Protocols for frozen embryos transfer
Hormone preparation for FET
Using hormones to prepare the uterus is the most common way in which a frozen embryo transfer is performed. The first step is to suppress the pituitary gland. This is necessary to reduce the chances of ovulation occurring unexpectedly. Typically, Lupron is used for pituitary suppression. For most women, this will require approximately two weeks of daily Lupron injections.
The second step in a frozen embryo transfer cycle is to use hormones to duplicate the changes that normally occur in the uterus during a regular menstrual cycle. This requires the use of two hormone medications: estrogen and progesterone.
Estrogen preparation for FET
During a normal menstrual cycle, estrogen is produced by the developing follicle. This estrogen acts on the uterus to thicken and mature the uterine lining. Estrogen is given in a FET cycle for the same reason. There are many different ways that estrogen can be given in a frozen embryo transfer cycle:
- Estrogen pills – Estrace, Premarin
- Estrogen patches – Estraderm, Climera
- Estrogen injections – Delestrogen (estradiol valerate), Depogen (estradiol cypionate)
- Vaginal estrogen – Vagifem, Femring
There is no data that any one method works better than another and a method is usually chosen based on physician preference. [My Rx is for the patches, which I'll start tomorrow]
During the time when estrogen is given, the woman will come to the office periodically to be monitored. A transvaginal ultrasound is performed to determine the thickness of the uterine lining and a blood test is performed to look at the level of estrogen in the blood [fyi -- I'll be doing this at an imaging center rather than going to my local RE -- the imaging center is in-network (and my local RE is not) and they were very friendly at the imaging center (and my local RE no longer is now that we've gone to a different clinic)]. On occasion, if the lining is not thickening as it should, the dose or type of estrogen must be increased or prolonged. The length of time the estrogen can be given is very flexible. During this phase, for example, the duration of estrogen may be prolonged to delay the day of embryo transfer to accommodate the patient’s schedule.
The monitoring in a thaw cycle is very flexible. Unlike a fresh IVF cycle during which the required days for monitoring are determined by the growth of the follicles in the ovary, in an FET cycle, the days can be adjusted at any time. Thus, a frozen embryo transfer cycle is much less stressful on the patient. [although I think this is just this person's opinion I'm guessing. I'm sure some women find the waiting of FET more stressful than a fresh transfer]
Progesterone in an FET cycle
Once the uterine lining has been thickened sufficiently, progesterone is added. Once the progesterone is added, the Lupron may be stopped. Progesterone matures the uterine lining and makes it receptive to an embryo to implant. Once the progesterone is begun, there is a certain “window of implantation” during which the embryo must be transferred. The stage of the embryo must match the stage of development of the uterus. Therefore, the only factor that locks the patient into performing the transfer on a certain day is starting the progesterone. Once the progesterone is begun, if the embryo transfer is not performed on a certain day, the cycle must be cancelled and a new preparation with hormones must be begun after allowing a period to occur.
There are many different types of progesterone that can be used in a frozen embryo transfer cycle. Some of the more common methods include:
- Progesterone pills – Prometrium
- Progesterone injections
- Progesterone vaginal suppositories
- Progesterone vaginal gels – Crinone, Procheive
There is considerable uncertainty in the medical literature concerning which type of progesterone is the best for FET cycles. Again, the choice of progesterone for an FET cycle is up to the discretion of the physician. A few things, however, most experts would agree on. Progesterone given by mouth is unreliable due to variable absorption and subsequent metabolism in the liver. [my Rx is for suppositories -- 3x per day]
Once the uterine lining is adequately thickened with estrogen, the progesterone is usually started on a particular day to allow for scheduling of the embryo thaw and embryo transfer for a time that is convenient for the in vitro fertilization laboratory staff.