UT Health Physicians

Frozen Embryo Transfer

With the advancement of assisted reproductive technologies, many more patients have embryos cryopreserved (frozen) after a fresh IVF stimulation. This is likely due to improved IVF stimulation techniques, improved laboratory environment for extended culture of embryos, development of new technologies for cryopreservation such as vitrification, and expansion of the use of preimplantation genetic testing (PGT). Within our clinic, 80-90% of cycles will have embryos cryopreserved. These cryopreserved embryos retain excellent viability despite the length of storage. In our laboratory, greater than 90% of cryopreserved embryos survive thawing.

The number of embryos transferred with a frozen embryo transfer is similar to that for a fresh embryo transfer and is based upon the guidelines established by the American Society for Reproductive Medicine.

When a patient desires to move forward with frozen embryo transfer, we may recommend a trial cycle if an endometrial biopsy or Endometrial Receptivity Assay needs to be performed. If you have been pregnant immediately before the FET cycle, we may recommend a repeat uterine cavity assessment with sonohysterogram (SHG) and/or a uterine measurement.

There are several different methods for preparation of the uterus to receive the embryo. The type of endometrial preparation does not appear to affect the live birth rate. However, several recent studies suggest that a natural cycle FET may be optimal to reduce the risk of pregnancy complications such as hypertensive disease of pregnancy, preterm birth, postpartum hemorrhage and placental issues.

A natural cycle FET (NC-FET) can still have multiple variations. In general, if a patient is having their own regular cycles, they can present for a cycle day 12 monitoring ultrasound. If the endometrial lining has an appropriate thickness and pattern, and there is a dominant follicle, a progesterone level will be checked to see if early ovulatory surge has occurred. If not, ovulation can be monitored with ovulation predictor kits or a trigger injection can be used to time the embryo transfer.

A programmed, or hormone therapy FET (HT-FET), may also have several variations. This is often recommended for patients with irregular menstrual cycles, for women who are post-menopausal, or for those who are using donor oocytes to create a fresh embryo for transfer. In general, a patient begins estradiol supplementation on day 3 of their natural menstrual cycle. A cycle day 12 monitoring ultrasound is used to assess the endometrial thickness and pattern. If this is adequate and there are no ovarian cysts, a progesterone level is checked to evaluate for ovulatory surge. If the progesterone is low, progesterone supplementation is initiated, and the embryo transfer is timed to the start of progesterone. The embryo transfer technique is similar to that of a fresh embryo transfer.

For patients with irregular cycles or ovulation disorders, and for patients who need to plan their therapy around time constraints, we can create an artificial menstrual cycle for FET. This involves treatment with an oral estrogen medication and is well established. Pregnancy rates are equivalent when compared to natural cycle FET.

Hormone Replacement - FET Cycle Overview

UT Health Fertility Center doctors are also faculty at The University of Texas Health Science Center San Antonio School of Medicine. This allows us to remain one of the most cost-efficient fertility practices in the area. Our staff is happy to answer questions about referrals, itemized diagnostic and treatment costs and billing options. The UT Health Fertility Center participates in a variety of insurance plans. For your convenience, we accept VISA, MasterCard, and Discover.

Natural Cycle - FET Overview