Going through in-vitro fertilization (IVF) can be a complex and intimidating process. Your doctors or nurses may be using a bunch of terminology you’ve never heard of, and you may find that you often leave your fertility clinic appointments with your head spinning. To help you feel prepared for the IVF journey, we’ve created a glossary of the top 12 IVF terms you need to know.

1. Ovarian Reserve

What is it? The remaining supply of eggs in your ovaries.

What does it mean? When speaking with your fertility care team, the “ovarian reserve” may be referred to when talking about your fertility potential. If your ovarian reserve is high, you may have a better chance of responding to fertility treatments.

If your ovarian reserve is low, you should not delay very long before trying to conceive.

2. AMH (Anti-Müllerian hormone)

What Is It? An AMH test is often used to check your ability to produce eggs that can be fertilized for pregnancy. Some doctors believe this is the most important hormone for measuring ovarian reserve.

What Does It Mean? If you have higher AMH values, you will tend to have a better response to ovarian stimulation (see below) during IVF which could lead to having more eggs retrieved. In general, retrieving more eggs with IVF gives a higher success rate.

3. AFC (Antral Follicle Count)

What Is It? Antral follicles are small follicles (about 2-9 mm in diameter) in the ovary that can be seen, measured, and counted with ultrasound.

What Does It Mean? Antral follicle counts (along with female age) are a great tool for estimating your ovarian reserve, expected response to ovarian stimulation, and chance for successful pregnancy with in-vitro fertilization.

The number of antral follicles visible on ultrasound is indicative of the number of microscopic primordial follicles remaining in your ovaries. Each primordial follicle contains an immature egg that can potentially develop and ovulate in the future.

4. FSH (Follicle Stimulating Hormone)

What Is It? A hormone secreted by the anterior pituitary gland which promotes the formation of egg or sperm. In women, FSH helps control the menstrual cycle and stimulates the growth of eggs in the ovaries.

FSH levels in women change throughout the menstrual cycle, with the highest levels happening just before an egg is released by the ovary. This is known as your “ovulation.”

What Does It Mean? High FSH levels are usually a sign that your body is working harder than normal to produce and release an egg.

Elevated FSH can be problematic because women with elevated FSH often respond poorly to IVF fertility medications, which often means that the egg retrieval process yields few eggs. As a result, the prognosis for IVF patients using their own eggs can be very poor. Many fertility clinics have FSH cutoff levels beyond which they will not attempt IVF.

5. E2 (Estradiol)

What Is It? A form of estrogen, a female sex hormone that regulates many processes in your body. Women will have higher amounts of E2 during your reproductive years and almost none after menopause.

What Does It Mean? During IVF, when the follicles mature, the eggs secrete the E2 hormone. The more eggs or follicles present, the higher the E2 level. Measuring E2 levels in the blood can act as an indicator as to how well the ovaries are responding to the drugs.

6. Ovarian Stimulation

What Is It? During ovulation, you will receive an injection of medications for 8-14 days to induce the ovaries to generate as many mature eggs as possible. Oftentimes, this is self-administered.

What Does It Mean? The goal of ovarian stimulation is to harvest as many mature eggs as possible from your ovaries. This will maximize your chances one of the eggs can be fertilized and implanted back into the uterus.

7. ICSI (Intracytoplasmic Sperm Injection)

What Is It? The procedure in which a tiny needle, called a micropipette, is used to inject a single sperm into the center of the egg.

What Does It Mean? In order for a sperm to fertilize an egg, the head of the sperm must attach to the outside of the egg and push through the outer layer to the inside of the egg (cytoplasm), where fertilization happens.

There are many reasons why sperm may not be able to penetrate the outer layer. The ICSI process helps the sperm skip this step to fertilize the egg and become an embryo.

8. Euploid Embryo

What Is It? An embryo that contains the correct number of each chromosome.

What Does It Mean? In IVF, embryologists and physicians typically strive to transfer one euploid (normal) embryo that will have the best chance of becoming a healthy baby.

9. Aneuploid Embryo

What Is It? An embryo that carries an abnormal number of chromosomes.

What Does It Mean? Aneuploid embryos (abnormal) that don’t have the correct number of chromosomes can lead to increased rates of miscarriages, birth defects, and IVF failure.

10. PGT (Preimplantation Genetic Testing)

What Is It? PGT is the process of screening cells from embryos for genetic diseases and/or chromosomal disorders.

What Does It Mean? This test may be done in conjunction with IVF before the embryo transfer and pregnancy is established.

Various PGT tests can identify aneuploid embryos that could prevent successful outcomes. Other types of PGT can also identify the presence of more than 4,000 single-gene disorders, including cystic fibrosis, spinal muscular atrophy, and fragile X syndrome in couples who are found to be carriers of one of these genetic mutations.

Testing enables physicians to identify the embryos most likely to result in a healthy outcome following embryo transfer.

11. Endometrium

What Is It? The mucous membrane lining of the uterus, which thickens during your menstrual cycle in preparation for possible implantation of an embryo.

What Does It Mean? For women undergoing IVF, the thickness of this lining is very important. The fertility doctor will measure the thickness of the lining before the embryo transfer to ensure that it is sufficiently thick to allow for implantation.

A thick, receptive, nourishing uterine lining is the best possible environment for the embryo, and the ideal lining is at least 7 to 8mm thick and displays a “trilaminar” (or “three layered”) appearance on an ultrasound.

A too-thin uterine lining can be a serious problem in IVF, leading to failed implantation or display irregularity in their lining and early pregnancy loss.

There are several reasons why a woman might suffer from a thin lining. Some causes include:

• Estrogen deficiency
• Poor blood flow to the uterus
• Uterine fibroids
• Adhesions or scar tissue in the uterus, caused by trauma or infection

12. Endometrial Receptivity

What Is It? Endometrial receptivity is a complex process that provides the embryo with the opportunity to attach to the endometrium and successfully develop into a fetus.

What Does It Mean? An Endometrial Receptivity Analysis (or ERA) is a genetic test that may be considered by your physician. It takes a small sample of the endometrial lining to determine which day would be the best day to transfer the embryo during an IVF cycle.

Performing an ERA can be very helpful since the window of endometrial receptivity can be one of the causes of infertility in women who have had two or more unsuccessful embryo transfers following IVF.