Embryo Transfer Process Explained

embryo transfer processEmbryo transfer process refers to the procedure that places an embryo into the uterus in an in vitro fertilization cycle. IVF cycles are also called intracytoplasmic sperm injection cycles or ICSI cycles. Implantation success rates range from 10% to 60% and are dependent to a large extent on the woman’s age as well as her health, which are the main determinants of transfer capacity.

Embryos are usually implanted two to three days after fertilization. This is known as the cleavage stage. They can also be transferred when at the blastocyst stage. This is around five to six days after fertilization. The embryos are rarely implanted during the morula stage on day four.

The embryo implantation procedure varies from clinic to clinic. Below is the general procedure on how embryo transfer is done.

What is Embryo Transfer? Embryo Transfer Process Explained

During the cleavage stage good quality embryos are collected from the group of fertilized eggs. These are set aside for implantation later on.

In healthy women aged under forty, two good quality embryos can be implanted in the womb.

In healthy women over forty, three embryos can be implanted. If you are over forty and are using donated egg cells, only two embryos are needed. Egg donors are required to be no older than thirty five years old.

You may have more than three good quality fertilized eggs. If your partner has a low sperm count, it may be best to save the extra ones. You can have the extra embryos frozen and have them implanted later.


Cryopreservation is a procedure that preserves body tissues by cooling them at extremely low temperatures. At sub-zero degrees, biological activities (e.g. cell aging) are successfully stopped. At cryogenic temperatures, there is no cell damage. But when you lower the temperature to approach cryogenic temperatures, the cells can burst. Without cryoprotectant chemicals to protect the body tissue, the cells get damaged during the freezing process. Popular cryoprotectants include glycerol, sucrose and dimethyl sulfoxide. Some penetrate the tissue and some protect it from the outside.

During the freezing process, water turns to ice. This excludes the solutes, making the remaining cryoprotectant solution more concentrated and harsher than normal. High concentrations of cryoprotectant solutes can be toxic to your embryos and can cause damage to the embryo and predispose you to miscarriage.

Cryoprotectants in nature

Random ice formation can also damage the embryo. Ice-nucleating agents (INA), a natural cryoprotectant, work by defining where ice will form in the tissue. By deliberately setting where ice will grow, widespread supercooling can be avoided and the destructive effects of intracellular ice growth can be reduced. Plants and insects have naturally occurring INA proteins that protect them during winter.

Anti-freeze proteins (AFPs), another natural cryoprotectant, work by lowering the freezing point of water while not altering the boiling point. AFPs prevent ice formation until after an extremely low temperature is reached. This action reduces the damaging effects of the freezing process.

Embryo transfer process

Embryo transfer process begins with your doctor inserting a speculum into the vagina to keep the vaginal walls open. Your doctor will then insert a catheter or a flexible slim tube through your cervix and into the uterus. Ultrasound can be used to provide the doctor with a better visual. Your good embryos are injected to the womb through the catheter.

Bed rest is recommended after the embryo transfer process.

Around fourteen days after the embryo transfer process, your doctor will give you a pregnancy blood test. If the result is positive, you will have a scan two weeks later. Following the procedure avoid stressful situations and a busy lifestyle. The first three months are critical to the success of your pregnancy.

What are your thoughts on freezing embryos for later? Have you had your embryos frozen? Would you donate them if you won’t use them? What was your experience like with embryo transfer process? Would love to hear from you!

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About the Author: Iva Keene MRMed. ND. - Natural Fertility Specialist

Iva Keene is co-founder, creator and award-winning author of the NFP Program and director of Natural-Fertility-Prescription.com. She holds a Bachelor Degree in Health Science in Naturopathy and a Master Degree in Reproductive Medicine. She has been a qualified and internationally accredited Naturopathic Physician for over 15 years. Since founding NFP in 2008, Iva’s articles, videos, guides, and reports have reached over 1.3 million people. Iva has dedicated her professional life to supporting couples on their path to parenthood with scientifically grounded information, protocols, and coaching around preconception care, natural infertility treatments, and integrative reproductive health.