What is an embryo transfer?
Embryo transfer is the final step in the IVF (in vitro fertilization) process, in which the embryo developed in the IVF lab is transferred to the woman’s uterus for pregnancy. This transfer can be of a frozen embryo or of a “fresh embryo,” which is one that has not been frozen.
Frozen embryo transfer
This is the more common form of transfer. After the egg is fertilized by sperm in the IVF lab it is cryopreserved (frozen and stored). Once frozen, embryo transfer can occur anytime in the future, which provides more flexibility for the patient.
Frozen embryos are the only ones eligible for preimplantation genetic testing (PGT). PGT evaluates the embryo for genetic issues that can cause implantation failure, miscarriage or birth defects in a child.
Fresh embryo transfer
Transferring a fresh embryo generally occurs 3-6 days after the initial egg retrieval. In that time the sperm fertilizes the egg in the lab and it develops into an embryo. The transfer is generally performed when the embryo reaches the blastocyst stage, which is usually day 5-6 of embryo development. The American Society for Reproductive Medicine (ASRM) states transferring an embryo during the blastocyst stage has advantages over transfer earlier in the cleavage stage.
Related reading: How to prepare for an egg retrieval
Fresh vs. frozen transfer
Studies show little to no difference in pregnancy success or live birth rates between the two options.
Fresh transfer pros
- Faster route to pregnancy.
- Potentially lower cost due to no freezing and storage fees.
Cons
- After egg retrieval, the stimulating medications can negatively affect the uterine lining’s ability to receive the embryo.
- Increased risk of ovarian hyperstimulation syndrome (OHSS) as pregnancy naturally increases human chorionic gonadotropins (hCG), which were recently administered for egg stimulation resulting in too much hCG.
Frozen transfer pros
- The woman has time to recover from stimulation, potentially improving the uterine lining’s receptivity.
- Flexibility: Many women prefer more time in between the two steps.
- Lower risk of OHSS due to longer interval between egg retrieval and transfer.
- The ability for embryo genetic testing.
- Embryos available for future pregnancies.
Cons
- Slight risk of embryos not surviving the freeze and thaw process.
At Ember, everyone is a VIP – very important patient
How to prepare for embryo transfer
Knowing what to expect in this procedure can help patients avoid anxiety and relax for a more comfortable experience. It is not as intensive as many expect, and most women tolerate the procedure well.
Your Ember fertility specialist Dr. William Freije explains all aspects of the procedure beforehand. He and other members of the Ember clinical staff make sure the patient is at ease.
To help prepare mentally for the procedure, patients can work on reducing stress. Get plenty of sleep, particularly the night before the embryo transfer. Avoid overworking. Practice stress management techniques such as controlled breathing, meditation, yoga, acupuncture, moderate exercise and activities you enjoy.
How patients can prepare their uterine lining
We also encourage women to do all they can to prepare their uterine lining to receive the embryo for successful implantation. The proper thickness of the lining is important for success. Having the proper nutrients and good circulation can help strengthen the uterine lining.
Following are some things a patient can do on her own, beginning as long before the procedure as possible.
Eat healthy
The right balance of proteins, carbohydrates and healthy fats such as omega-3 helps promote uterine lining health. Fiber is important as is maintaining the proper blood sugar levels. Eat whole grains and lots of vegetables and fruits. Increase water intake.
Maintaining a healthy weight is beneficial for transfer success. A high BMI (body mass index) decreases pregnancy success.
Things to avoid
Avoid or limit red meats, refined grains, and high-salt and highly processed foods. Steer clear of caffeine and limit alcohol consumption – abstain from alcohol once pregnant. Stop smoking. Avoid overheating the abdomen by using hot tubs or saunas before transfer.
Embryo transfer FAQ
How does embryo transfer work?
A fertility specialist inserts an embryo developed in the IVF lab into the woman’s uterus for pregnancy. Transferring the embryo is the last step in IVF.
How long after embryo transfer does implantation occur?
The embryo typically implants (attaches to the uterine lining) 1-5 days after transfer. Pregnancy can be confirmed about two weeks after transfer.
Is embryo transfer painful?
No, the transfer is not painful. No anesthesia is involved and the transfer generally only causes mild discomfort, similar to having a Pap smear test. Some women may experience light spotting, cramps, bloating and fatigue afterward.
Should I transfer 1 or 2 embryos?
Most women who are healthy and not of advanced age are encouraged to transfer one embryo to avoid increasing the risks associated with having twins. Transferring two embryos is also an option, depending on the individual’s situation. (See below.)
What to expect after embryo transfer?
Expect a short rest after the procedure in the clinic before going home and a few days of avoiding strenuous activities.
How many embryos to transfer?
This is a question many people have, and the answer depends on each person’s situation. Primary factors are the woman’s age, health conditions, medical history and embryo quality. Embryo quality is judged by our embryologist or PGT, which is possible only with frozen embryos.
Transferring a single embryo is the preferred option as it reduces the chance of a multiple pregnancy (twins or more), which carries risks for mother and baby. Sometimes the woman’s medical condition and/or her advanced age makes transferring two embryos the better choice for success.
The transfer procedure
- First, we assess the patient’s endometrial lining through blood work and ultrasound.
- For about three weeks prior to transfer, the woman takes medications to prepare her womb for implantation and pregnancy. Generally these are estradiol at first followed by progesterone.
- With a fresh embryo, the transfer occurs when the embryo in the lab has reached the appropriate stage after egg retrieval and fertilization. With a frozen embryo, our embryologist skillfully thaws the embryo to time the transfer for when the woman’s uterine lining is ready for implantation.
- The transfer is carefully done by our fertility specialist using a soft catheter containing the embryo. This is guided by ultrasound through the cervix and into the uterus. The patient should have a full bladder, which aids in ultrasound visualization.
- The procedure itself takes about 15 minutes; the patient’s total time at our clinic will be about three hours.
What to do afterward
- The patient will rest for a short period before going home.
- We give women all the advice they need on follow-up care and any recommended medications for their personal situation.
- For a few days the patient shouldn’t do strenuous exercise, take baths or have sexual intercourse.
- During the two-week wait period before a pregnancy test, women should try to reduce their stress.
Embryo transfer success rate
Embryo transfer success rates are about the same for fresh embryo and frozen embryo transfers. Transfer success rates are similar to IVF success rates, as embryo transfer is the last step in IVF. According to a National Library of Medicine study, around 40% of IVF cycles result in successful birth. This number increases with additional IVF cycles.
Ember’s success rates transferring frozen embryos
Ember’s frozen embryo transfer rate of successful birth across all age groups is around 50%. This is partly due to the fact that more than 95% of frozen embryo transfers at Ember involve PGT-A, which screens embryos for aneuploidy genetic defects that decrease implantation rates and pregnancy success.
Regarding general frozen embryo transfer success at Ember, Dr. Freije tells patients that if he transfers three frozen embryos to three different patients, two will get pregnant and one will not. Note that live birth does not always occur after pregnancy success.
Factors in embryo transfer success include:
- Age of the woman.
- Whether the woman is obese.
- Number of embryos transferred.
- Stage of embryo development at transfer, with blastocyst stage more successful.
- Skill of the fertility specialist conducting the transfer and of the lab handling the embryos.
ASRM notes that studies show that embryo transfer success rates differ by the specialist performing the transfer.
Ember’s expertise in embryo transfer
- Ember’s fertility specialist Dr. William Freije has developed expert skills through his experience in embryo transfers, enabling him to customize the procedure to maximize individual patients’ success.
- Lab & Science Director Dr. Avisa Asemi has over 20 years of IVF lab experience in embryo transfer and all areas of laboratory leadership. She holds the highest lab certifications: High-Complexity Clinical Lab Director, Technical Supervisor and Embryology Laboratory Scientist.
- Our IFV lab is state-of-the-art including time-lapse embryo monitoring. All our embryology practices including transfer are rigorously reviewed and updated.
