Did you ever wonder why embryo transfers can be fresh or frozen? Dr. Levi and the Park Avenue Fertility team are here to guide you through your treatment process and help you understand the differences between fresh and frozen embryo transfers.
History of Embryo Transfers
When in vitro fertilization (IVF) was first developed, fresh transfers were the only type of transfer available. This is because the science of cryopreservation–the freezing of embryos for future use—was in its infancy. In the 40 plus years since the first embryo was transferred successfully, cryopreservation techniques, culture media (the environment where the embryo grows) and advanced reproductive technologies have improved tremendously, thus making both fresh and frozen embryo transfers (FETs) commonplace. FETs are now the preferred transfer type, but both are used regularly.
The Difference Between Fresh and Frozen Embryo Transfers
Fresh Embryo Transfers
A fresh embryo transfer typically occurs 5 days after a patient’s eggs are retrieved. The eggs are fertilized with sperm in the laboratory, and the resulting embryo is grown and monitored closely. The main benefit of a fresh embryo transfer is that there is a shorter time to conception, since there is only a 5 day waiting period between egg retrieval and embryo transfer into the uterus. Also, many insurance companies do not cover the cost of cryopreservation, so some patients choose fresh transfers for financial reasons.
There are some contraindications for fresh transfers. If a patient’s progesterone level is elevated, a fresh transfer should not be done, as this would negatively affect embryo implantation. Similarly, if a patient is at risk for hyperstimulation from the medications used to induce egg maturation, a fresh transfer could be dangerous for the patient.
Frozen Embryo Transfers
A frozen embryo transfer usually occurs 6-8 weeks after the embryo is frozen. When the patient is ready for transfer, she is given medications to mimic a natural menstrual cycle, and the FET date is coordinated with the cycle to optimize implantation.
If a patient wishes to have her embryos tested for genetic abnormalities, a FET is required. Preimplantation genetic testing (PGT) is performed shortly after egg retrieval. The embryo is biopsied (a small sample is taken from the embryo), and that sample, which contains the DNA of the embryo, is evaluated for chromosomal and genetic abnormalities. Once PGT is completed, the embryologist is able to choose only chromosomally normal embryos for transfer. By transferring only normal embryos, pregnancy success is greatly improved.
Frozen embryo transfers can also be used for subsequent pregnancies years later since embryos can be stored indefinitely. Similarly, if a patient wishes to preserve fertility because of age, cancer treatment or other reasons, embryos can be created for later use, and when ready, and FET would be performed.
If you are ready to begin your fertility treatment and would like to learn more about fresh and frozen embryo transfers, contact us to schedule a visit today.