IRS Publication 502, FSA dollars can fund egg freezing if there is medical necessity.
FSH (follicle-stimulating hormone)
The pituitary gland produces FSH, a hormone that helps ovarian follicles grow. In egg freezing protocols, the main stimulation drug is recombinant FSH, sold as Gonal-F or Follistim.
Gonadotropin
During an egg freezing cycle, a group of hormones stimulates the ovaries. These include FSH (brands Gonal-F, Follistim) and HMG (Menopur, which provides both FSH and LH activity).
hCG trigger
Administered 36 hours before retrieval, an hCG shot (often Ovidrel) matures follicles. Lupron may serve as an alternative trigger to reduce OHSS risk.
HSA (Health Savings Account)
Per IRS Revenue Procedure 2025-19, 2026 HSA contribution limits are $4,400 for self-only and $8,750 for family coverage. An HSA is a pre-tax savings account for qualified medical expenses, but you must be enrolled in a high-deductible health plan to use it.
Iatrogenic infertility
Medical treatments like chemotherapy, radiation, gender-affirming care, or certain surgeries can cause infertility. State mandates (Georgia HB 94, Florida 2026 rule) and insurer policies increasingly cover it.
ICSI (intracytoplasmic sperm injection)
For previously-frozen eggs, the standard ICSI technique directly injects a single sperm into each mature egg for fertilization. This adds $1,500 to $3,000 to the lifecycle cost.
IVF (in vitro fertilization)
Egg freezing is the opening half of IVF, with the rest deferred until you choose to use the eggs. The remainder is fertilizing an egg with sperm in the lab, then transferring the embryo that results into the uterus.
LH (luteinizing hormone)
Antagonist drugs (Cetrotide, Ganirelix) suppress LH during stimulation to stop premature ovulation before retrieval. This is done because LH is a pituitary hormone that triggers ovulation.
Lifetime maximum
A lifetime maximum is the total dollar amount an insurance plan or fertility benefit pays across all qualifying treatments. Fertility benefits commonly range from $20,000 to $75,000. Some plans apply storage and lifecycle costs toward that same cap; check with HR for details.
Mandate
Coverage scope varies by state, and 25 states plus DC have fertility mandates on the books. A state law compels health insurance plans to cover certain treatment categories, but the specifics differ. Self-funded ERISA plans are exempt from these state-level mandates.
Medically necessary preservation
Coverage for such freezing is increasingly provided by state mandates and insurer policies. When a medical treatment like chemotherapy, radiation, gender-affirming care, or certain surgeries threatens fertility, freezing eggs, sperm, or embryos may be necessary.
MII (metaphase II oocyte)
The number of MII eggs collected is typically how egg freezing yield is reported. A mature egg is one at the developmental stage needed for fertilization. Usually, immature eggs at the MI or GV stage are not vitrified.
Oocyte
An egg cell is medically termed an oocyte. Stages of development are indicated by 'mature oocyte' (MII) and 'immature oocyte' (MI or GV).
OHSS (ovarian hyperstimulation syndrome)
Mild OHSS occurs in 10 to 30% of cycles. Severe OHSS requiring hospital stay happens in well under 1% of properly-managed antagonist protocol cycles. OHSS is a complication of stimulation where the ovaries respond too much, causing fluid shifts and pain.
PGT-A (preimplantation genetic testing for aneuploidy)
An optional genetic test run on embryos to screen for chromosomal abnormalities, costing $3,000 to $6,000 for 1 to 8 embryos. It earns its place more clearly for older freezers, or where recurrent miscarriage is already a concern.
Retrieval
The egg retrieval procedure takes 20 to 30 minutes. It is done under sedation. A doctor uses a transvaginal ultrasound to guide a needle and aspirate (remove) the eggs.
SART (Society for Assisted Reproductive Technology)
SART publishes outcomes data from participating US fertility clinics. SART is the professional society for those clinics. SART data is the main US source for clinic-level success rate transparency.
Stimulation
The phase of the egg freezing cycle when gonadotropins are given to develop multiple ovarian follicles at once. Typically 8 to 14 days, depending on the protocol and how you respond.
Trigger shot
A single injection timed 36 hours ahead of retrieval, given to bring the follicles to maturity. hCG (Ovidrel) is the usual choice in US clinics, sometimes paired with Lupron as a dual trigger.
Vitrification
Vitrification is the current standard of care for egg freezing, using ultra-rapid cooling to turn cells into a glass-like state without ice crystal formation. It has largely replaced slow-freeze methods since the early 2010s.