Accumulation of Vitrified Embryos Followed by Frozen Embryo Transfer in Poor Ovarian Responders According to Bologna Criteria

Background: The aim of current study is to compare the pregnancy outcome between natural cycle IVF-ET (NC group) and frozen ET following accumulation of vitrified embryos (ACC-E group). Methods: The ACC-E group included 38 frozen ETs in 30 patients and the NC group included 92 natural or modified IVF-ET cycles in 91 patients. In the ACC-E group, natural cycle or modified natural cycle with minimal stimulation was used for follicular growth. Embryos were frozen by the vitrification method for several rounds and then thawed embryos were transferred. Results: Ongoing pregnancy rate (15.8% vs. 8.7%; p=0.24; Ψ=0.1), and live birth rate (15.8% vs. 6.6%; p=0.1; Ψ=0.14) were comparable for ACC-E versus NC group, respectively. However, even though the effect size was small, the chemical pregnancy rate of the ACC-E group was significantly higher than that of the NC group (31.6% vs. 11.9%; p=0.02; Ψ=0.23). Conclusion: Accumulation of vitrified embryos followed by frozen ET can be considered as a new strategy to improve pregnancy rate in poor ovarian responders. Page 2 of 4 Citation: Kwon H, Choi DH, Kim EK, Kim EH, Lee SE (2015) Accumulation of Vitrified Embryos Followed by Frozen Embryo Transfer in Poor Ovarian Responders According to Bologna Criteria. Gynecol Obstet (Sunnyvale) 5: 331. doi:10.4172/2161-0932.1000331 Volume 5 • Issue 10 • 1000331 Gynecol Obstet (Sunnyvale) ISSN: 2161-0932 Gynecology, an open access journal group included 38 thawing ET cycles in 30 patients whereas the NC group included 92 fresh ET cycles in 91 patients. ACC-E and NC protocols In the ACC-E group, a natural cycle or modified natural cycle with minimal stimulation was used for follicular growth. Antagonist (Cetrotide® 0.25 mg per day; Merck Serono, UK) was injected subcutaneously when a leading follicle reached 14 mm diameter in the modified natural cycle. hCG (Ovidrel®; Merck Serono, Italy) was administered when a leading follicle with a mean diameter ≥18 mm was observed on ultrasonography in natural or modified natural cycle. Oocytes were retrieved 35 hours after hCG injection and subsequently fertilized by IVF or intra-cytoplasmic sperm injection (ICSI). Embryos were frozen by the vitrification method described below. Embryos were pre-equilibrated in dPBS (Irvine, CA, USA) +1.5 M ethylene glycol (EG; Sigma; 102466; USA) +20% (v/v) synthetic serum substitute (SSS; Irvine, CA, USA) at 30°C for 2 min 30 sec and equilibrated in dPBS+5.5 M EG+ 1.0 M sucrose (Sigma; S-1888) + 20% (v/v) SSS (Irvine, USA) at 30°C for 20 sec before mounting on electron microscopy (EM) gold grids and immediate submersion in liquid nitrogen at -196°C. For thawing, embryos on EM gold grids were sequentially transferred to thawing solution containing 1.0, 0.5, 0.25, or 0.125 M sucrose in dPBS at 37°C at intervals of 2 min 30 sec. After four to six washes with 20% SSS in dPBS, embryos were placed into culture medium as described previously [16,17]. The thawed embryos were transferred on postovulation day 3 without hormonal addition in patients who were having a regular menstrual cycle or on the third day after endometrial thickness ≥8 mm was observed with administration of estradiol valerate (Progynova®; Schering, South Korea) in a hormonally manipulated artificial cycle. Micronized progesterone (Utrogestan® 200 mg Vaginal Capsule; Capsugel, France) was inserted into the vagina three times per day beginning on the day of ovulation for subjects in natural cycle. For those in hormonally manipulated artificial cycle, micronized progesterone was commenced when endometrial thickness was ≥8 mm. In the NC group, follicular growth, oocyte retrieval, and fertilization were performed according to the natural or modified natural cycle IVF protocol as described above. Embryos were transferred on postretrieval day 2 or 3. Micronized progesterone (Utrogestan® 200 mg Vaginal Capsule; Capsugel, France) was inserted into the vagina three times per day beginning on the day of oocyte retrieval for luteal support. Pregnancy was determined by serum level of β human chorionic gonadotropin (hCG) 13 days after embryo transfer. For the ACC-E group, the following factors were recorded: number of oocyte retrieval cycles, number of cycle cancelations, number of oocyte retrieval failures, total number of oocytes retrieved, number of oocytes retrieved per ET cycle (±SD), total number of oocytes in metaphase II, number of oocytes in metaphase II per ET cycle (±SD), number of injected oocytes, total number of frozen embryos, number of frozen embryos per ET cycle (±SD), total number of embryos transferred, number of embryos transferred per ET cycle (±SD), and fertilization rate (%, ±SD). To evaluate differences in baseline characteristics of the patients, the following factors were compared between groups ACC-E and NC: age, etiology of infertility, body mass index (BMI), AMH level, antral follicle count (AFC), duration of infertility, and previous IVF-ET cycles. For comparison of pregnancy outcome in groups ACC-E and NC, the following factors were recorded: implantation rate, chemical pregnancy rate, clinical pregnancy rate, ongoing pregnancy rate, ectopic pregnancy rate, miscarriage rate, live birth rate, multiple pregnancy rate, birth weight (g, ± SD), gestational age at delivery (weeks, ± SD), and sex ratio. The implantation rate was defined as the number of gestational sacs divided by the number of embryos transferred. Clinical pregnancy was defined as the presence of a gestational sac with fetal heart activity. Ongoing pregnancy rates were determined as a fetus with heart beat at 12 weeks of intrauterine pregnancy. Data are expressed as mean ± SD or percentage, as appropriate. Student’s t-test, χ2 test, and Fisher’s exact test were used to determine statistical significance. A p value <0.05 was considered statistically significant. η2 and Ψ were calculated to measure the effect size. SPSS version 22 was used for statistical analysis.