Embryo transfer protocol and luteal support
Fresh embryo transfer: The ovulation induction protocol was chosen
according to the clinical characteristics of the patients. When the
dominant follicle diameter was ≥ 17 mm, recombinant human chorionic
gonadotropin (hCG) was injected, and ultrasound-guided transvaginal
oocyte retrieval was performed 36-38 hours after the injection.
HRT-FET cycle: For women with a previous history of a thin endometrium
or an irregular menstrual cycle, oral oestradiol valerate (Progynova,
Schering, Germany) 4-6 mg/d was administered from day 3 of menstruation,
and the dose was adjusted according to endometrial thickness. When
endometrial thickness reached 8 mm or more (with oestradiol valerate
continued for at least 10-12 days), progesterone gel (Serotonin, Merck
Serono, 90 mg/d) combined with dydrogesterone tablets (Duphaston, Solvay
Netherlands, 10 mg bid in the first two days, 20 mg bid later) was
administered prior to endometrial transformation. The Day 3 cleavage
embryo or the Day 7 blastocyst was thawed and transferred.
NC-FET cycle: For patients with regular menstrual cycles, ovulation was
monitored by transvaginal ultrasound, and cleavage-stage embryos were
transferred on the 3rd day after ovulation, whereas blastocysts were
transferred on the 5th day after ovulation. Dydrogesterone tablets
(Duphaston, Solvay Netherlands, 20-40 mg/d) were taken from the day of
ovulation until the 12th-14th day after embryo transfer.
After fertilization, the cleavage and development of embryos were
evaluated. Embryos available for transfer contained 4-8 blastomeres on
the 3rd day after fertilization and were graded 2 or
above. No more than 2 emtryos could be transferred and the remaining
embryos were cryopreserved. Embryos with more than 50% viable cells
after thawing could be transferred. The level of β-hCG in serum was
checked on the 12th-14th day after
embryo transfer. The appearance of an intrauterine gestational sac in
vaginal ultrasonography performed 4 weeks after embryo transfer was
diagnosed as clinical pregnancy. Progesterone gel (Serotonin, Merck
Serono, 1 time/d, 90 mg/d) was used for luteal support, fresh embryo
transfer and natural cycle medications were administered until the
8th-10th week of pregnancy, and the
artificial cycle was performed until the 12th week of
pregnancy.