In vitro fertilization (IVF) has transformed the landscape of fertility treatment, offering hope to millions of people who dream of becoming parents. Since the first IVF baby was born in 1978, more than 8 million babies worldwide have entered the world thanks to this technology. Yet for many intended parents, the scientific process behind IVF can seem daunting or mysterious. This article breaks down the steps of IVF and embryo transfer in clear, simple terms. We’ll explain what IVF is, when it’s used, how embryos are created and transferred, and what to expect at each stage. Whether you’re considering IVF for yourself or through a gestational surrogate, this guide will demystify the process and address common questions about success rates, risks, and emotional considerations. By understanding “the science behind the scenes,” you can approach IVF with greater confidence and clarity on your path to parenthood.
A conceptual illustration of the IVF process, where eggs are retrieved from a woman’s ovaries and fertilized with sperm in a laboratory dish. The resulting embryo is then transferred into the uterus (right) to hopefully establish a pregnancy. IVF has enabled millions of people worldwide to have children when natural conception is not possible.
What Is IVF and When Is It Used?
In Vitro Fertilization (IVF) is a form of assisted reproductive technology (ART) in which an egg is fertilized by sperm outside the human body, in a laboratory setting. The term “in vitro” literally means “in glass,” referring to the lab dish (often called a petri dish or test tube) where fertilization occurs. In a successful IVF cycle, doctors retrieve mature eggs from a woman’s ovaries, fertilize them with sperm in the lab to form embryos, and then transfer one of these embryos into the uterus to initiate a pregnancy. If the embryo implants in the uterine lining, it can develop into a baby just as in a natural pregnancy.
When is IVF used? IVF can help overcome a variety of fertility challenges and is used by people who need assistance achieving pregnancy. Originally developed to bypass blocked or damaged fallopian tubes, IVF today is a solution for many situations, including:
Tubal factor infertility: Blocked, scarred, or absent fallopian tubes (which prevent natural fertilization)
Male factor infertility: Low sperm count or poor sperm motility/quality that makes natural conception difficult
Ovulation disorders or ovarian conditions: For example, women with endometriosis, polycystic ovary syndrome (PCOS), or other issues may benefit from IVF
Advanced maternal age: IVF is often recommended for individuals of advanced reproductive age or those with diminished ovarian reserve, as it can improve chances by carefully controlling fertilization and embryo selection
Unexplained infertility: When other methods (like fertility drugs or intrauterine insemination) have not worked, IVF may be the next step
Genetic reasons: Couples at risk of passing on a genetic disease sometimes use IVF with preimplantation genetic testing to select healthy embryos
Family building for LGBTQ+ and single parents: IVF allows same-sex male couples or single men to have a child via gestational surrogacy, and same-sex female couples or single women to combine donor sperm with their own or donor eggs
Gestational surrogacy: If a person cannot carry a pregnancy due to health issues or absence of a uterus, IVF is used to create embryos that a gestational carrier (surrogate) will carry on their behalf. In gestational surrogacy, the surrogate has no genetic link to the child; instead, embryos are created via IVF using the intended parents’ (or donors’) sperm and eggs.
In summary, IVF is a versatile technique used whenever natural conception is not possible or carries particular risks. It has become one of the most effective and common ART methods, with doctors recommending IVF in about 5% of infertility cases. Thanks to IVF, many individuals and couples who once had little hope of having a baby now have a viable path to parenthood.
Step-by-Step: The IVF Process
While IVF involves advanced laboratory science, it follows a series of clear steps. A typical IVF cycle spans several weeks and can be broken down into four main phases: ovarian stimulation, egg retrieval, fertilization & embryo development, and embryo transfer. Below, we walk through each step in order, so you know what happens and why.
1. Ovarian Stimulation
In a natural menstrual cycle, a woman’s ovaries normally mature and release just one egg per month. IVF, however, aims to obtain multiple eggs in one cycle to increase the chances of success. To do this, fertility specialists use hormonal medications to stimulate the ovaries into maturing a whole group of eggs simultaneously.
Fertility medications: You (the egg provider, who may be the intended mother or an egg donor) will take daily hormone injections for about 8–14 days. These typically include follicle-stimulating hormone (FSH) and luteinizing hormone (LH) analogs, which encourage many ovarian follicles to develop at once. Instead of the single egg that would normally mature, the goal is to have several eggs ready for collection. During this period, some providers also prescribe medications like birth control pills or estrogen in advance to synchronize the cycle and prevent ovarian cysts. A medication called a “trigger shot” (often human chorionic gonadotropin, hCG) is given as the final injection to trigger the final maturation of the eggs once they are deemed ready.
Monitoring: Throughout stimulation, you will have frequent monitoring appointments. Doctors use ultrasound scans to check the growth of ovarian follicles (the fluid-filled sacs where each egg grows) and blood tests to measure hormone levels. This ensures the medications are working effectively and helps time the egg retrieval. When ultrasounds show that multiple follicles have reached a mature size (often ~18–22 mm in diameter) and hormone levels (like estrogen) are high enough, the trigger shot is administered. Precisely 36 hours after the trigger injection, the next step — egg retrieval — will take place.
Ovarian stimulation can cause some side effects from high hormone levels (bloating, mood swings, etc.), but it is generally well-tolerated. In rare cases, if the ovaries over-respond, a condition called ovarian hyperstimulation syndrome (OHSS) can occur, causing more severe bloating and discomfort. Fertility clinics carefully adjust medication doses and monitor patients to minimize such risks.
2. Egg Retrieval
Egg retrieval is a minor surgical procedure performed to collect the mature eggs from the ovaries. It is typically done under light sedation or anesthesia to ensure comfort. Here’s how it works:
The doctor, guided by transvaginal ultrasound, inserts a thin needle through the vaginal wall into each ovary. This sounds intense, but you’ll be sedated and it usually takes only about 15–20 minutes.
The needle is used to gently aspirate (suction out) the fluid from each follicle, and with it, the egg. Each ovary may yield several eggs if the stimulation was successful. The fluid containing the eggs is collected into test tubes and immediately handed to the embryologist in the lab.
The embryologist searches the fluid under a microscope to locate all the eggs. Retrieved eggs are placed in a special culture medium (nutrient fluid) in a petri dish and kept warm in an incubator.
After the procedure, you’ll rest briefly and usually go home the same day. Mild cramping or spotting is common, but recovery is quick. Because anesthesia is used, clinics often advise not driving for 24 hours after retrieval. Most people feel back to normal by the next day.
On the same day as egg retrieval, a sperm sample is prepared. If using a partner’s sperm, he will provide a sample (typically via masturbation) that morning. If donor sperm is being used, it will be thawed from frozen storage. The lab will wash and concentrate the sperm, selecting the healthiest, most active sperm cells for fertilization. Timing is critical: eggs and sperm are brought together in the lab within hours of the retrieval.
3. Fertilization and Embryo Development
Once we have eggs and prepared sperm, the next step is to create embryos in the lab. Fertilization can be performed in one of two main ways:
Conventional IVF insemination: The eggs are placed in a petri dish with thousands of sperm cells and left overnight. Fertilization occurs “naturally” as one sperm penetrates each egg on its own (if all goes well).
ICSI (Intracytoplasmic Sperm Injection): A specialized procedure often used in IVF, especially for male factor infertility. An embryologist will select a single sperm and inject it directly into the cytoplasm of each egg using a fine needle. ICSI bypasses many sperm-related issues and can improve fertilization rates when sperm count or motility is low. Many clinics use ICSI for all or most IVF cases nowadays to maximize fertilization chances.
By the next day (often called “Day 1” in the lab), the team checks how many eggs have fertilized normally. A normally fertilized egg becomes a one-cell embryo called a zygote, identifiable by the presence of two pronuclei (one from the egg, one from the sperm) when viewed under a microscope. Typically, not every egg will fertilize; an average might be around 70% of mature eggs successfully fertilized. For example, if 10 eggs were retrieved and were mature, perhaps 6–8 may fertilize and start developing.
Embryo development: The fertilized eggs (now embryos) are kept in incubators that mimic the conditions of the human body. Over the next 5–6 days, they will divide and grow, ideally reaching the blastocyst stage. A blastocyst (usually formed on Day 5 after fertilization) is an embryo of around 100–150 cells that has begun to differentiate into two cell types (an inner cell mass that will form the fetus, and an outer layer that will form the placenta). Not all embryos make it this far; in fact, usually only about 40–50% of fertilized embryos progress to a healthy blastocyst. (For instance, if 6 embryos were growing on Day 1, you might end up with 2 or 3 good blastocysts by Day 5.) This attrition is normal – it’s nature’s way of selecting the hardiest embryos.
During the culture period, embryologists monitor the embryos’ cell division under the microscope. They may grade embryo quality based on appearance and growth rate. If there are concerns by Day 3 (when embryos are around 6–8 cells), sometimes an early transfer on Day 3 is considered, but many clinics prefer to grow to Day 5 if possible, as blastocysts have higher implantation potential. In some cases, preimplantation genetic testing (PGT) is done at this stage (typically on Day 5 blastocysts) to screen embryos for chromosomal abnormalities or specific genetic diseases. If PGT is planned, the embryos are biopsied and then usually frozen while awaiting results.
By the end of the first week, we ideally have one or more viable embryos ready to transfer or freeze. The next step is to place one of those embryos into the uterus – the embryo transfer.
4. Embryo Transfer
The embryo transfer is the final step of the IVF process and the moment everyone has been waiting for: introducing the embryo into the prospective mother’s (or surrogate’s) uterus in hopes that it will implant and lead to a pregnancy. The procedure is relatively quick and painless, usually requiring no anesthesia. Here’s what to expect:
The transfer typically occurs either 3 days or 5 days after egg retrieval if it’s a fresh transfer (more on “fresh vs frozen” below). If embryos have been frozen from a previous cycle, the transfer is scheduled according to a prepared timeline.
Before the procedure, the doctor will confirm how many embryos will be transferred (in most cases one, or sometimes two). This decision is based on factors like embryo quality, patient age, and prior history. Transferring a single embryo is now standard in many cases to avoid the risks of twins or multiples, though older patients or those with repeated failures might transfer two embryos to improve odds.
The actual transfer is done with a thin, flexible catheter (tube). You will lie on a exam table as you would for a pelvic exam. A speculum is inserted into the vagina, and the doctor visualizes the cervix. The embryo(s), suspended in a tiny drop of fluid, are drawn into the catheter, which is gently threaded through the cervix into the uterine cavity. Using ultrasound guidance, the doctor positions the catheter at the ideal spot and releases the embryo into the uterus.
The procedure only takes about 5-10 minutes, and aside from mild discomfort from the speculum, it shouldn’t hurt. Patients often liken it to a Pap smear exam. No recovery time is needed – you can go home after a brief rest. The clinic may have you lie down for a short period afterwards, but full bed rest is generally not required; normal light activities can resume the next day.
Importantly, the transferred embryo is microscopic – you won’t feel it being released. After transfer, the embryologist will check the catheter under a microscope to ensure the embryo didn’t stick inside (a routine step). Now the waiting begins: about 9-14 days later, a blood test will check if pregnancy has been achieved. This “two-week wait” can be an emotional time as you hope for positive news.
If extra embryos were created beyond the one transferred, those remaining embryos can be frozen for future use (this is very common). Frozen embryos give additional chances at pregnancy without having to repeat the entire IVF stimulation and egg retrieval process again.
Fresh vs. Frozen Embryo Transfers
You may have heard about fresh versus frozen embryo transfers in IVF. The difference is straightforward, but it can have practical and even outcome implications:
Fresh Embryo Transfer: This means the embryo is transferred in the same cycle it was created, just a few days after the egg retrieval. For example, if eggs were retrieved on Monday, a fresh transfer might occur on Thursday or Saturday of that week (day 3 or day 5 embryo). The embryo goes directly from the lab into the patient’s uterus without ever being frozen.
Frozen Embryo Transfer (FET): In this case, the embryos are cryopreserved (frozen) after they reach the blastocyst stage, and stored in liquid nitrogen. The transfer happens at a later date – sometimes the very next month, or sometimes years later depending on the situation. When the patient is ready for a pregnancy attempt, an embryo is thawed and transferred into the uterus.
Both fresh and frozen transfers use the same procedure for placing the embryo in the uterus; the only difference is whether the embryo was frozen beforehand. Why would a clinic choose one over the other? There are several considerations:
Scheduling and convenience: Frozen transfers offer more flexibility. The timing can be planned optimally for the patient and clinic. With fresh transfers, everything is tied to the stimulation cycle’s timeline.
Uterine readiness: In a fresh transfer, the woman’s body has just undergone ovarian stimulation, which can affect hormone levels and uterine lining receptivity. Some doctors prefer to freeze all embryos and do a transfer in a later, more natural cycle or a hormonally prepared cycle, believing the uterus may be more receptive then (since it isn’t hyper-stimulated).
Success rates: Modern freezing techniques (vitrification) are very advanced, and frozen embryo transfers have become extremely successful. In fact, many clinics report equal or even higher success rates with FETs compared to fresh transfers. One reason is that only the best embryos are frozen, and the timing can be optimized. Research has shown that for certain patients, FET can lead to higher pregnancy rates and a lower risk of complications like OHSS.
When fresh is necessary: In some cases, a fresh transfer is still preferred or necessary – for instance, if there is a pressing reason to attempt pregnancy immediately, or if the patient did not produce many embryos and is ready to transfer one right away. Fresh transfers also avoid the cost of freezing. However, if a patient shows signs of OHSS or other issues, doctors will cancel a fresh transfer and freeze the embryos for later, to protect the patient’s health.
In summary, a fresh transfer is immediate, while a frozen transfer involves an additional step of freezing/thawing. Both approaches can be very effective. Your doctor will recommend what’s best based on your specific medical situation. Many IVF journeys nowadays involve creating embryos, freezing them, and transferring in a subsequent cycle as a standard practice, often referred to as a “freeze-all” approach.
IVF and Surrogacy: Using Gestational Carriers
IVF plays a crucial role in gestational surrogacy (also called gestational carrier arrangements). In gestational surrogacy, another woman (the surrogate) carries a pregnancy for the intended parent(s), but she is not the genetic mother of the child. How is that possible? Through IVF.
In a surrogacy arrangement, IVF is used to create embryos using the gametes (sperm and eggs) from the intended parents or donors. For example, an intended mother may undergo ovarian stimulation and egg retrieval, and an intended father provides sperm, allowing the IVF lab to create embryos that are genetically related to the intended parents. If the intended mother cannot provide eggs, an egg donor would be used; if the intended father cannot provide sperm, a sperm donor can be used. What’s important is that the surrogate’s own eggs are not involved – she’s truly a carrier and not biologically related to the baby.
Once embryos exist, one (or more) of them is transferred into the surrogate’s uterus in a procedure exactly like a regular embryo transfer. The surrogate’s medical cycle is coordinated accordingly: she may take hormones (estrogen and progesterone) to prepare her uterine lining to be receptive at the time of transfer, especially if the embryos are frozen and the transfer timing is planned. In many surrogacy cases, all embryos are created and frozen first, then the best embryo is selected for transfer to the surrogate.
The step-by-step in surrogacy basically mirrors a standard IVF cycle, except that the roles are split between different people: one person (intended mother or egg donor) goes through ovarian stimulation and egg retrieval, and another person (the surrogate) undergoes the embryo transfer and carries the pregnancy. Legal agreements are in place before any of this begins, because surrogacy involves additional considerations beyond medical ones. But scientifically speaking, gestational surrogacy would not be possible without IVF – it’s the technology that allows the creation of an embryo in a lab so it can be implanted in another woman’s uterus.
Intended parents considering surrogacy should understand that IVF is a key part of the process. This means the journey will involve fertility clinic procedures not just for the surrogate, but potentially for the intended mother or an egg donor. Success rates for surrogacy largely depend on the quality of the embryos created via IVF and the reproductive health of the surrogate. The good news is that surrogacy using IVF (with a healthy surrogate and good embryos) has very high success rates, often on the first or second transfer, because the typical obstacles to pregnancy (like unhealthy uterus or eggs) are mitigated by carefully selecting both the embryo and the carrier.
Common Concerns About IVF
It’s normal to have lots of questions and concerns when considering IVF. Beyond the basic “how it works,” intended parents often worry about how successful the procedure is, what risks are involved, and how many embryos should be transferred for the best outcome. We address some of these common concerns below:
Success Rates
One of the first questions people ask is, “What are the chances that IVF will work?” The success rate of IVF depends on many factors, especially the age of the woman providing the eggs (either the patient or an egg donor). Younger eggs generally yield higher success due to better egg quality. For example, women under 35 have around a 40-50% chance of a live birth per IVF cycle, whereas a woman in her early 40s might have only a 5-10% chance per cycle with her own eggs. These percentages are averages; individual clinics may have slightly different rates, and using donor eggs (often from a younger woman) can significantly boost success for older recipients.
It’s important to discuss your personal prognosis with your doctor. They will evaluate factors such as your ovarian reserve (egg supply), sperm parameters, uterine health, and any prior pregnancy history. Sometimes multiple IVF cycles are needed to achieve a pregnancy. While one couple may be lucky on the first try, another might require two, three, or more attempts. Cumulative success rates (the chance of success over 2-3 cycles) are higher, so even if the first transfer fails, trying again often leads to a successful outcome. Overall, IVF is one of the most effective fertility treatments available, and millions of babies born through IVF are testament to its success.
Risks and Side Effects
IVF is generally safe, but like any medical procedure it comes with some risks and side effects. Here are a few to be aware of:
Multiple pregnancy: If more than one embryo is transferred, there is a risk of twins or higher-order multiples. A multiple pregnancy carries higher chances of complications for both mother and babies, including premature birth. To minimize this risk, fertility specialists today often recommend transferring a single embryo (especially for younger patients with high-quality embryos) – this approach is called SET (single embryo transfer).
Medication side effects: The fertility drugs used for ovarian stimulation can cause temporary side effects like bloating, headaches, mood swings, and abdominal discomfort. In rare cases, as mentioned, Ovarian Hyperstimulation Syndrome (OHSS) can occur, causing more severe symptoms that might require treatment. Clinics monitor patients closely to catch early signs of OHSS.
Egg retrieval procedure: The egg retrieval is minor surgery, but there are small risks of bleeding, infection, or injury to surrounding organs during the procedure. Serious complications are uncommon since the procedure is done under ultrasound guidance.
Ectopic pregnancy: A very small percentage of IVF pregnancies can implant in the wrong place (like the fallopian tube), leading to an ectopic pregnancy. This is one reason early monitoring with ultrasound is important after a positive test.
Miscarriage: Unfortunately, not every embryo that implants will result in a baby. Miscarriage rates in IVF roughly mirror natural rates and are largely related to the age of the eggs and genetic health of the embryo. IVF doesn’t eliminate the chance of miscarriage, but techniques like PGT can help reduce the risk by selecting chromosomally normal embryos.
It’s worth noting that IVF itself does not appear to cause long-term health issues in women; studies have not shown an increased overall risk of things like cancer due to IVF hormone use. Babies born via IVF are generally as healthy as other babies, though some studies have observed a slightly higher incidence of certain birth defects – likely related to the parents’ underlying infertility factors rather than the IVF process itself. As always, it’s important to discuss all these risks with your doctor, who can provide perspective based on the latest research and your personal situation.
Number of Embryos to Transfer
Deciding how many embryos to transfer is a common dilemma in IVF. On one hand, transferring more than one at a time can increase the immediate chance of any pregnancy; on the other hand, it also increases the chance of twins or multiples, which carry higher risks. The trend in modern IVF is toward elective Single Embryo Transfer (eSET) in most cases, especially for younger patients and when high-quality blastocysts are available. By transferring one embryo at a time, the aim is to achieve a healthy singleton pregnancy and avoid the complications of multiples. If the first embryo doesn’t implant, there are usually frozen embryos available to try again.
For some patients, particularly those of advanced age or with previous IVF failures, doctors might consider transferring two embryos to maximize the odds of success. Transferring more than two embryos at once is now very uncommon and usually discouraged except in special circumstances, because the risk of triplets or higher-order multiples becomes too high. Fertility clinics must follow guidelines (such as those from professional societies or government regulations) on the recommended number of embryos to transfer based on patient age, embryo stage, and other factors. Always have a frank discussion with your IVF team: they will recommend an approach tailored to balancing success rates with safety. Remember, even twins are a high-risk pregnancy for the mother and babies, so the goal is one healthy baby at a time.
Emotional and Practical Considerations
While IVF is a medical process, it’s also a profound emotional journey for the intended parents. Understanding the emotional and practical aspects can help you prepare:
Emotional highs and lows: It’s normal to feel a rollercoaster of emotions during IVF – hope, anxiety, excitement, and sometimes disappointment. The waiting periods (for follicles to grow, for fertilization results, for the pregnancy test) can be stressful. Many people undergoing IVF report heightened anxiety and even symptoms of depression. It’s important to take care of your mental health during this time. Lean on your support network – whether that’s your partner, family, friends, a support group of others going through infertility, or a professional counselor. Clinics often have resources like fertility counselors who understand what you’re going through. Don’t hesitate to seek support; emotional well-being is an important part of the journey.
Physical demands: IVF involves frequent doctor visits, blood draws, ultrasounds, and daily injections for a couple of weeks. This can be tiring and sometimes uncomfortable. Plan your schedule to accommodate these appointments – you might need to go to the clinic early in the morning several times a week. After egg retrieval, you’ll need a day or two to rest and recover from the procedure (bloating and cramping can persist for a short while). During the two-week wait after transfer, every twinge might make you wonder if it’s a pregnancy symptom. It’s a lot for the body and mind, so try to maintain a healthy lifestyle (balanced diet, adequate sleep, gentle exercise if approved by your doctor) to help manage the physical stress.
Practical considerations: Cost is a major practical consideration in IVF. Depending on your country and insurance coverage, IVF can be expensive. It’s wise to understand all the costs up front – not just the main procedure, but medications, monitoring, embryo freezing fees, etc. Some patients may need to budget for more than one cycle if the first attempt is not successful. Additionally, consider the logistics: you might need to travel if your chosen clinic is far, or you might need to arrange time off work especially around the egg retrieval. If you’re doing surrogacy, there are even more logistics and costs (legal, agency fees, surrogate support, etc.), so careful planning is crucial.
Ethical and personal values: IVF can bring up ethical questions or personal values decisions, such as what to do with extra embryos, whether to use genetic testing, or how you feel about the possibility of multiples. Take time to discuss these topics with your partner or advisors so that you’re comfortable with each decision you make. For instance, you might need to decide how many embryos to create or what to do with any remaining frozen embryos once your family is complete.
Resilience and hope: Perhaps the most important consideration is acknowledging that IVF can be unpredictable. Some people are fortunate to succeed on the first try, while others endure multiple cycles. It can be emotionally draining if you encounter setbacks like a failed cycle or a miscarriage. Try to maintain hope and remember why you’re going through this effort. Celebrate the small victories along the way (like a good retrieval or a positive fertilization report). Every step is progress. If things don’t work out immediately, your medical team will learn more about how your body responds and can adjust the approach. Many, many families who stick with fertility treatment do eventually have a baby, whether through IVF, donor options, or surrogacy. Stay focused on the goal, but also be kind to yourself throughout the process.
Conclusion: Moving Forward with Confidence
IVF is a remarkable melding of science and hope – a process that has allowed countless families to overcome infertility and welcome a child into their lives. By understanding the fundamentals of IVF and embryo transfer, you’ve taken an important step in empowering yourself on this journey. We’ve covered what IVF is, when it’s used, and walked through each stage from ovarian stimulation to embryo transfer. We’ve also discussed fresh vs. frozen embryos, how IVF enables gestational surrogacy, and addressed common concerns and emotions that come with the territory.
Armed with this knowledge, you can approach IVF with clearer expectations and less fear of the unknown. Every patient’s situation is unique, so the next best step is to get personalized advice from a fertility specialist. If you’re considering IVF or surrogacy as an intended parent, we encourage you to reach out for a consultation with our clinic’s experienced team. We are here to answer your questions, discuss your options, and support you through every step of the process. Making the decision to pursue IVF is big, but you don’t have to navigate it alone – our doctors, nurses, and counselors will partner with you to maximize your chances of success in a compassionate, professional environment.
Call to Action: Contact us today to schedule an appointment or to learn more about our IVF and surrogacy programs. The journey might seem complex, but with the right knowledge and the right support, you can move forward confidently toward the family you’ve been dreaming of. We are dedicated to helping you realize that dream through the science and art of IVF.