How Many Days After Period is Frozen Embryo Transfer

Introduction

A frozen embryo transfer, also known as FET, is a process of using a frozen embryo from a previous IVF cycle. The optimum time for transferring a frozen embryo at the 4-cell to 8-cell stage corresponds to cycle days 18 and 19. Frozen embryo transfer performed on the 17th to 20th days of the cycle can result in successful implantation. Embryo transfer can occur within regular ovulation or within 3 to 4 weeks after the last period for the woman with hormonal support FET IVF. The frozen embryos from a previous IVF or donor egg cycle are thawed and then transferred back into the woman’s uterus.

A successful in vitro fertilization (IVF) cycle can result in multiple embryos, and for a greater chance of being a parent, some people choose to freeze the extra embryos for future family building.

Preparation before freezing embryos

Before starting a cycle to retrieve eggs to make embryos, the doctor will test the hormone levels of the woman and perform an ultrasound to ensure that the ovaries of the woman are ready to begin the process of IVF. Then medicines will be injected that will stimulate the ovaries to grow multiple follicles, where eggs grow and can be easily harvested from.

To prepare for embryo implantation, the expected mother may be given estrogen pills or injections to build up the walls of the uterus, and then progesterone treatment is done to the woman to make the uterus receptive to the embryo.

Freezing embryos

When the fertility specialist determines that the woman is ready, the doctor harvests the eggs in an outpatient procedure performed under light sedation called egg retrieval. The number of eggs collected depends on the woman’s response to the hormone meditation. Then, the eggs can be frozen, and unfertilised.

To create an embryo, that is a fertilised egg, an embryologist fertilises one or more of the harvested eggs with the sperm (either a partner or a donor). The embryo is carefully observed as it grows in a petri dish for five to seven days. At this stage, embryos can be tested for genetic problems, especially if the egg or sperm donor or both are known to be the carrier of certain genetic conditions. The embryos are graded to determine the ones which are likely to grow successfully once implanted.

At this point, the previously highly graded embryos can be frozen. This process is also called vitrification. It replaces the water in the embryo cells with a protectant fluid, and flash-freezing with liquid nitrogen is used to prevent the formation of ice crystals that could damage the cells of the embryo.

Risk of freezing embryos

The risk of freezing embryos involves the collection of eggs from a woman through an egg retrieval procedure, including complications from the sedation and infection, or damage to the bladder, bowel, or a blood vessel from the needle inserted and catheter. A condition called ovarian hyperstimulation syndrome can occur when the ovaries are overstimulated by medicines. For the above reasons, patients are closely monitored during the process.

Benefits of frozen embryo transfer

• Frozen embryo transfer permits the environment to return to a normal state after IVF medication, providing natural embryo implantation conditions.

• FET reduces the risk of pregnancy of fresh embryo transfer IVF cycles, such as preterm labour, preeclampsia (high blood pressure disorder that can occur during pregnancy) and low birth weight.

• FET allows genetic screening, which greatly increases the chances of a successful pregnancy and healthy birth.

• FET preserves all viable embryos through embryo freezing, making the process of selection of single embryo transfer easier and thus greatly reducing the possibility of multiple gestations (pregnancy of twins or more) and the associated health risks.

• FET reduces or almost removes the risk of ovarian hyperstimulation syndrome (OHSS) during the transfer of the frozen embryo, which is a risk during fresh-cycle embryo transfers.

• FET is less expensive for multiple transfers than repeated fresh IVF cycles.

• Babies born from frozen embryos are likely to be healthier at birth.

• FET allows potential parents the flexibility to plan a family, save high-quality embryos at a young age, and move forward with implantation later. It also enables couples facing critical circumstances, such as cancer treatments, the chance to pursue having children after interfering treatments are completed.

Drawbacks of frozen embryo transfer

• A disadvantage of frozen embryo transfer is the possibility of the embryos not surviving the freezing or thawing process. However, since the survival rates of frozen embryos is exceeding 95%, the risk is minimal.

• Frozen embryo transfer involves additional time, as adding another month to the waiting time can be frustrating when trying to have a baby.

Storage of frozen embryos

Frozen embryos are stored and monitored in hospital facilities, generally in a laboratory, or commercial reproductive medicine centres. They can be carefully preserved for 10 years and even longer.

Notes

• Research has shown that frozen embryo transfers have increased implantation rates, increased live birth rates, decreased miscarriage rates, increased ongoing pregnancy rates and increased healthier babies.

• Success rates of frozen embryo transfer - for patients of age 35 or younger, there is a 60% pregnancy rate per embryo transfer, whereas women over the age of 40 have a 20% pregnancy rate for each embryo transfer.

• A frozen embryo after being transferred can split into two and form twins but the chances of splitting are quite less. In IVF, the chances of the embryo splitting into two are approximately one out of 100 transfers.

• Frozen embryo transfers provide a higher pregnancy success rate than fresh embryos during assisted reproductive technology.

• Research shows that day 3 embryos are best for transfer because they have 8 or more cells and show a significantly higher live birth rate. However, not all good-quality embryos follow the same process.

• The birth weight of babies born from frozen embryo transfers is on average 57.5g more than the birth weight of babies born from a fresh embryo transfer cycle, which is 93.7g less than that of naturally conceived babies.