Picture of Esther H. Chung
Esther H. Chung
MD, Duke University
Kelly Acharya
MD, Duke University

The Basics of In Vitro Fertilization (IVF) and Intracytoplasmic Sperm Injection (ICSI)

If you want to learn more about In-Vitro Fertilization (IVF) and Intracytoplasmic sperm injection (ICSI), this article is a good place to start. Read on to get the basic knowledge about IVF and ICSI.

In-Vitro Fertilization (IVF) is becoming more and more common around the world. For example, in the United States, about 2% of all births result from IVF. Generally speaking, IVF is the process of collecting a woman’s oocytes (eggs) and a man’s sperm, and then combining these outside of the body to create fertilized eggs, or embryos.

There are various medication protocols your doctor may recommend for your IVF cycle; however, the basic steps are fairly standard. Though the IVF process can be daunting for many, both financially and personally, we will try to break down the process. Very likely you will also have an IVF nurse who can help you along each step of the process and answer questions throughout your IVF cycle. Here’s what you can expect through the IVF process.

If you want to learn more about the different types of IVF protocol, follow the link to read more.

Ovarian stimulation

During this part of the process, the woman will take daily hormones via injections in order to stimulate her ovaries to produce multiple eggs. The dose of hormonal medication may vary, depending on a particular clinic and each cycle. During this process, the ovarian “follicles” (fluid-filled cysts containing the eggs) are typically measured regularly by transvaginal ultrasound, and hormone testing is performed (blood draw). During this phase, she will be in regular contact with her fertility team, who may adjust her medications. It is important that she understand these changes and ask as many questions as needed, to make sure she is taking the proper dose.

Sometimes, a woman may skip the step of taking hormones that stimulate her ovaries. This is called a natural-cycle IVF.

Woman taking an injection during IVF treatment

HCG trigger shot

When one or more ovarian follicles have grown large enough to contain a mature egg, the team will decide it is time to give an injection of human chorionic gonadotropic (hCG) which will be given to mature the eggs in preparation for retrieval. The woman will then be instructed to return to the clinic about 36 hours to have the eggs retrieved from the ovaries.

Egg retrieval

When the follicles appear ready and trigger shot has been given, the egg retrieval is performed. In this procedure, a probe is placed into the vagina so the provider can see the ovaries on the ultrasound screen (scan). Once the ovary is in view, a very thin needle is inserted through the vaginal wall and into each ovarian follicle to aspirate (suction) the eggs. Egg retrieval typically happens in a doctor’s office or a clinic about 36 hours after the “trigger shot”. During the retrieval process, the woman will typically be sedated (sleepy) or asleep with medication. 

After the procedure, the woman will be observed for an hour or two and given medication for any pain. After that, she can go home to rest.

Woman having an ultrasound scan before egg retrieval as a part of an IVF procedure


There are two common methods to fertilize the retrieved eggs in the laboratory. It is worth mentioning that usually not all the eggs fertilize normally, so the number of embryos produced is less than the number of eggs retrieved. The reasons for the failure of the eggs to fertilize can include problems with the eggs themselves, or with the sperm that is being used to fertilize them.

  1. Conventional insemination (IVF) – the process of mixing sperm and eggs in an incubator overnight without further laboratory manipulation or intervention. If you want to read more about IVF treatment with donor sperm, then follow the link.
  2. Intracytoplasmic sperm injection (ICSI) – the process of injecting a single sperm, selected by an embryologist on the basis of its quality, directly into each mature egg. ICSI is often used when semen quality is a problem, or after IVF cycles done with conventional insemination have failed. The sperms for injection are selected in the laboratory by a scientist by (an embryologist). This is because in situations where sperm quality is a problem, the chance of the egg being successfully fertilized by the egg through IVF is low. ICSI overcomes this problem, but overall, in properly selected patients, the chance of having a baby by IVF or by ICSI is no different. If you want to read more about ICSI treatment with donor sperm, then follow the link.

Embryo Transfer

The embryo transferred is a fertilized egg that has been kept in specially controlled conditions in the IVF lab for 2 to 6 days. The decision to proceed with a fresh transfer that day, or to freeze the embryos to be transferred at a later time depends on the woman’s unique situation and this is something that the clinic will discuss with the women, if they feel that freezing all the embryos will be beneficial.
  1. Fresh embryo transfer: A fresh transfer involves transferring an embryo in the same cycle in which the ovaries were stimulated, and the eggs were retrieved.
  2. Frozen Embryo Transfer (FET): Often, embryos can be frozen 3-5 days after the egg retrieval and can then be transferred in a later cycle. FET cycles may involve monitoring a woman’s natural cycle to determine the optimal time for embryo transfer versus giving hormonal therapies to prepare the uterus for transfer. (please see article on oocyte and embryo storage)

Once the embryo(s) has been selected for transfer into the womb, a syringe and very thin catheter is inserted through the cervix (entrance of the womb) into the uterus to place one or more embryos directly into the womb. This is typically under ultrasound guidance. This is generally a painless procedure, although the woman may experience mild cramping.

After the Transfer

About 1.5-2 weeks after the embryo transfer, the clinic will test a sample of the woman’s blood to determine if she is pregnant.

  1. During that initial waiting time, she can typically resume normal daily activities, although some clinics and physicians recommend avoidance of strenuous activity.
  2. Women often are advised to continue hormone supplementation (for example, with estrogen and/or progestins) after the egg retrieval.
  3. If pregnant, the woman will typically undergo an ultrasound about 4-5 weeks after the embryo transfer (6-7 weeks of gestation) to further monitor the pregnancy.

My team is advising me to transfer one embryo, even though we have many healthy ones. Why?

There is an international effort to increase single embryo transfer (SET), or transfer of only one embryo rather than multiple embryos at once; this helps to avoid the many risks of multiple pregnancy (twins, triplets, or more). The ultimate goal of an IVF cycle is a single, healthy, live baby.

What happens where there are left over embryos after an IVF cycle?

Sometimes, there are excess embryos that can be cryopreserved (frozen) for your later use. At that point, you may be able to undergo a subsequent frozen embryo transfer to attempt a pregnancy with those embryo(s). Sometimes and only with your written consent, the embryos can be donated to other couples affected by fertility problems; or may be used for research projects or for training embryologists. The clinic may discuss this with you.

A doctor explaining the chances of success with IVF or ICSI treatment

What are my chances that IVF/ICSI will work?

The chances of giving birth to a healthy baby through IVF depend on a few key factors, including maternal age, reproductive history, genetics, and prior medical history, among others.

IVF/ICSI is generally considered the most effective form of assisted reproductive technology (ART) with the highest per-month chance of success. However, results can vary significantly for different patients based on age and the underlying infertility diagnosis. The effectiveness of an IVF cycle is also gauged by the outcomes of your prior IVF cycles. Every IVF cycle yields highly individualized information about how your body will respond to the particular stimulation protocol. You can ask your clinic what their success rates are, or look at national websites that report success rates of clinics such as SART or HFEA.

Are there risks with IVF?

The main risks include an over response to ovarian stimulation (ovarian hyperstimulation syndrome-OHSS) and complications in both the pregnancy and to children conceived that are of multiple gestation pregnancies (twins, triplets, etc.). There is also a small increase in the general risks of pregnancy risks such as hypertensive disorders of pregnancy (pre-eclampsia) or preterm labor.

Overall, though, IVF/ICSI is generally considered a safe and effective treatment that can help give a chance at pregnancy to patients who otherwise would not have been able to conceive. Please consult your doctor to understand your personal chances and risk factors when undergoing IVF (with or without ICSI) for infertility treatment. You can read more about the risks of fertility treatment in this article.