What's the difference between IUI and IVF? A guide to the language of assisted conception.

No one ever plans to struggle with infertility. But, for those having trouble conceiving, it's a good idea to talk to a doctor about next steps. That may include undergoing assisted reproductive technology (ART), which spans a huge range from taking medication to stimulate ovulation to undergoing IVF — and that's where things can get confusing.

"Learning all the new words and acronyms associated with fertility treatment can feel like learning a new language," Dr. Jenna Turocy, a reproductive endocrinologist at the Columbia University Fertility Center, tells Yahoo Life. While they may have some baseline knowledge of things like IVF, many people don't "fully understand the process until they are about to experience it," Dr. James Grifo, director of the NYU Langone Fertility Center, adds.

Sure, a good doctor should explain things in terms that are easy to understand, but it can also be helpful to learn the lingo, reproductive endocrinologist Dr. Asima Ahmad, chief medical officer and co-founder of Carrot Fertility, tells Yahoo Life. "This allows you to spend less time understanding what the words mean and more time being able to ask questions you might have about the ART process or outcomes," she explains.

It can also help patients to do their own research and to connect with others going through a similar process, Dr. Jane Frederick, a board-certified reproductive endocrinologist at HRC Fertility, says. "It's helpful when we're all using the same terms," she says.

Doctors say these are some of the important big terms to know.

AMH

AMH stands for Anti-Müllerian hormone, which is made by the ovarian follicle that contains an egg. "This is a hormone that is measured as a marker of ovarian reserve," Ahmad says. (Ovarian reserve, as explained later, is essentially how many eggs a woman has.)

Blastocyst

A blastocyst is an embryo that has been developed to day five or six of development. It contains rapidly dividing cells that develop into the fetus and trophectoderm cells that will become the placenta.

Clomid

Clomid is the brand name for clomiphene, an estrogen modulator and oral medication that's frequently used to stimulate the ovaries. Clomid if often used in the case of an intrauterine insemination (IUI).

Donor egg

If doctors are unable to retrieve a patient's eggs, those eggs are not considered the right quality to produce a viable embryo or the patient is part of a couple in which one person doesn't produce eggs, a doctor may recommend that using a donor egg. This is an egg that comes from another person.

Egg

Also known as an oocyte, "an egg is a single cell that's very fragile," Frederick says.

Egg freezing

Egg freezing is the process of harvesting and preserving a woman's eggs for future use. These eggs may later be used to make an embryo. "More women are asking what their reproductive options are for the future, and the best chance of preserving their fertility is through egg freezing," Grifo says.

Embryo

An embryo is a fertilized egg that typically contains 100 cells. "It is much more sturdy in terms of tissue, compared to an egg," Frederick says. "It can withstand the freezing and storage process more than an egg."

Embryo transfer

Embryo transfer is the process of taking eggs that have been fertilized with sperm and implanting them in a woman's womb.

Follicle

A follicle is a small fluid-filled sac that surrounds an egg. "These can measure 2 to 9 millimeters in size," Ahmad says.

FSH

FSH stands for follicle-stimulating hormone (FSH), a hormone linked with the development of eggs in women and sperm in men. FSH levels in women change during menstrual cycle, with the highest levels happening just before ovulation (when an egg is released by the ovary).

Gametes

Gametes are reproductive cells and can be used to describe an egg or sperm.

Gestational surrogate

A gestational surrogate is someone who carries a pregnancy for a person or couple. They may be used in the case of same-sex couples or when someone is unable or unwilling to carry a pregnancy themselves.

Gonadotrophins

These are hormones that are given to stimulate the ovaries to create eggs as part of assisted conception. They are given by injection and include follicle stimulating hormone (FSH) and luteinizing hormone (LH).

hCG

HCG stands for Human Chorionic Gonadotrophin, a hormone that helps eggs mature. If a patient is undergoing an egg retrieval, they'll typically get an hCG injection to help their eggs mature for collection.

ICSI

ICSI (intracytoplasmic sperm injection) is a procedure that involves injecting sperm into a patient's eggs in a lab with the goal of creating a fertilized egg, Frederick says. It's a form of IVF and it's often used when male infertility is a factor.

IUI

IUI is short for intrauterine insemination, a procedure where a doctor takes a small catheter to place sperm inside the uterus during ovulation. "This reduces the distance the sperm has to travel and increases the chances for fertilization," Grifo says.

IVF

IVF is an acronym for in vitro fertilization. "This refers to fertilizing an egg and sperm 'in vitro' or in the lab," Turocy says. IVF includes the process of ovarian stimulation, followed by harvesting eggs, combining them with sperm in the lab, growing them five days in the lab and sometimes testing them before freezing them, Grifo says. "Embryos can be thawed or transferred fresh into the uterus," he says. "This treatment can be used with fresh or frozen egg, sperm or embryo."

LH

LH stands for luteinizing hormone, a chemical that sparks ovulation and helps with the hormone production needed to support pregnancy.

Ovarian reserve

Women are born with a certain number of eggs, and ovarian reserve is a term used to describe how many she has left. "Each female has a different amount of eggs, or ovarian reserve, and this number goes down over time," Ahmad says.

PGT

Preimplantation Genetic Testing (PGT), is a test that screens embryos for potential genetic abnormalities or chromosomal conditions before implantation. "This advanced science is giving people even greater chances of bringing home a healthy baby," Grifo says, noting that it "significantly reduces the incidence of miscarriage."

Single embryo transfer

Many assume that IVF will lead to twins, "but that shouldn't be their goal or that of their doctor because of the risks of a multiple pregnancy." Instead, many doctors will transfer one embryo at a time to try to create a healthy baby.

Again, there are a lot of terms associated with assisted reproduction and it's understandable for those considering fertility treatments to have questions along the way. Patients shouldn't hesitate to ask a doctor they you have questions or concerns, Frederick says. "That's what we're there for," she says.

This article was originally published on April 23, 2023 and has been updated.