1. Why these abbreviations are important to understand first

In the process of receiving treatment for assisted reproduction, communication efficiency depends largely on having a common understanding of terms and abbreviations. Doctors use abbreviations in outpatient consultations because these terms have been widely agreed upon within the industry. However, if patients don't understand these abbreviations, they may make mistakes in three key areas:; they may misunderstand the treatment plan."

These abbreviations can be categorized into four categories:; (COS, OHSS, HCG); (ICSI, PGT, ET/FET); (AMH, AFC, ERA); (LBR)

Using this framework makes it easier to remember these abbreviations than trying to memorize them individually.

; (Controlled Ovarian Hyperstimulation)
In a natural cycle, a woman usually only has one follicle that develops and ovulates each month. COS involves using exogenous gonadotropins to stimulate multiple follicles to grow simultaneously during one cycle. This allows for the retrieval of multiple eggs during one procedure.

Fertilization, culture, screening, and transplantation all require careful consideration when making decisions. The key word here is "control" – the goal is to ensure that everything is controllable, monitorable, and adjustable, rather than allowing uncontrolled expansion.

2. HCG(Human Chorionic Gonadotropin)
This is a parameter that is important throughout the entire cycle. At the end of the cycle, it serves as a "night injection" to simulate the natural peak in LH levels, allowing the egg to reach its final maturity. This timing is crucial for egg retrieval 34–36 hours later. After transplantation, HCG levels become a critical indicator for determining pregnancy. This abbreviation refers to two completely different applications, which are easily confused by beginners.

3. OHSS(Ovarian Hyperstimulation Syndrome)
This is one of the most serious complications that can occur during ovulation stimulation. It occurs when the ovaries respond excessively to the medication, leading to increased vascular permeability and fluid leakage. Symptoms include abdominal distension, increased abdominal circumference, nausea, and decreased urine output. In severe cases, pleural and peritoneal effusion and electrolyte imbalances may occur. The key to prevention in clinical practice is early identification:

During the later stages of ovulation stimulation and after egg retrieval, it's important to record daily weight, abdominal circumference, and urine output as prescribed by your doctor. If there is a significant increase in weight or a significant decrease in urine output within a short period, you should report this to your doctor immediately, rather than waiting until the symptoms become unbearable.

III. Fertilization and Embryo Stage: From an Egg to a Transferable Embryo

4. ICSI(Intracytoplasmic Sperm Injection)
Conventional in vitro fertilization involves allowing sperm and eggs to combine freely in the culture medium. ICSI, on the other hand, involves injecting a single sperm directly into the egg's cytoplasm under a microscope. This bypasses the natural process of sperm penetration. It's often referred to as "second-generation IVF." ICSI is typically used when the man's semen parameters are severely abnormal (such as low sperm count or abnormal sperm morphology), when previous attempts at fertilization have failed, or when surgical sperm extraction is necessary (e.g., testicular/epididymal sperm extraction). It's important to note that ICSI addresses the issue of sperm-egg combination, but it does not improve egg quality or the frequency of normal chromosome patterns in embryos.

5. PGT(Preimplantation Genetic Testing)

At the blastocyst stage, a small amount of trophoblast cells are taken for genetic analysis. This technique is commonly referred to as "third-generation IVF." It isn't a single procedure but consists of three categories based on the objectives of testing:

• **PGT-A**: Tests whether the chromosome number is diploid, and eliminates abnormalities such as trisomies and monosomies.
• **PGT-M**: Used for known single-gene genetic disorders (e.g., thalassemia, spinal muscular atrophy), where both spouses must carry the same disease-causing gene.
• **PGT-SR**: Designed for chromosomal structural abnormalities, such as balanced translocations and inversions. It's suitable when either or both partners carry such abnormalities.

These three techniques serve different purposes and are not interchangeable. Misunderstanding "PGT" as meaning that all genetic issues have been tested is a common misconception in medical communication.

**6. ET/FET** (Embryo Transfer/Frozen Embryo Transfer)
ET involves transferring fresh embryos directly during the same cycle after egg retrieval. FET involves freezing embryos until the body condition and endometrial conditions are suitable for transfer in subsequent cycles. The choice between these methods depends on factors like the size of the ovaries and hormone levels after egg retrieval, whether the endometrium is suitable, whether PGT results need to be waited for, and whether there is a risk of OHSS. FET doesn't mean worse outcomes; in certain situations, it can even optimize the compatibility between the endometrium and embryo development stages.

**IV. Evaluation and Monitoring: Determining Ovarian Reserve and Implantation Window**

**7. AMH** (Anti-Müllerian Hormone)
Released by small ovarian follicles, AMH is the most commonly used serological marker for assessing ovarian reserve. It isn't affected by the menstrual cycle, and blood tests can be done at any time. Low levels indicate fewer available follicles and lower expected egg counts. Higher doses or different protocols may be required during ovulation induction. But it's important to note that:

g>AMH reflects the "amount of follicular reserve," not the "quality of eggs," and certainly not the ability to conceive. Clinically, there are many cases where AMH levels are low yet pregnancy occurs successfully. Conversely, there are cases where AMH levels are normal, but repeated failures occur due to chromosomal abnormalities in the embryos. AMH is a reference point for decision-making, not a definitive diagnosis.

8. AFC(Antral Follicle Count) – During early menstruation (usually on days 2–4), a transvaginal ultrasound is used to directly count the number of small antral follicles with a diameter of 2–10 mm in both ovaries. The relationship between AMH and AFC is complementary: if AMH is low while AFC is normal, or if AFC is low while AMH is within the normal range, it indicates that age and previous cycle outcomes should be considered together, rather than making conclusions based on a single value.

9. ERA(Endometrial Receptivity Analysis) – This test involves collecting a small sample of endometrial tissue and analyzing gene expressions related to receptivity. This helps determine whether the "implantation window" of the endometrium coincides with the usual timing, allowing for individualized adjustments to the transplantation timing. ERA is a valuable tool for identifying individuals who experience repeated implantation failures. However, it is not a routine procedure required for everyone. It's important to note that ERA only adjusts the "time window" and does not address issues such as endometrial thickness, blood flow, uterine cavity conditions, or chromosomal abnormalities in the embryos. Before undergoing this test, it's necessary to ensure that any potential causes of failure have been thoroughly investigated.

V. Evaluating Results: A Metric That Can Be Misinterpreted Easily

10. LBR(Live Birth Rate) – This refers to the proportion of live births achieved during a particular period. It's the most accurate indicator of actual outcomes in assisted reproduction. Other common metrics include the "clinical pregnancy rate" (based on the presence of a gestational sac detected by ultrasound) and the "biochemical pregnancy rate" (based on a temporary increase in HCG levels). There's a significant difference between these metrics: pregnancy doesn't mean the pregnancy will proceed smoothly throughout its early stages, nor does it mean that the pregnancy will result in a successful delivery. Therefore, when evaluating data from institutions, it's important to focus on the live birth rate and pay attention to three key factors: whether the statistics are based on "each transplantation cycle" or "each attempt at conception", which age group they refer to, and the time frame over which the data was collected.

VI. Keep a quick-reference table with you. It's more effective than memorization.

Abbreviation	Chinese Meaning	In One Sentence
COS	Controlled Superovulation	Allowing multiple follicles to grow simultaneously
HCG	Human Chorionic Gonadotropin	Use during the night injection to trigger maturation; blood test to determine pregnancy
OHSS	Ovarian Hyperstimulation Syndrome	Overly strong reaction; monitor weight and urine output
ICSI	Intracytoplasmic Sperm Injection	Second-generation IVF technique, involving single sperm injection
PGT	Preimplantation Genetic Testing	Third-generation IVF technique, divided into A, M, SR categories
ET / FET	Fresh Embryo Transfer / Frozen Embryo Transfer	Transfer during the current cycle / Transfer after freezing
AMH	Anti-Müllerian Hormone	Used to assess stock availability, not quality
AFC	Abscesses in Follicles	Used to count follicles

Basic number of follicles in the ovariansinus cavitySmall follicles detected during early menstruation via ultrasoundERA (Early Endometrial Receptivity)Analysis of endometrial receptivityWindow for testing when repeated failures have occurredLBR (Live Birth Rate)Rate of live birthsThe most important outcome indicator

The purpose of using terms like these is to improve communication efficiency, not to create barriers between people. Understanding these abbreviations isn't meant to turn you into a doctor on the spot. Instead, it helps you ask clear questions during those limited minutes spent with a doctor-what exactly is being tested? If the results are abnormal, what should be done next? Does this approach correspond to the reasons for my previous failures?

When information is clear, judgments can be made based on solid evidence. Leilava always advises that when receiving test results, don't immediately compare them with online conclusions. First, understand the abbreviations and their meanings, then discuss your specific concerns with the doctor. By doing this, many unnecessary anxieties and redundant tests can be avoided.