What is frozen Embryo Transfer?

A frozen embryo transfer (FET) is a treatment cycle where a frozen embryo from a previous fresh IVF cycle is thawed and transferred back into a woman's uterus. This means you won't have to undergo another cycle of hormone stimulation and an egg collection. Frozen embryo cycles can be undertaken on your natural cycle (Natural cycle HRT) or using hormone preparation (HRT-FET).

Natural cycle FET: This can be done if you have regular ovulatory cycles. Your cycles would be monitored by regular scans for follicular growth and ovulation and the embryos are transferred at the appropriate time following ovulation.

Hormone Replacement Treatment -FET: Your natural cycle is suppressed by giving hormonal medication to prepare the uterus. Once the lining of the uterus is ready, the embryos are transferred at the appropriate time.

Why do we freeze embryos?

  • Risk of Ovarian Hyper stimulation Syndrome
  • Thin or thick endometrium
  • Fluid in the endometrial cavity
  • Endometrial polyp.
  • Pre HCG triggerhigh Progesterone level.
  • Donor oocyte IVF cycle.
  • Extra frozen embryos are available after fresh embryo transfer cycle.
  • Success results are better than fresh transfer in some centres.
  • On couple’s request

What are the benefits of FET?

1) Increase the success rate

2) Avoid the risk of ovarian hyperstimulation syndrome (OHSS)

How is FET treatment done?

Embryos are thawed in the morning of the scheduled frozen embryo transfer. Approximately >90% of embryos survive cryopreservation and thawing. Embryo transfer is done under ultrasound guidance which will require the bladder to be full.  It is similar to IUI procedure. A small plastic catheter is passed gently through the cervix into the uterus. Embryos are deposited in the endometrial cavity. No anaesthesia is required for the embryo transfer. You will be discharged after resting for 30 minutes, but you can take rest for 1-2 hours.

How many embryos are transferred?

We usually transfer one or two day 5 embryos (blastocyst stage) during each FET cycle. The transfer of more embryos may increase the likelihood of multiple pregnancies, which increases the pregnancy risks for the woman and the foetuses.

What is the success rate of FET treatment?

The success rate is approximately 60-70%.

What are the medications to be continued?

Oral Medicines, vaginal gel and vaginal capsules which are already been prescribed before need to be taken regularly on time. Not to stop them until you speak to the doctor. Not taking or skipping the medicines can adversely affect the pregnancy test results. On confirmation of pregnancy test, discuss with the doctor and these medications need to be continued until 10-12 weeks of pregnancy.

What are the advices to follow after embryo transfer?

We advise you to take adequate rest at home for 3 days after embryo transfer. Complete bed rest is not required. You can do routine work at home.  After 3 days, you can be normal as before. Avoid sex, heavy exercises and heavy work until further advice. You can travel and resume your routine office work after 3 days. You can do walking and yoga. You can avoid long journeys.

How is embryo freezing done?

Embryos can be frozen from day 2(4 cell stage) to day 5 (Blastocyst). They are placed in the thin straws, sealed at both ends and labelled with patient’s name, husband’s name and identification number. Embryos are then frozen where the temperature rapidly drops to below -150 degree Celsius by vitrification process. These straws are then placed in goblets and put into the cryotanks filled with liquid nitrogen, which maintains the temperature by -196 degree Celsius.

What to do with the remaining frozen embryos?

  • Embryos can be utilised in the future to have second baby.
  • Once the family is completed, the embryos can be discarded
  • With couple’s permission, can be used for research and training.


What are the risks and benefits of fresh and frozen embryo transfer?

Fresh embryo transfer has high risk ofsmall for gestational age baby, low birth weight baby, pre eclampsia, preterm birth, placenta previa, Placental abruption and perinatal mortality.

Frozen embryo transfer has high risk oflarge for gestational age baby &macrosomia, hypertensive disorders in pregnancy, postpartum haemorrhage and post term birth 

Stimulated cycles had outcomes similar to natural cycles; the results suggest a link between the absence of corpus luteum and adverse obstetric outcomes.