Freezing embryos is a routine part of the IVF/ICSI process and approximately 70% of patients end up with some embryos in storage. Freezing embryos of excess good quality after IVF allows for the transfer of fewer embryos in the stimulated IVF cycle and, therefore, ensures fewer high-order (triplets or more) multiple births. This process provides patients with a “back-up” should the initial fresh embryo transfer not result in a pregnancy, at a much lower cost than starting IVF all over again and often with minimal medications.
- Higher frozen embryo transfer success rates have allowed many of our patients to achieve more than one pregnancy from a single cycle of ovarian stimulation. Embryos can be frozen at any stage of development during the IVF process.
- Eggs that are fertilized can be frozen as early as 1 day after an egg retrieval procedure, but it is more common to allow embryos to develop for a number of days before freezing them. This allows us to observe how well the embryos are developing so that only embryos with a good probability of establishing a pregnancy are frozen.
- Embryos tolerate freezing very well and we expect over 90% of embryos to survive the process. Pregnancy rates with frozen/thawed embryos are as good as pregnancy rates for embryos that were transferred fresh without ever being frozen.
Frozen Embryo Transfer
‘Frozen embryos’ is a term used to refer to those embryos that are not transferred during the index in -vitro fertilization (IVF) cycles and are subsequently cryopreserved.
A frozen embryo transfer can be used to produce a viable pregnancy by first thawing the frozen embryo, and transferring it into an appropriately prepared uterus.
It is a simple procedure wherein a patient is provided with hormonal medications to develop uterine lining, from day 3 of menses. Serial blood tests and ultrasound scans are done to monitor the uterine lining/endometrium. Then the optimal time in the patient’s cycle is determined and embryos are transferred into the womb.
- Ovarian hyperstimulation syndrome (OHSS).
- Inadequate uterine lining.
Frozen embryo transfer success rates:
The success rates of an FET cycle are comparable to fresh IVF cycles and sometimes result in a higher success rate because of the opportunity to optimize the lining of the uterus before implantation, among other reasons. Both fresh and frozen cycles have the same primary indicator for success: the maternal age at the time of embryo freezing.