embryo transfer is the final step in the IVF process. In the final step, the embryo will be placed in your uterus through a simple procedure that usually does not require anaesthesia.
Two types of embryos can be used for IVF embryo transfer—fresh or frozen embryos. Surprised? Don’t be. Here’s all you need to know about the types of embryos and the factors to consider before choosing one.
What is fresh and frozen embryo transfer?
In the IVF process, eggs and sperm are fertilised outside the body and the fertilised eggs are kept in an embryo incubator, in a controlled lab setting, to facilitate their growth. The fertilised egg grows into an embryo within three to five days. Now, you have two options—either transfer fresh embryos to the uterus or save them through cryopreservation where they are frozen for later use. The frozen embryo could have been created weeks, months, or even years before the transfer.
You may choose fresh or frozen IVF embryo transfer; either way, the lining of your uterus (endometrium) must be prepared for the easy implant. In preparation for embryo transfer, your doctor will perform ultrasonography to check the thickness of the endometrium. In the case of fresh embryo transfer, the estrogen hormone made by the ovarian follicles will prepare the endometrium. However, in frozen embryo transfer, you may need to take hormone injections, patches, or pills to help the endometrium thicken.
We often consider anything “fresh” to be better than “frozen”. However, here, a frozen embryo is often a better choice. Besides the higher success rate, there are many other benefits of frozen embryo transfer.
Advantages of frozen embryo transfer in IVF
Some benefits of choosing a frozen embryo over a fresh embryo for IVF transfer include:
- There are more chances of success with Frozen Embryo Transfer (FET)
- Additional opportunities for transfer and more attempts at getting pregnant
- While attempting to conceive by a fresh embryo transfer, if you are unsuccessful, you can freeze the excess retrieved eggs and try later. No additional ovarian stimulation or egg retrieval is required
- FET is less costly than fresh cycles. After a fresh cycle, the subsequent FET cycles are less costly because there is no more egg retrieval. There may be multiple frozen embryo transfers after one egg retrieval. This gives you multiple pregnancy opportunities.
- If either of you has a hereditary genetic disorder, frozen embryo transfer gives you an opportunity for genetic testing
- FET prevents or eliminates ovarian hyperstimulation syndrome (OHSS). In most women, the symptoms of OHSS are mild. However, OHSS can cause cysts and the release of excess estrogen and progesterone hormone
- FET allows the separation of ovarian stimulation and embryo transfer. This reduces the chances of OHSS
- Frozen IVF embryo transfer increases the receptivity of the uterine lining to embryo implantation
- FET gives your body time to recuperate from an ovarian stimulation cycle and an egg retrieval process, thus allowing your endometrial layer to prepare better for egg implantation
- You can schedule the date of transfer in advance
- Babies born from frozen embryos are at a reduced risk of low birth weight
- These babies also have lower chances of being smaller than their gestational age
Scope of genetic testing in frozen embryo transfer
One of the major benefits of frozen embryo transfer is that if you or your partner suffer from any hereditary genetic disorder and want to go for genetic testing, you can do that with frozen embryos.
Preimplantation genetic screening (PGS) allows experts to examine the genetic composition of an embryo. The embryos that have an abnormal number of chromosomes are eliminated and those with the right number of chromosomes (46 chromosomes) are saved and used for IVF embryo transfer. This reduces the chances of genetic anomalies and miscarriages. Once incubated, an embryo biopsy is done after 5-7 days. A small cell sample is taken from each embryo for the biopsy. It is done to check if the embryos are normal. After the biopsy, only normal embryos are transferred to the uterus. If you are already aware of any genetic disorder in your family, then specific testing for that particular disease can be done.
Conclusion
Most couples undergoing IVF treatment find frozen IVF embryo transfer less stressful. It is believed that the success rate of frozen embryo transfer is very good among women above 35 years of age.
