Artificial Reproductive Technology (ART), or specifically, In-Vitro Fertilisation (IVF), gave the world the first IVF baby in 1978. The birth of Louise Brown gave infertile couples a new hope for biological parenthood.

Over the last three decades, IVF technology has evolved and advanced.

Ovarian stimulation has become safer and more patient-friendly.

Fertility laboratory techniques have also improved tremendously.

The most important breakthrough in these techniques is the ability to freeze and thaw embryos successfully.

The original method of freezing and thawing embryos was associated with higher embryo loss.

The current technique of embryo freezing, known as vitrification, has improved the embryo survival rate.

In an established IVF laboratory, the survival rate of thawed embryos with the vitrification technique is close to 100%.

In 1984, the first baby implanted via frozen embryo transfer (FET) was born.

Since then, many fertility clinics have adopted FET as part of their IVF protocol.

The embryo transfer procedure can be divided into fresh and frozen embryo transfer, based on the timing of the embryo transfer.

In a fresh embryo transfer, embryos are typically placed into the womb between two and five days after the egg collection procedure in the same period cycle.

In FET, embryos are frozen between day two and six after an egg collection.

The embryo(s) is then transferred into the womb at a later date, either in a natural period cycle or after the womb is prepared with medication.

IVF, FET, embryo, pregnancy,

A long tube device that contains a vitrification freezing platform for embryos and sperm in a liquid nitrogen tank. FET allows a more natural pregnancy experience as the embryo can be implanted after the woman ovulates in a natural period cycle. — Filepic

FET benefits

The benefits of FET are as follows:

Higher pregnancy rate

FET offers a higher pregnancy rate compared to fresh embryo transfer, especially for women who are more than 35 years of age.

For younger women, FET gives a similar, if not higher, pregnancy rate compared to fresh embryo transfer.

Every couple, regardless of their age, wants the highest pregnancy rate for their age in an IVF treatment.

FET can help them achieve it.

So, if you are going through IVF, discuss the advantages and disadvantages of FET with your fertility doctor.

Prevention of Ovarian Hyper-stimulation Syndrome (OHSS)

OHSS is a risk that every fertility doctor would like to avoid.

Typically, it happens during an IVF cycle among women who have Polycystic Ovarian Syndrome (PCOS).

Women who develop OHSS can become unwell after the egg collection procedure.

If she becomes pregnant in the same cycle, the OHSS can further worsen and increase her risk of complications such as fluid collection in the lung and abdomen.

She is also at risk of developing deep vein thrombosis and having a miscarriage.

The best strategy to eliminate or minimise the risk of OHSS is by freezing all the embryos.

This strategy allows the woman time to recover as FET can be done at a later date.

Pregnancy, IVF, FET, ovulation,

FET allows a more natural pregnancy experience as the embryo can be implanted after the woman ovulates in a natural period cycle. — Filepic

Ability to transfer the embryo at a later date

Couples with a busy work schedule sometimes have difficulty taking time off work to complete the entire IVF procedure in the same month.

FET allows IVF treatment to be completed in two parts.

The first part consists of ovarian stimulation, egg harvesting, and embryo formation and freezing.

The second part consists of FET, which can be done at a time when the couple is ready both physically and mentally.

Ability to do genetic screening on the embryo

To improve pregnancy rates and reduce miscarriages, embryos can be genetically tested before they are transferred into the womb.

This test is called Pre-implantation Genetic Screening (PGS).

PGS allows the doctor to choose a genetically-normal embryo to be transferred, thus improving implantation rates (i.e. pregnancy rates).

Typically, PGS is done when the embryos reach the blastocyst stage (day five or six after fertilisation).

The biopsied embryos are frozen while awaiting the results of the PGS.

FET is done a month later with the genetically-tested normal embryo(s).

Controlled progesterone hormone level

In a natural period cycle, an egg is made to ovulate every month in a woman’s ovary.

In an IVF cycle, medications are given to make more eggs grow (typically between eight to 10 eggs).

This high number of eggs leads to a higher level of hormones, which are produced by the developing eggs.

Higher levels of the progesterone hormone are known to reduce pregnancy rates.

This is because the higher level of progesterone makes the lining of the womb not conducive for embryo implantation.

In a FET cycle, the embryo is transferred after a woman ovulates naturally. This is known as natural cycle FET.

In a natural cycle FET, the progesterone level mimics the level that occurs in a natural conception, thus improving the pregnancy rate in a natural cycle FET.

Ability to do more than one embryo transfer procedure

The freezing and thawing technology allows excess embryos, after the initial embryo transfer procedure, to be frozen safely for later use.

FET gives a couple multiple embryo transfer opportunities without having to undergo multiple ovarian stimulation and egg collection procedures.

This gives couples an opportunity to have a larger family from a single IVF cycle.

Overall cost saving

IVF is an expensive treatment.

If the first embryo transfer attempt fails to give the couple a successful pregnancy, they have the ability to prepare for another embryo transfer via FET without the need to undergo a fresh IVF cycle.

Furthermore, FET is considerably cheaper compared to a new cycle of IVF.

In addition to financial savings, couples are spared the emotional burden of going through a fresh IVF cycle.

More patient-friendly

FET, when done during a natural period cycle, is very patient-friendly.

The embryo(s) is transferred three or five days after ovulation.

Ovulation can be monitored using commercial ovulation urine test kits that are easy to use.

Couples are relaxed as they have less need for medication pre- and post-FET.

The whole journey towards parenthood may mirror a natural pregnancy experience for the couple.

Dr Agilan Arjunan is an obstetrician and gynaecologist, and fertility specialist. For more information, e-mail The information provided is for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star does not give any warranty on accuracy, completeness, functionality, usefulness or other assurances as to the content appearing in this column. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.