Fertility medicine comes with an alphabet soup of acronyms and jargon. This glossary covers every term you are likely to encounter — from your first consultation through embryo transfer and beyond. Bookmark this page and come back to it whenever a term throws you off.
A
AFC (Antral Follicle Count)
An ultrasound-based count of the small follicles visible on your ovaries at the start of a cycle. Gives your doctor an estimate of your egg supply. A count of 10–20 is typical for women under 35. Lower counts suggest diminished ovarian reserve. One of the key tests done before IVF.
AMH (Anti-Müllerian Hormone)
A blood test that estimates your ovarian reserve — how many eggs you have remaining. Higher AMH generally means more eggs available for IVF stimulation. Normal range varies by age: roughly 1.0–3.5 ng/mL for women 25–35. AMH does not measure egg quality, only quantity.
Agonist (GnRH Agonist)
A type of medication (e.g., Lupron/leuprolide) used in some IVF protocols to suppress your natural hormone cycle before stimulation begins. "Long protocol" or "down-regulation" cycles use agonists. They initially cause a surge of hormones before suppressing them.
Antagonist (GnRH Antagonist)
A medication (e.g., Cetrotide, Ganirelix) used during stimulation to prevent premature ovulation. Added mid-cycle when follicles reach a certain size. "Antagonist protocol" is the most common modern IVF protocol — shorter and with lower OHSS risk than agonist protocols.
Assisted Hatching
A lab technique where the embryologist makes a small opening in the embryo's outer shell (zona pellucida) before transfer, theoretically helping it implant. Evidence for its benefit is mixed — the HFEA rates it amber (insufficient evidence). Sometimes used for patients over 38 or with repeated implantation failure.
ART (Assisted Reproductive Technology)
The umbrella term for any medical procedure that handles eggs or embryos. Includes IVF, ICSI, egg freezing, embryo freezing, and donor procedures. IUI is technically not ART because it does not handle eggs or embryos — it only places sperm.
B
Beta (Beta hCG)
The blood test that confirms pregnancy after embryo transfer. Measures the hormone human chorionic gonadotropin (hCG), produced by a developing embryo after implantation. Typically done 10–14 days after transfer. A "positive beta" means you are pregnant. A "doubling beta" (repeat test 48 hours later showing the level has roughly doubled) is a positive sign.
Blastocyst
An embryo that has developed for 5–6 days after fertilisation and reached approximately 100+ cells. Blastocysts have differentiated into two parts: the inner cell mass (which becomes the baby) and the trophectoderm (which becomes the placenta). Most modern IVF programmes culture embryos to blastocyst stage before transfer or freezing.
Blighted Ovum (Anembryonic Pregnancy)
A pregnancy where a gestational sac develops but no embryo forms inside it. Results in a miscarriage. Detected by ultrasound. Usually caused by chromosomal abnormalities in the embryo. Not caused by anything the patient did.
C–D
Chemical Pregnancy
A very early pregnancy loss that occurs before the embryo is visible on ultrasound — typically around week 4–5. The beta hCG test is positive but drops rather than rising. Essentially an early miscarriage. Common in both natural and IVF pregnancies.
Clinical Pregnancy
A pregnancy confirmed by ultrasound showing a gestational sac (and ideally a heartbeat) — usually around 6–7 weeks. This is the standard definition used when clinics report "pregnancy rates." A clinical pregnancy can still result in miscarriage, which is why live birth rate is a more meaningful outcome measure.
Corpus Luteum
The structure left behind on the ovary after a follicle releases an egg. It produces progesterone, which supports early pregnancy. In IVF cycles with a "freeze-all" approach, there is no corpus luteum, so progesterone must be supplemented externally.
Cryopreservation
The process of freezing biological material — eggs, sperm, or embryos — for future use. Modern cryopreservation uses vitrification (flash freezing) rather than slow freezing, with survival rates above 95% for embryos.
DET (Double Embryo Transfer)
Transferring two embryos at once. Increases the chance of pregnancy per transfer but also increases the risk of twins (with associated complications). Most guidelines now recommend single embryo transfer (SET) when a good-quality blastocyst is available.
DOR (Diminished Ovarian Reserve)
A diagnosis indicating fewer remaining eggs than expected for your age. Determined by AMH, FSH, and AFC. Does not necessarily mean poor egg quality — it means fewer eggs are available for retrieval. May require higher medication doses or modified protocols.
E–F
E2 (Estradiol)
A form of oestrogen produced by growing follicles. Monitored via blood tests during stimulation. Rising E2 levels indicate follicles are developing and producing eggs. Very high levels can signal OHSS risk.
Egg Retrieval (Oocyte Retrieval)
The procedure where eggs are collected from the ovaries using a thin needle guided by ultrasound. Done under light sedation. Takes 15–30 minutes. Mildly uncomfortable afterward — most patients describe it as cramping similar to a heavy period. You can usually return to normal activity the next day.
Embryo Grading
A system embryologists use to assess embryo quality. Day 5 blastocysts are graded on expansion (1–6), inner cell mass quality (A–C), and trophectoderm quality (A–C). So "4AA" means a fully expanded blastocyst with excellent inner cell mass and trophectoderm. Higher grades generally correlate with higher implantation rates, but lower-grade embryos can and do produce healthy pregnancies.
ERA (Endometrial Receptivity Analysis)
A biopsy-based test that checks whether your uterine lining is receptive to embryo implantation at the standard transfer timing. If the test shows you are "pre-receptive" or "post-receptive," your transfer timing can be adjusted. Evidence for routine use is debated; may be useful after repeated implantation failure.
FET (Frozen Embryo Transfer)
A cycle where a previously frozen embryo is thawed and transferred to the uterus. No egg retrieval is needed — the cycle focuses on preparing the uterine lining. FET cycles are simpler, shorter (5–7 days in Colombia), and less expensive than a full IVF cycle. Success rates with frozen embryos now match or exceed fresh transfer rates.
Follicle
A fluid-filled sac on the ovary that contains a developing egg. During IVF stimulation, multiple follicles are encouraged to grow simultaneously. Follicle growth is tracked by ultrasound. Not every follicle contains a mature egg.
FSH (Follicle-Stimulating Hormone)
A hormone that stimulates follicle growth. Measured via blood test on cycle day 2–3 as part of baseline testing. High FSH (above 10 IU/L) can indicate diminished ovarian reserve. FSH-based medications (Gonal-F, Follistim) are the primary drugs used in IVF stimulation.
G–I
Gestational Carrier (Surrogate)
A woman who carries a pregnancy for intended parents using an embryo created from the intended parents' (or donors') gametes. The gestational carrier has no genetic relationship to the child. Distinct from "traditional surrogacy," where the surrogate provides the egg.
Gonadotropins
The injectable hormones used to stimulate the ovaries during IVF. Include FSH (Gonal-F, Follistim), LH (Luveris), or combined FSH+LH (Menopur). Administered as daily subcutaneous injections for 8–12 days during stimulation.
hCG (Human Chorionic Gonadotropin)
Two uses in IVF: (1) As a "trigger shot" to induce final egg maturation before retrieval; (2) As the hormone measured in a pregnancy test. Trigger brands include Ovidrel (recombinant) and Pregnyl (urinary-derived).
HSG (Hysterosalpingogram)
An X-ray procedure where dye is injected through the cervix to check whether the fallopian tubes are open and the uterine cavity is normal. Done before IVF to rule out hydrosalpinx (blocked, fluid-filled tubes) which can reduce implantation rates. Mildly uncomfortable but brief.
ICSI (Intracytoplasmic Sperm Injection)
A lab technique where a single sperm is injected directly into an egg using a microscopic needle. Originally developed for severe male factor infertility but now used in roughly 70% of all IVF cycles worldwide. In Colombia, ICSI is often included in the base IVF price.
Implantation
The process by which an embryo attaches to and embeds into the uterine lining. Occurs approximately 6–10 days after egg retrieval (1–5 days after a Day 5 transfer). Cannot be felt. Nothing you do or do not do after transfer significantly affects implantation — it is determined primarily by embryo quality and uterine receptivity.
IUI (Intrauterine Insemination)
A simpler fertility procedure where washed, concentrated sperm is placed directly into the uterus around the time of ovulation. Less invasive and less expensive than IVF but significantly lower success rates (10–20% per cycle). Often tried before IVF for unexplained infertility or mild male factor.
L–O
LH (Luteinising Hormone)
The hormone that triggers ovulation. In natural cycles, an LH surge causes the dominant follicle to release its egg. In IVF, LH is monitored to ensure premature ovulation does not occur before egg retrieval. Some stimulation protocols include LH supplementation.
Live Birth Rate
The percentage of cycles that result in a baby being born alive. The most meaningful measure of IVF success — more useful than pregnancy rate or clinical pregnancy rate, which do not account for miscarriage. Always ask for live birth rate when evaluating clinics.
Mosaic Embryo
An embryo where PGT-A testing finds a mix of normal and abnormal cells. Not fully aneuploid (abnormal) but not fully euploid (normal) either. Some mosaic embryos can produce healthy pregnancies, depending on the specific abnormality and the percentage of affected cells. Transfer decisions are made case-by-case.
OHSS (Ovarian Hyperstimulation Syndrome)
A potential side effect of ovarian stimulation where the ovaries over-respond to medications, becoming swollen and leaking fluid into the abdomen. Mild OHSS (bloating, discomfort) is relatively common. Severe OHSS (fluid in abdomen/chest, blood clots, kidney issues) is rare with modern protocols (~1–2%). Prevented by using antagonist protocols, lower medication doses, and GnRH agonist triggers.
Oocyte
The medical term for an egg cell. At retrieval, eggs are classified as mature (MII — ready for fertilisation), immature (MI or GV — may mature in the lab), or degenerate (non-viable). Only mature oocytes can be fertilised.
P–R
PGT-A (Preimplantation Genetic Testing for Aneuploidies)
A test performed on a small biopsy of cells from the embryo's trophectoderm (outer layer) to check for chromosomal abnormalities. Results classify embryos as euploid (normal), aneuploid (abnormal), or mosaic. Helps select embryos most likely to implant and result in a healthy pregnancy. Previously called PGS.
PGT-M (Preimplantation Genetic Testing for Monogenic Disorders)
Testing embryos for a specific known genetic condition carried by one or both parents — such as cystic fibrosis, sickle cell disease, or BRCA mutations. Requires advance preparation (creating a custom test probe for the family's specific mutation). Previously called PGD.
Progesterone
A hormone essential for preparing and maintaining the uterine lining for embryo implantation. After egg retrieval, progesterone levels drop because the follicles have been emptied. Supplemental progesterone (vaginal pessaries, intramuscular injections, or oral capsules) is given after transfer and continued through early pregnancy (typically 8–12 weeks).
RE (Reproductive Endocrinologist)
A doctor specialising in fertility — a subspecialist within OB/GYN. Board certification in reproductive endocrinology and infertility (REI) requires fellowship training beyond a standard OB/GYN residency. Your RE is the primary doctor managing your IVF cycle.
REDLARA
Red Latinoamericana de Reproducción Asistida — the Latin American registry for assisted reproduction. Member clinics report outcomes data annually. REDLARA accreditation indicates a clinic meets regional quality standards. The Latin American equivalent of ESHRE (Europe) or SART (US).
ROPA (Reception of Oocytes from the Partner)
A technique for lesbian couples where one partner provides the eggs and the other carries the pregnancy. Also called reciprocal IVF or shared motherhood. Both partners have a biological connection to the child. Available in Colombia and offered by clinics including Eugin.
S–Z
SART (Society for Assisted Reproductive Technology)
US-based professional organisation that publishes clinic-specific IVF success rate data. SART member clinics adhere to practice guidelines and report outcomes. Their online database allows patients to compare clinic results — though they explicitly warn against using the data to rank clinics due to patient selection differences.
SET (Single Embryo Transfer)
Transferring one embryo at a time. The standard recommendation when a good-quality blastocyst is available — reduces multiple pregnancy risk while maintaining high success rates. Cumulative success over multiple SET cycles often matches or exceeds DET success rates with much lower twin risk.
Stim (Stimulation)
Short for ovarian stimulation — the 8–14 day period of daily hormone injections designed to grow multiple follicles simultaneously. The core phase of an IVF cycle. Monitored by regular ultrasound and blood tests to track follicle growth and hormone levels.
Trigger Shot
An injection given 34–36 hours before egg retrieval to trigger final egg maturation. Timing is critical — retrieval must happen before the eggs ovulate naturally. Three types: hCG trigger (Ovidrel, Pregnyl), GnRH agonist trigger (Lupron), or dual trigger (both). GnRH agonist triggers significantly reduce OHSS risk.
TWW (Two-Week Wait)
The approximately 10–14 day period between embryo transfer and the beta hCG pregnancy test. Widely considered the most stressful part of IVF. There is nothing medical to do during this time except continue progesterone. Symptom-spotting is universal but unreliable — early pregnancy symptoms and progesterone side effects are identical.
Vitrification
A flash-freezing technique for eggs and embryos that prevents ice crystal formation (which damages cells). Has largely replaced older slow-freezing methods. Thaw survival rates with vitrification are 95%+ for embryos and 85–95% for eggs. The reason frozen embryo transfer success rates now match fresh.
Zona Pellucida
The protective outer shell surrounding an egg and early embryo. The embryo must hatch out of the zona pellucida to implant in the uterine lining. Assisted hatching involves creating an artificial opening in the zona to facilitate this process.
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