Frozen embryo transfer
After ovarian stimulation with the IVF or ICSI process, we usually culture the embryos for three or five days and wait for embryo development. After embryo culture, we can transfer the embryos back to the patient at three or five days of development after egg retrieval. In some clinical practices, for several logical reasons, the embryos will be frozen and the transfer made in the following cycle. We call this ‘frozen embryo transfer’. Alternatively, we can make a fresh transfer on day three or day five after egg retrieval and keep the remaining embryos for freezing. Spare embryos from the previous IVF or ICSI cycle can be thawed and transferred again if the first transfer is not successful.
Frozen embryo transfer comprises endometrial preparation, checking the thickness of the endometrium by transvaginal ultrasound and settng the date for embryo transfer.
Endometrial preparation can be done in two ways. The first is using hormone preparation and the second uses the natural cycle but cannot be used in older women who no longer have ovarian function. We usually use hormone preparation instead of the natural cycle because the protocol can be used universally in all types of patients and the failure of unsuccessful stimulation is minimal compared with that of the natural one.
Endometrial preparation will be started on the second or the third day of the period. We usually check the hormone profile on day two or day three of the period to make sure it is the correct date of the period and start medication. We use Progynova (2 mg) and one tablet is taken four times a day (totalling 8 mg a day) for at least 14 days. Transvaginal ultrasound is done to check the thickness of the endometrium, which should be at least 8 mm at the mid part of the uterine cavity before we start progesterone for luteal support (pregnancy support). We also check progesterone levels to make sure that there is no premature ovulation and luteinization by natural progesterone before transvaginal ultrasound, which could lead to the wrong date for embryo transfer and the success rate would be low.
When the endometrial thickness is more than 8 mm and progesterone level is not detectable, a progesterone suppository can be used to prepare the endometrium for implantation. There are two types of progesterone vaginal suppository and oral form of progesterone on the market. All these medications are as effective as each other in supporting ongoing pregnancy. Progesterone duration usually corresponds with the stage of the embryo. For example, blastocyst stage embryos need five days of progesterone suppository before transfer.
They are different only in application. We usually use two types of both progesterone vaginal suppository and oral progesterone. The trade names of the progesterone suppositories are Cyclogest® Pessaries and Utrogestan® and can be administered by both oral and vaginal route. The trade name of oral progesterone is Duphaston®. All medications contain natural hormones.
No role of progesterone or hCG intramuscular injection
In past practice, some doctors still used intramuscular injection of progesterone in oil for as pregnancy support. We never use this method because it is a synthetic hormone that can produce congenital defects and there are many studies that have reported that progesterone vaginal pessaries are better than the intramuscular route for pregnancy support. Another hormone injection that was quite common in the past is Pregnyl®. This is synthetic hCG for triggering ovulation but it can also be used for pregnancy support. The adverse effects of Pregnyl® for pregnancy support are the increase in the risk of ovarian hyperstimulation syndrome and the false positive of pregnancy outcome (no pregnancy but the test shows that the pregnancy test is positive) if we check the blood test too early. We only ever use Pregnyl® for pregnancy support in exceptional cases where patients are allergic to progesterone.