What is the frozen embryo transfer (FET) procedure/timeline?
To transfer frozen embryos, your uterine lining, or endometrium, must be at the correct “phase” of development for implantation to occur. This is usually achieved with a combination of estrogen and progesterone.
Estrogen is administered orally, vaginally or transdermally (patch) for 2-4 weeks and the growth of the uterine lining is monitored with ultrasound. When the lining is of adequate thickness, progesterone is added and the embryo transfer is scheduled.
Once progesterone treatment has started, the transfer must occur within a very specific time frame to ensure that the developmental phase of the lining matches that of the frozen embryos.
How does an embryo transfer work?
Embryo transfer is generally not done under anesthesia. The number of embryos to be thawed and transferred will have been discussed by your physician prior to initiating your cycle. Rarely, embryos will not survive the thawing process and additional embryos, if available, will be thawed to reach the number planned for transfer.
Your physician and embryologist will review the status of your embryos with you prior to your embryo transfer. A blood pregnancy test will be performed around 9-14 days after transfer.
How many embryos can I transfer? Can I try for twins?
Together with your physician you will come up with a number of embryos to transfer. Based on the American Society of Reproductive Medicine (ASRM) and Society for Assisted Reproductive Technologies (SART) data guidelines for the limits on number of embryos to be transferred continues to support and promote singleton gestation and reduce the number of multiple pregnancies.
A twin (or higher multiple) pregnancy is much riskier to both the woman and the growing fetus/babies. The general goal is to have one healthy baby at a time.
Can I have genetic testing on my embryos?
Preimplantation genetic testing (PGT) is not necessarily a recommended component for all patients undergoing IVF, although the frequency of its use is rapidly increasing.
Preimplantation genetic screening (PGS or PGT-A) tests an embryo for an abnormal number of chromosomes which does increase with the aging of eggs.
PGS can also determine the gender of the embryo. Some of the common reasons a patient/couple might choose PGS are:
- Women 35 years or older
- Recurrent 1st trimester pregnancy loss
- History of chromosomally abnormal pregnancy
- Previous IVF failure
- Family balancing of genders
- Reduction of 1st trimester loss – improving efficiency of IVF
A chromosomally tested embryo will not always result in a pregnancy. Factors other than those tested (ie, specific genes), the metabolics of the embryo and the uterine environment all affect the pregnancy outcome.
Individuals who are known carriers of a specific genetic disorder (such as cystic fibrosis or Tay- Sachs) or chromosomal translocation or inversion may elect to do preimplantation genetic diagnosis (PGD or PGT-M) to identify embryos affected by the known condition.
What do I do with my remaining embryos?
If you have not yet completed your family, you can continue to store your embryos at the clinic or you may need to transfer them to a long term storage facility for future attempts at pregnancy. Typically, you must pay a monthly or annual storage fee. If you have completed your family, there are four main options regarding your remaining embryos:
- Dispose of your embryos
- Donate them to the lab for quality control (staff training and development)
- Donate them to another couple for reproductive purposes
- Donate them for scientific research
What is an Endometrial Receptivity Assay (ERA) biopsy?
The ERA biopsy is a test designed to identify the ideal window for implantation of pregnancy. For most women, this window occurs after the lining of the uterus has been exposed to five full days of the hormone progesterone. In some women, however, this implantation window can be skewed.
The ERA test will determine if additional or less progesterone exposure is needed and will help your physician determine the best protocol to use for your FET cycle prep. This test is ideal for women who have had recurrent failed FET cycles or recurrent miscarriages.
The test will be performed on the same day in your FET cycle prep that your FET would take place. The biopsy is typically performed as an in office procedure with no recovery time needed.