IVF Treatment: How In Vitro Fertilization Works

What Is IVF and How Does It Work?

IVF (In Vitro Fertilization) is an assisted reproductive technology where eggs are surgically retrieved from the ovaries, fertilized with sperm in a laboratory dish, and the resulting embryo is transferred to the uterus. The term "in vitro" means "in glass," referring to the laboratory fertilization process.

In vitro fertilization represents one of the most significant advances in reproductive medicine, offering hope to millions of couples struggling with infertility. The procedure bypasses many natural barriers to conception by bringing eggs and sperm together in controlled laboratory conditions, where fertilization can be monitored and optimized.

During a normal conception, an egg is released from the ovary during ovulation, travels through the fallopian tube, and may be fertilized by sperm. The fertilized egg (embryo) then travels to the uterus and implants in the uterine lining. IVF essentially replicates this process outside the body, allowing fertility specialists to overcome various obstacles that may prevent natural conception.

The development of IVF began in the 1970s, with the first successful IVF birth (Louise Brown) occurring in 1978 in England. Since then, over 10 million babies have been born worldwide through IVF and related assisted reproductive technologies. The procedure has become increasingly refined, with improved success rates and reduced risks compared to early techniques.

IVF involves several key stages: ovarian stimulation to produce multiple eggs, egg retrieval, fertilization in the laboratory, embryo culture, and embryo transfer. Each stage is carefully timed and monitored to maximize the chances of a successful pregnancy. The entire process typically takes 4-6 weeks from the start of ovarian stimulation to embryo transfer.

How IVF differs from other fertility treatments

IVF differs from simpler fertility treatments in its complexity and effectiveness. Unlike ovulation induction or intrauterine insemination (IUI), which work within the body's natural reproductive system, IVF removes eggs from the body entirely for fertilization. This allows specialists to confirm fertilization has occurred, select the healthiest embryos for transfer, and bypass blocked or damaged fallopian tubes.

While treatments like IUI place washed sperm directly into the uterus (requiring functional fallopian tubes), IVF completely bypasses the fallopian tubes. This makes IVF the only option for women with blocked or absent tubes, and often the most effective treatment for severe male factor infertility, advanced maternal age, or unexplained infertility that hasn't responded to other treatments.

When Is IVF Recommended?

IVF is recommended when simpler fertility treatments have failed, for blocked or damaged fallopian tubes, severe male factor infertility, endometriosis, unexplained infertility, genetic testing needs, or when using donated eggs or sperm. It may be first-line treatment for women over 40.

The decision to proceed with IVF is made after careful evaluation of both partners and consideration of simpler treatment options. While IVF is highly effective, it is also more invasive and expensive than other fertility treatments, so it's typically recommended when other approaches have failed or when specific conditions make IVF the most appropriate first-line treatment.

Understanding when IVF is the right choice requires knowledge of the various fertility factors that may be contributing to difficulty conceiving. A thorough fertility evaluation for both partners helps identify these factors and guides treatment decisions. Some couples may benefit from trying simpler treatments first, while others may be advised to proceed directly to IVF.

Conditions where IVF is often recommended

Blocked or damaged fallopian tubes: When the fallopian tubes are blocked, scarred, or absent (due to previous surgery, ectopic pregnancy, or congenital absence), eggs cannot travel from the ovaries to the uterus naturally. IVF bypasses the fallopian tubes entirely, making it the only fertility treatment option for these women.

Severe male factor infertility: When sperm count is very low, sperm motility (movement) is poor, or sperm morphology (shape) is abnormal, natural conception becomes difficult or impossible. IVF with ICSI (intracytoplasmic sperm injection) can achieve fertilization with even a single healthy sperm per egg, making parenthood possible for men with severe sperm abnormalities.

Endometriosis: This condition, where tissue similar to the uterine lining grows outside the uterus, can affect fertility through various mechanisms including inflammation, adhesions, and ovarian cysts. Women with moderate to severe endometriosis often have better success with IVF than with other treatments.

Ovulation disorders: While some ovulation problems respond to medications alone, conditions like polycystic ovary syndrome (PCOS) that don't respond to ovulation induction medications may require IVF. Women who produce too few eggs or who have diminished ovarian reserve may also benefit from IVF.

Unexplained infertility: When standard testing doesn't reveal a clear cause for infertility, IVF may be recommended after simpler treatments have failed. IVF allows confirmation that fertilization can occur and provides more control over the reproductive process.

Genetic conditions: Couples carrying genetic conditions may choose IVF with preimplantation genetic testing (PGT) to select embryos without the genetic abnormality. This allows affected couples to have biological children without passing on serious genetic diseases.

Using donated eggs, sperm, or embryos: IVF is necessary when using donated reproductive materials to help those who cannot produce their own eggs or sperm, or for same-sex couples and single individuals building families.

How Do You Prepare for IVF Treatment?

IVF preparation involves comprehensive testing for both partners including hormone blood tests, ultrasound examination, semen analysis, and infectious disease screening. Both partners should optimize health by avoiding smoking and alcohol, maintaining healthy weight, and taking recommended supplements.

Proper preparation for IVF is essential for optimizing success rates and identifying any potential issues before treatment begins. The preparation phase typically takes several weeks and involves both diagnostic testing and lifestyle modifications. Your fertility clinic will guide you through this process with a personalized preparation plan.

The goal of pre-IVF testing is to assess ovarian reserve (the quantity and quality of remaining eggs), evaluate the uterine cavity for any abnormalities that might affect implantation, confirm that no active infections are present, and for male partners, thoroughly evaluate sperm quality. These tests help your fertility team design the most appropriate treatment protocol for your specific situation.

Testing required before IVF

Ovarian reserve testing: Blood tests measuring anti-Mullerian hormone (AMH), follicle-stimulating hormone (FSH), and estradiol levels help predict how the ovaries will respond to stimulation medications. An antral follicle count (AFC) via ultrasound counts the small follicles visible in each ovary at the beginning of the menstrual cycle. These tests help determine medication dosing and set realistic expectations for egg retrieval.

Uterine evaluation: A saline sonohysterogram (SIS) or hysterosalpingogram (HSG) evaluates the uterine cavity for polyps, fibroids, or adhesions that could interfere with embryo implantation. Some clinics perform a mock embryo transfer to map the uterine cavity and ensure smooth transfer during the actual procedure.

Infectious disease screening: Both partners are tested for HIV, hepatitis B, hepatitis C, and sexually transmitted infections before treatment. Any active infections must be treated before proceeding with IVF. This protects both partners, laboratory staff, and any resulting pregnancy.

Semen analysis: A comprehensive semen analysis evaluates sperm count, motility, morphology, and other parameters. If significant abnormalities are found, additional testing or consultation with a urologist may be recommended. The results help determine whether conventional IVF or ICSI is more appropriate.

Lifestyle modifications for IVF success

Both partners can take steps to optimize their fertility before and during IVF treatment. While these modifications cannot guarantee success, they create the best possible conditions for treatment.

Stop smoking: Smoking significantly reduces IVF success rates and increases the risk of miscarriage. Women who smoke typically need higher doses of stimulation medications and produce fewer eggs. Both partners should quit smoking at least three months before treatment if possible.

Limit alcohol consumption: Heavy alcohol use can impair fertility in both men and women. While occasional moderate drinking may be acceptable before treatment begins, most fertility specialists recommend avoiding alcohol completely during an IVF cycle.

Maintain a healthy weight: Both underweight and overweight conditions can affect fertility and IVF success. Women with BMI outside the normal range (18.5-24.9) may have lower success rates. Your clinic may recommend weight management before treatment for optimal results.

Take prenatal vitamins: Folic acid supplementation (at least 400 mcg daily) is essential for preventing neural tube defects and should begin at least one month before conception. Many clinics recommend a comprehensive prenatal vitamin containing folic acid, vitamin D, and other nutrients.

How Does Ovarian Stimulation Work?

Ovarian stimulation uses daily hormone injections (FSH and LH) for 10-12 days to stimulate multiple egg follicles to develop simultaneously. Regular ultrasound monitoring tracks follicle growth, and when follicles reach optimal size, a trigger shot is given to prepare eggs for retrieval.

During a natural menstrual cycle, the body typically releases just one mature egg per month. For IVF, the goal is to stimulate the ovaries to produce multiple eggs, increasing the chances of successful fertilization and having quality embryos for transfer. This is accomplished through carefully controlled hormone injections.

The stimulation phase is critical to IVF success and requires close monitoring to optimize egg production while minimizing the risk of ovarian hyperstimulation syndrome (OHSS). Your fertility team will adjust medication dosages based on your response, and you'll have frequent monitoring appointments to track follicle development.

Types of stimulation protocols

Antagonist protocol: This is the most commonly used protocol. Stimulation medications (FSH and sometimes LH) begin on day 2-3 of the menstrual cycle. After several days, a GnRH antagonist medication is added to prevent premature ovulation. This protocol typically takes 10-12 days and involves fewer injections than longer protocols.

Long protocol (down-regulation): This protocol begins with medications to suppress the body's natural hormones, putting the ovaries in a "resting" state. Typically, this involves nasal spray or injections for 2-3 weeks before stimulation begins. Once suppression is confirmed (via blood test or ultrasound), stimulation medications are started. While longer, this protocol provides more control over the cycle timing.

Natural or mini-IVF: Some clinics offer minimal stimulation or natural cycle IVF, using lower doses of medications or no stimulation at all. While this produces fewer eggs, it may be appropriate for certain patients and reduces the risk of OHSS. Success rates per cycle are generally lower, but cumulative success over multiple cycles can be comparable with lower medication costs.

Monitoring during stimulation

During stimulation, you'll visit the clinic every 2-3 days for monitoring appointments. These include transvaginal ultrasound to count and measure developing follicles, and blood tests to measure estradiol levels (which rise as follicles develop). Based on these results, your fertility team adjusts medication dosages to optimize your response.

The goal is to develop multiple follicles (ideally 8-15) to an optimal size (typically 17-22mm) while keeping estradiol levels within safe ranges. Too few follicles may result in cycle cancellation, while too many increases OHSS risk. Your medical team carefully balances these factors throughout the stimulation phase.

When follicles reach the appropriate size, you'll receive a "trigger shot" - typically hCG (human chorionic gonadotropin) - which causes final egg maturation. The timing of this injection is precise: egg retrieval is scheduled exactly 34-36 hours after the trigger shot, when eggs have matured but before ovulation occurs naturally.

What Happens During Egg Retrieval?

Egg retrieval is a minor surgical procedure performed under sedation, taking 15-20 minutes. Using ultrasound guidance, a thin needle is passed through the vaginal wall to aspirate fluid from each follicle, collecting the eggs. Most women experience mild cramping afterward and can return to normal activities within 1-2 days.

Egg retrieval (also called oocyte pickup or OPU) is the procedure that marks the transition from the stimulation phase to the laboratory phase of IVF. It's a relatively quick procedure performed in the fertility clinic's procedure room, but it requires careful preparation and timing to ensure optimal egg quality.

The procedure is scheduled precisely 34-36 hours after the trigger shot. This timing is critical - if performed too early, eggs may not have completed maturation; if too late, ovulation may have already occurred and eggs lost. Clinics typically give specific instructions about when to take the trigger shot to ensure correct timing.

Before the procedure

You'll receive specific instructions from your clinic about eating and drinking restrictions before the procedure. Typically, you should not eat or drink anything after midnight the night before. You'll need someone to drive you home after the procedure, as sedation affects your ability to drive safely.

On the day of egg retrieval, arrive at the clinic at your scheduled time. You'll change into a gown and have an IV placed for administering sedation. The anesthesiologist or nurse will administer sedation medications - you'll be drowsy and comfortable but typically not completely asleep. Some clinics use general anesthesia instead.

The retrieval procedure

Once sedation takes effect, the fertility doctor performs a transvaginal ultrasound to visualize the ovaries. A thin needle attached to the ultrasound probe is passed through the vaginal wall into each ovarian follicle. Gentle suction aspirates the follicular fluid, which contains the egg, into collection tubes.

Each follicle is drained individually, and the embryologist immediately examines the fluid under a microscope to locate and identify each egg. Not every follicle contains an egg - typically, about 80% of follicles yield an egg. The procedure takes approximately 15-20 minutes depending on the number of follicles.

After egg retrieval

After the procedure, you'll rest in a recovery area for 1-2 hours while the sedation wears off. Mild cramping and spotting are normal and may continue for a few days. Pain similar to menstrual cramps is common and can usually be managed with over-the-counter pain relievers containing paracetamol (acetaminophen). Avoid ibuprofen and other NSAIDs as they may affect implantation.

Most women can return to normal activities within 1-2 days, though strenuous exercise should be avoided until after embryo transfer. Your clinic will inform you how many eggs were retrieved and will contact you the next day with fertilization results.

How Are Eggs Fertilized in the Laboratory?

On the day of egg retrieval, sperm is collected and prepared, then combined with eggs in laboratory dishes. Conventional IVF allows natural fertilization, while ICSI involves injecting a single sperm directly into each egg. Fertilization is confirmed the next day, and embryos develop for 3-6 days before transfer.

The laboratory phase of IVF is where fertilization occurs and embryos develop. Highly specialized embryologists work in controlled laboratory environments to give eggs and embryos the best possible conditions for development. The laboratory maintains precise temperature, humidity, and air quality to mimic conditions in the human body.

On the same day as egg retrieval, sperm must be collected and prepared. Fresh sperm is preferred, collected through masturbation at the clinic in a private room. If the male partner cannot be present or cannot produce a sample, previously frozen sperm or surgically retrieved sperm can be used. The laboratory processes the sperm to select the healthiest, most motile specimens.

Conventional IVF vs. ICSI

Conventional IVF: In this approach, approximately 50,000-100,000 sperm are placed with each egg in a culture dish. The sperm swim toward the egg and one naturally penetrates the outer layer (zona pellucida) to fertilize it. This mimics natural fertilization but in a controlled environment. Conventional IVF is used when sperm parameters are normal.

ICSI (Intracytoplasmic Sperm Injection): ICSI involves the embryologist selecting a single healthy sperm and injecting it directly into the center (cytoplasm) of each mature egg using a microscopic needle. ICSI is recommended when sperm count or motility is low, when sperm must be surgically retrieved, when using frozen sperm that may have reduced motility, or when previous IVF cycles had poor fertilization.

ICSI success rates are similar to conventional IVF when used for appropriate indications. However, ICSI is more labor-intensive and expensive, so it's typically reserved for cases where it provides a clear benefit. Your fertility team will recommend the most appropriate method based on your specific situation.

Embryo development in the laboratory

Fertilization is assessed approximately 16-18 hours after insemination or ICSI. At this stage, successfully fertilized eggs (now called zygotes) show two pronuclei - one from the egg and one from the sperm - visible under the microscope. Eggs with abnormal fertilization (no pronuclei, one pronucleus, or more than two) are typically discarded.

Over the next several days, embryos are cultured in special incubators that maintain optimal conditions. Embryologists monitor development at key stages:

• Day 1: Fertilization check (2-pronuclei stage)
• Day 2: 2-4 cell embryo
• Day 3: 6-8 cell embryo (cleavage stage)
• Day 5-6: Blastocyst stage (100+ cells with distinct inner cell mass and outer layer)

Some clinics transfer embryos at the cleavage stage (Day 3), while others prefer to culture to the blastocyst stage (Day 5-6). Blastocyst transfer allows better embryo selection but requires embryos to survive longer in culture. Your clinic will recommend the optimal transfer timing based on the number and quality of embryos available.

What Happens During Embryo Transfer?

Embryo transfer is a simple procedure taking about 10 minutes, similar to a Pap smear. The embryologist loads the selected embryo(s) into a thin catheter, which the doctor guides through the cervix into the uterus using ultrasound. No anesthesia is needed. You'll rest briefly before going home.

Embryo transfer is the culmination of the IVF cycle - the moment when embryo(s) are placed into the uterus, where implantation and pregnancy may occur. While the preceding steps involve complex medical procedures and laboratory techniques, the transfer itself is relatively simple and usually painless.

Most clinics now perform single embryo transfer (SET) as standard practice, particularly for younger patients with good-quality embryos. Transferring one embryo significantly reduces the risk of twins or higher-order multiples, which carry increased health risks for both mother and babies. Your fertility team will discuss the recommended number of embryos to transfer based on your age, embryo quality, and previous history.

Before the transfer

You'll be asked to arrive with a comfortably full bladder, which helps visualize the uterus on ultrasound and straightens the angle between the cervix and uterus for easier catheter passage. Follow your clinic's specific instructions about fluid intake before your appointment.

Before the transfer, the embryologist and doctor confirm your identity and match you with your embryos - this is a critical safety step. The embryologist will discuss embryo quality and show you images of the embryo(s) being transferred. Quality is graded based on cell number, symmetry, and fragmentation (for cleavage-stage embryos) or inner cell mass and trophectoderm quality (for blastocysts).

The transfer procedure

You'll lie on an examination table, similar to a gynecological exam. The doctor inserts a speculum to visualize the cervix, then gently cleans the cervix. Using ultrasound guidance (usually abdominal ultrasound with the full bladder helping visualization), the doctor passes a thin, flexible catheter through the cervix and into the uterus.

The embryologist loads the embryo(s) into the catheter in a tiny amount of culture medium. When the catheter tip is positioned correctly (typically at the top third of the uterine cavity), the embryo(s) are gently deposited. The catheter is slowly withdrawn and checked under the microscope to confirm the embryo(s) were successfully transferred.

The entire procedure takes approximately 10 minutes and is generally painless - most women describe it as similar to a Pap smear. No anesthesia is required. Some women may experience mild cramping during or after the procedure.

After the transfer

After the transfer, you'll rest at the clinic for 15-30 minutes before going home. Extended bed rest is not necessary and does not improve success rates - you can resume normal activities, though most clinics recommend avoiding strenuous exercise and sexual intercourse until the pregnancy test.

You'll begin or continue progesterone supplementation (via vaginal suppositories, gel, or injections) to support the uterine lining. This hormone helps maintain the pregnancy until the placenta develops sufficiently to produce its own progesterone, typically around 10-12 weeks of pregnancy.

The two weeks between embryo transfer and pregnancy test (often called the "two-week wait") can be emotionally challenging. Some women experience mild cramping or spotting, which can occur with both successful and unsuccessful cycles - these symptoms are not reliable indicators of outcome.

When Do You Take a Pregnancy Test After IVF?

A blood pregnancy test (beta-hCG) is performed approximately 14 days after embryo transfer. Home pregnancy tests are less reliable. If positive, an ultrasound is scheduled 2-3 weeks later to confirm pregnancy viability and location. If negative, progesterone support is stopped and menstruation typically begins within days.

The pregnancy test represents the moment of truth in an IVF cycle - the answer to whether the treatment has succeeded. While home pregnancy tests are available, fertility clinics use a blood test measuring beta-hCG (human chorionic gonadotropin) because it provides more precise information and can detect pregnancy earlier than urine tests.

The test is scheduled approximately 9-14 days after embryo transfer, depending on whether a Day 3 or Day 5 embryo was transferred. This timing allows enough time for the embryo to implant and for hCG levels to rise to detectable levels. Testing too early may give a false negative result.

Understanding your results

Positive result: A positive beta-hCG indicates pregnancy has occurred. The specific level and how it changes over subsequent tests provides information about pregnancy health. Typically, hCG levels should roughly double every 48-72 hours in early pregnancy. Your clinic may schedule repeat blood tests to confirm appropriate hCG rise.

Negative result: A negative result means the cycle was not successful. While disappointing, it's important to know that IVF success is cumulative - most couples who don't succeed on the first cycle have good chances with subsequent attempts. Your clinic will schedule a follow-up appointment to discuss results and plan next steps.

Low or slowly rising hCG: Sometimes hCG levels are detectable but low or rising slowly. This may indicate an early pregnancy that might not progress (biochemical pregnancy), ectopic pregnancy, or a normal pregnancy that simply implanted later. Close monitoring with repeat blood tests and early ultrasound helps clarify the situation.

First ultrasound after positive test

If the pregnancy test is positive, an ultrasound is typically scheduled for 2-3 weeks later (around 6-7 weeks of pregnancy, counting from the last menstrual period). This ultrasound confirms that the pregnancy is located in the uterus (ruling out ectopic pregnancy), identifies the number of gestational sacs and embryos (important since fertility treatment increases twin risk), and checks for a fetal heartbeat.

Seeing a heartbeat at this stage is very reassuring - once a heartbeat is detected at 6-7 weeks, the chance of ongoing pregnancy is approximately 90-95%. Your fertility clinic will typically continue monitoring until 8-10 weeks of pregnancy, then transfer your care to your regular obstetrician or midwife.

What Are the Success Rates of IVF?

IVF success rates depend primarily on maternal age. For women under 35, live birth rates per cycle are 40-50%. Rates decline to 30-40% (ages 35-37), 20-30% (ages 38-40), and 10-15% (ages 41-42). Cumulative success over multiple cycles is significantly higher.

Understanding IVF success rates requires looking at multiple factors, with maternal age being the most significant. Success rates can be measured in different ways - per cycle, per embryo transfer, or cumulatively over multiple cycles - and each provides different but useful information.

Age-related decline in success reflects the biological reality that egg quality decreases as women age. While IVF can help overcome many fertility barriers, it cannot reverse the effects of aging on egg quality. This is why fertility specialists often recommend not delaying treatment for women in their late 30s and 40s.

Other factors affecting success

While age is the primary factor, several other variables influence IVF success rates:

Cause of infertility: Some conditions respond better to IVF than others. Tubal factor infertility often has excellent IVF success rates, while diminished ovarian reserve or poor embryo quality present greater challenges.

Embryo quality: Higher-quality embryos have better implantation rates. Grading systems assess embryo development, and blastocyst-stage embryos generally have higher implantation rates than cleavage-stage embryos.

Previous pregnancies: Women who have previously been pregnant (even without live birth) often have higher success rates than those who have never been pregnant.

Lifestyle factors: Smoking significantly reduces success rates. Obesity and underweight conditions also affect outcomes. These are modifiable factors that couples can address before treatment.

Clinic expertise: IVF success rates vary between clinics based on laboratory quality, physician experience, and patient selection. Published success rates should be interpreted carefully as patient populations differ between clinics.

What Are the Risks and Side Effects of IVF?

IVF risks include ovarian hyperstimulation syndrome (OHSS) causing abdominal swelling and pain, multiple pregnancy if more than one embryo implants, ectopic pregnancy, and egg retrieval complications. Most side effects are mild, such as bloating, mood changes, and injection site discomfort.

While IVF is generally safe, it's important to understand potential risks and side effects before beginning treatment. Most complications are mild and manageable, but serious complications, while rare, can occur. Your fertility team will discuss these risks in detail and monitor you throughout treatment.

Ovarian Hyperstimulation Syndrome (OHSS)

OHSS occurs when the ovaries over-respond to stimulation medications, becoming enlarged and releasing chemicals into the bloodstream. Mild OHSS (affecting up to 20% of cycles) causes abdominal bloating, mild pain, and nausea. Severe OHSS (affecting 1-2% of cycles) can cause significant abdominal fluid accumulation, difficulty breathing, blood clots, and kidney problems.

Modern protocols have significantly reduced severe OHSS through careful monitoring, dose adjustments, and the use of GnRH agonist triggers instead of hCG in high-risk patients. If you're at high risk for OHSS, your clinic may recommend freezing all embryos and delaying transfer until the following cycle.

Multiple pregnancy

Transferring multiple embryos increases the chance of twins or triplets. Multiple pregnancies carry higher risks including premature birth, low birth weight, gestational diabetes, and preeclampsia. Single embryo transfer has become standard practice to minimize this risk while maintaining good success rates.

Egg retrieval complications

Egg retrieval carries small risks of bleeding, infection, or damage to nearby organs (bladder, bowel, blood vessels). These complications are rare (less than 1%) and are usually manageable with appropriate treatment.

Common side effects

Most women experience some side effects during IVF, though they're usually mild:

• Bloating and abdominal discomfort during stimulation
• Mood changes from hormonal fluctuations
• Injection site reactions (bruising, soreness)
• Headaches
• Hot flashes (during down-regulation)
• Breast tenderness

Can Embryos Be Frozen for Future Use?

Yes, high-quality embryos not transferred can be frozen (cryopreserved) using vitrification, a rapid-freezing technique with excellent survival rates (95%+). Frozen embryo transfer (FET) success rates are now comparable to fresh transfers. Embryos can be stored for many years.

Embryo cryopreservation has become an integral part of modern IVF, offering significant benefits for patients. When an IVF cycle produces more high-quality embryos than can be safely transferred, freezing the extras preserves them for future use. This can reduce the need for additional stimulation cycles and egg retrievals.

Modern vitrification techniques have revolutionized embryo freezing. Unlike older slow-freezing methods, vitrification rapidly cools embryos to prevent ice crystal formation, which can damage cells. Survival rates after thawing now exceed 95%, and success rates with frozen embryo transfer are comparable to - and in some cases better than - fresh transfers.

Benefits of frozen embryo transfer

Reduced OHSS risk: For women at high risk of ovarian hyperstimulation, freezing all embryos ("freeze-all" strategy) and transferring in a subsequent cycle allows hormone levels to normalize before transfer.

Better uterine receptivity: Some research suggests the stimulated cycle may not provide optimal conditions for embryo implantation. Transferring in a subsequent natural or medicated cycle may improve receptivity.

Cost efficiency: Frozen cycles are less expensive than fresh IVF cycles since they don't require ovarian stimulation or egg retrieval. This makes additional attempts more accessible.

Family planning flexibility: Frozen embryos allow couples to expand their family in the future without repeating the full IVF process. This is particularly valuable for women concerned about declining fertility with age.

Long-term embryo storage

Frozen embryos can be stored for many years without apparent decrease in quality. Children born from embryos frozen for over 20 years have been reported with no increased health concerns. However, clinics have policies about maximum storage duration, and there are typically ongoing storage fees.

Couples should discuss what they would like to happen to unused frozen embryos - options include future use, donation to other couples, donation to research, or disposal. These decisions can be emotionally complex and are best discussed before freezing embryos.