Find out all about the embryo transfer process and the risks and chances of success with IVF or ICSI.

Key Facts

• Embryo transfer is the placement of an embryo into a woman's uterus as part of assisted reproductive technology
• The transfer occurs 2 to 5 days after egg retrieval
• The pregnancy rate from embryo transfer ranges from 20% to 40%, varying with the woman's age
• Women under 38 are typically recommended to have one embryo transferred to reduce the risk of multiple pregnancies
• Embryo transfer is usually painless and doesn't require anesthesia

Introduction

In vitro fertilisation (IVF) offers hope to couples struggling with infertility. This method involves fertilising an egg outside the body and then transferring the resulting embryo into the uterus. Millions of babies worldwide have been born through IVF treatment.

For couples undergoing IVF or ICSI (intracytoplasmic sperm injection) treatment, embryo transfer is the final step before the pregnancy test.

This article explains the embryo transfer process, available options and important considerations.

What is Embryo Transfer?

Embryo transfer is the process of placing an embryo into a woman's uterus. First, egg cells are fertilised with sperm. The resulting embryo is then cultivated in an incubator for several days before being transferred to the woman's womb on the second, third or fifth day.

During this ultrasound-guided procedure, your fertility doctor can visualise the optimal position for the transfer catheter containing the embryo.

Embryo Transfer Procedure

1. Preparation: Embryo transfer typically occurs 2 to 5 days after egg retrieval, also known as oocyte pickup (OPU). Before the transfer, the uterine lining is prepared for embryo implantation, usually by administering progesterone.
2. Transfer: The embryo transfer is a straightforward procedure, usually performed without anesthesia and similar to a Pap smear. It often takes less than 15 minutes. The reproductive physician inserts a speculum into the vagina and performs an ultrasound scan. Then, a thin, flexible catheter is inserted through the cervix into the uterus. The embryo is drawn into the catheter and gently released into the uterine cavity. The catheter is then carefully withdrawn.
3. After the transfer: Following the embryo transfer, you can usually return home after a brief rest period. It's advisable to take it easy physically for the next few days, though you can maintain your normal daily routine. About two weeks later, we'll conduct a pregnancy test to determine if the embryo transfer was successful.

Factors Influencing Embryo Transfer Success

• Embryo quality: High-quality embryos are associated with higher implantation, pregnancy, and live birth rates, as well as fewer pregnancy losses and prenatal complications. Both egg and sperm quality are crucial. Research shows that poor sperm quality significantly reduces embryo quality and blastocyst development rates.
• Number of embryos: The American Society of Reproductive Medicine recommends transferring only one good-quality embryo for patients under 38. In certain cases, such as advanced maternal age or multiple failed fertility treatment cycles, multiple embryos may be transferred. While this can increase the chances of successful pregnancy, it also raises the risk of multiple pregnancies.
• Endometrial condition: The uterine lining (endometrium) must be sufficiently thick and well-vascularised for successful embryo implantation. Studies indicate that clinical pregnancy and live birth rates decrease when endometrial thickness is less than 8 mm in fresh IVF cycles and less than 7 mm in frozen embryo transfer cylces.
• Doctor's experience: The expertise of the embryologist and the doctor performing the transfer can impact how the embryo is handled and placed in the uterus.

Types of Embryo Transfer

Various embryo transfer methods exist, depending on individual circumstances, timing, and the number of embryos transferred. These include:

Fresh Embryo Transfer (ET)

In a fresh transfer, embryos are transferrred from the incubator directly to the uterus 2 to 6 days after egg retrieval.

• Day 2-3 transfer: Embryos are in the cleavage stage (4-8 cells). Some fertility clinics prefer this early transfer to allow further development in the natural uterine environment.
• Day 5-6 transfer (blastocyst transfer): Embryos have reached the blastocyst stage (approximately 60-120 cells). Blastocyst stage embryos have a higher implantation rate compared to day 2-3 embryos.

A large study of 5,821 couples and women found that the live birth rate for fresh blastocyst transfers was between 32% and 41%, compared to only 31% for day 2 or 3 transfers.

Frozen Embryo Transfer (FET)

FET is used when there's a medical indication (e.g., ovarian hyperstimulation syndrome) or surplus embryos from previous treatments. Embryos are frozen —this process is called cryopreservation—, then thawed and transferred later. A frozen embryo transfer cycle also allows for genetic testing (preimplantation genetic testing, PGT) before transfer.

Single Embryo Transfer (SET)

SET involves transferring only one embryo, ideally a blastocyst. This approach reduces the risk of multiple pregnancies, which can pose increased health risks for both mother and children.

Multiple Embryo Transfer (MET)

In some cases, doctors may recommend transferring more than one embryo to increase pregnancy chances. However, this also increases the risk of multiple pregnancies. The number of embryos transferred depends on factors such as the woman's age and medical history.

Studies have shown that the live birth rate in IVF with SET is comparable to or even higher than MET.

While transferring multiple embryos can lead to more live births, it also increases the risk of medical complications for both mother and babies, such as premature birth and low birth weight.

Fresh vs. Frozen Embryo Transfer: What's the Difference?

Several factors influence the choice between a fresh embryo transfer and a frozen embryo transfer. Each procedure has its own advantages and disadvantages.

In both fresh and frozen embryo transfers, doctors analyze the endometrium's thickness and quality to ensure optimal conditions for implantation.

For fresh embryo transfers, doctors hormonally stimulate the ovaries to promote egg maturation and prevent premature ovulation. In contrast, frozen embryo transfers (FETs) don't use this hormone treatment. Instead, doctors administer progesterone to prepare the uterine lining for implantation.

Advantages of fresh embryo transfer

• Shorter treatment time: The potential for pregnancy is quicker as the embryo transfer occurs immediately after egg retrieval.
• Lower costs: This method reduces costs by allowing for direct embryo transfer after cultivation, eliminating the need for extra medications often required for FETs to suppress the menstrual cycle.

Advantages of frozen embryo transfer

• Possibility of preimplantation genetic testing (PGT): Embryos can undergo genetic analysis before transfer to reduce the likelihood of genetic abnormalities.
• No additional egg retrieval needed: If cryopreserved embryos are available, further hormonal stimulation and egg retrieval (follicular puncture) aren't necessary.
• Flexibility: Cryopreserved embryos remain viable for years and can be transferred at a later date. The survival rate after thawing is around 90%.
• Lower OHSS risk: The absence of ovarian stimulation significantly reduces the risk of OHSS.
• Better synchronization of embryo and uterine lining: Targeted preparation of the uterine lining can optimize implantation.

Preparing for Embryo Transfer

Embryo transfer occurs two to five days after fresh egg retrieval, or later if using frozen embryos from a previous treatment cycle. No special preparation is required on your part.

What to expect:

• The embryo transfer usually occurs without sedation, so you can eat and drink normally.
• A full bladder is helpful as it stretches your cervix, making it easier to visualize your uterus on ultrasound.
• To support implantation, your fertility centre will monitor your hormone levels and prescribe medication such as oestrogen and progesterone to build up the uterine lining optimally.

Additional steps you can take:

• Adequate hydration, a balanced diet rich in antioxidants, fiber, and low glycemic index carbohydrates, as well as stress reduction techniques, all contribute to creating an optimal uterine environment.

What to Consider after the Embryo Transfer

After the transfer, you'll have about 30 minutes to lie down and relax. However, you may get up earlier if you wish, as this isn't an invasive procedure.

Mild cramping and light bleeding may occur post-transfer. These symptoms don't necessarily indicate a problem.

Avoid strenuous physical activity, sexual intercourse, and saunas immediately after the embryo transfer.

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In this podcast episode you will discover the pros and cons of fresh and frozen embryo transfers and learn how to best prepare for your own transfer.

Frequently Asked Questions

When can I take a pregnancy test after the embryo transfer

Most clinics recommend waiting two weeks before testing. Taking a test too soon after the transfer often yields false results. This is because levels of hCG—the hormone measured in pregnancy tests—can vary. In early pregnancy, natural hCG production is often low, potentially leading to a misleading negative result.

For an accurate result, your fertility clinic will schedule an appointment for a blood test two weeks after the transfer.

How much does an embryo transfer cost?

If the embryo transfer is performed immediately after egg retrieval, the cost is typically included in your IVF or ICSI package. For a FET at Cada, the cost is approximately CHF 2,100, including medication.

How long does implantation take after an embryo transfer?

Embryo implantation usually begins 6 to 10 days after the transfer. However, the process can sometimes take longer.

How can I support implantation after the transfer?

While you can't directly influence the implantation process, you can create favorable conditions for your body. This includes managing stress, maintaining a balanced diet, and strictly avoiding alcohol and nicotine. Moderate exercise can improve blood circulation, potentially benefiting your uterine lining. Always take any medication prescribed by your doctor, such as progesterone.

What should I avoid after the embryo transfer?

In the days following the embryo transfer, avoid sexual intercourse and lifting heavy objects. Steer clear of hot baths or saunas, as heat can affect implantation. Refrain from strenuous exercise and don't take any medication or supplements without consulting your doctor first. However, bed rest isn't necessary.

What are the signs of a successful embryo transfer?

Unfortunately, there are no definitive signs of successful implantation. Some women report light bleeding (implantation spotting), abdominal discomfort, or breast tenderness, but these symptoms can have other causes as well.

When can I take a home pregnancy test after embryo transfer?

It's generally recommended to wait at least 14 days after the embryo transfer before taking a home pregnancy test. Testing too early can lead to a false negative result, as urinary hCG levels lag slightly behind blood hCG levels.

Key Takeaways

Embryo transfer is a crucial step in in vitro fertilization. The success rate of embryo transfer depends on various factors, including embryo quality, endometrial lining condition, and the woman's age.

To promote implantation, couples should follow certain guidelines after the transfer, such as avoiding sexual intercourse and strenuous activities. While embryo transfer enhances the chance of pregnancy, it's important to note that not every transfer is successful. Infertility can have multiple causes and often requires several treatment cycles.