Technical core and advantages
Modern embryo freezing technology, especially vitrification, greatly improves the survival rate of thawed embryos. Our clinical practice standard is freezing during embryonic development to the blastocyst stage (Day 5). According to our published medical research, most embryos with chromosomal abnormalities will experience developmental arrest during in vitro culture, unable to reach the blastocyst stage with better quality and stronger implantation potential. Therefore, selecting blastocysts that have developed to day 5 for freezing means selecting the embryos with the highest developmental potential, laying a solid foundation for future pregnancy success rates.
Survival rate and safety
Through vitrification freezing technology, the survival rate of thawed embryos is extremely high, with over 90% of blastocysts able to recover their activity intact. It should be clarified that a 90% survival rate does not directly equate to a 90% pregnancy rate, but such a high survival rate is a key prerequisite for achieving a high pregnancy rate. A large amount of medical evidence has confirmed that using embryos that have undergone freeze-thaw cycles for transplantation does not increase the risk of birth defects in newborns.
Standardized protocol for frozen embryo transfer (FET)
In order to maximize the success rate of implantation, precise drug preparation is required for the endometrium of embryo transplant recipients. The following is a standard FET solution process:
Cycle synchronization and ovarian suppression
Usually, the recipient will start taking oral contraceptives (BCP) during the early stages of menstruation.
Subsequently, daily injections of gonadotropin-releasing hormone agonists (such as Lupron/leuprorelin) were used in combination to suppress the ovulation function of the ovaries and prevent progesterone produced by spontaneous ovulation from interfering with the synchronous development of the endometrium. When withdrawal bleeding occurs, the dose of leuprorelin can be reduced as appropriate.
Endometrial preparation
After menstruation, intramuscular injections of estradiol valerate (E2V) are administered twice a week to promote endometrial thickening.
Evaluate the thickness and morphology of the endometrium by monitoring serum estradiol (E2) levels and transvaginal ultrasound. The ideal endometrial thickness usually needs to reach 8 millimeters or more. In some cases of poor endometrial response, vaginal estrogen or sildenafil (Viagra) vaginal suppositories can be supplemented to improve endometrial receptivity.
Progesterone conversion and support
When the endometrium reaches its ideal state, progesterone support is given. This usually starts 5 days before embryo transfer, and the most classic method is daily intramuscular injection of 50 milligrams of progesterone. The function of progesterone is to transform the proliferative endometrium into a secretory phase, preparing for embryo implantation.
For women who cannot tolerate injections, vaginal estrogen and progesterone suppositories are effective alternatives.
Embryo transfer and post pregnancy support
On the 6th day of progesterone support, transfer thawed blastocysts into the uterine cavity.
After transplantation, estrogen and progesterone will continue to be used until the 12th week of pregnancy. Other adjuvant medications may include dexamethasone (gradually reduced after 8 weeks of pregnancy) and antibiotics (used until the second day after transplantation). Prenatal vitamins should be taken throughout the entire preparation and pregnancy period.
