Table 2.
Ovarian stimulation and embryo transfer (intention-to-treat analysis)
| Characteristics | Blastocyst-stage embryo transfer group (n = 497) | Cleavage-stage embryo transfer group (n = 495) | P value |
|---|---|---|---|
| Type of ovarian stimulation, No. (%) | |||
| Long GnRH Agonist suppression | 72 (14.5) | 76 (15.4) | 0.96 |
| GnRH Antagonist suppression | 214 (43.1) | 210 (42.4) | |
| Agonist flare | 30 (6.0) | 27 (5.5) | |
| Depot GnRH Agonist suppression | 181 (36.4) | 182 (36.8) | |
| Duration of ovarian stimulation, mean (SD), days | 10.2 (2.1) | 10.3 (2.1) | 0.53 |
| Total gonadotropin dose, mean (SD), IU | 1812.1 (692.0) | 1808.2 (732.0) | 0.93 |
| No of oocytes retrieved, mean (SD) | 15.0 (7.9) | 14.9 (7.4) | 0.86 |
| Estradiol level on hCG trigger day, mean (SD) [No.], pg/mL | 4444.6 (3168.5) [496] | 4278.0 (2685.9) [495] | 0.37 |
| Progesterone level on hCG trigger day, mean (SD) [No.], ng/mL | 1.3 (1.4) [494] | 1.2 (0.8) [495] | 0.34 |
| ICSI for insemination, No. (%) | 125 (25.2) | 126 (25.5) | 0.91 |
| No of viable embryos on day 2–3, mean (SD) | 8.8 (4.6) | 8.5 (4.4) | 0.32 |
| No of good-quality embryos on day 2–3, mean (SD) | 6.2 (3.9) | 6.1 (3.7) | 0.73 |
| No of viable embryos on day 5–6, mean (SD) | 5.6 (3.4) | - | - |
| No of good-quality embryos on day 5–6, mean (SD) | 3.7 (2.9) | - | - |
| First transfer (fresh), No. (%) | 264 (53.1)a | 272 (54.9)b | 0.56 |
| Freeze-only, No. (%)c | 227 (45.7) | 223 (45.1) | 0.84 |
| Reasons for Freeze-only, No. (%) | |||
| Endometrial factor | 8/227 (3.5) | 15/223 (6.7) | 0.28 |
| Risk of OHSS | 167/227 (73.6) | 164/223 (73.5) | |
| High progesterone | 29/227 (12.8) | 29/223 (13.0) | |
| Other | 23/227 (10.1) | 15/223 (6.7) | |
| No embryo transfers, No. (%) | 11 (2.2) | 4 (0.8) | 0.07 |
| Reasons for no-transfer, No. (%) | |||
| No embryo available | 7/11 (63.6)d | 0 | 0.056 |
| Natural conception after oocyte retrieval | 2/11 (18.2) | 3/4 (75.0) | |
| Personal issue | 1/11 (9.1) | 1/4 (25.0) | |
| Endometrial factor | 1/11 (9.1) | 0 | |
| No of embryo transfers, No. (%)e | 727 | 875 | |
| First transfers | 486/727 (66.9) | 491/875 (56.1) | 1.44e-06 |
| Second transfers | 189/727 (26.0) | 261/875 (29.8) | |
| Third transfers | 52/727 (7.2) | 123/875 (14.1) | |
| No of embryos transferred, No. (%)e | |||
| One embryo | 709/727 (97.5) | 842/875 (96.2) | 0.14 |
| Two embryos | 18/727(2.5) | 33/875 (3.8) | |
| Stage of embryo transferred, No. (%)e | |||
| Blastocyst-stage embryo transfer | 719/727 (98.9) | 42/875 (4.8)f | 1.46e-308 |
| Cleavage-stage embryo transfer | 8/727 (1.1) | 833/875 (95.2) | |
| Moderate or severe OHSS, No. (%) | 23 (4.6) | 17 (3.4) | 0.34 |
GnRH gonadotropin-releasing hormone, hCG human chorionic gonadotropin, ICSI intracytoplasmic sperm injection, OHSS ovarian hyperstimulation syndrome, SD standard deviation.
Two-sided P values. No adjustments were made for multiple comparisons. A two-sample t-test was used for continuous variables; Chi-square test or Fisher’s Exact Test was used for categorical data.
a12 participants underwent fresh blastocyst transfer on day 6.
bOnly 7 participants underwent embryo transfer on day 2, all occurring in fresh transfer cycle at one study site, due to their work schedules.
cWomen who underwent freeze-only had all embryos frozen in the fresh cycle of ovarian stimulation for risk of OHSS or other reasons. Six participants in the blastocyst group did not have any embryos available for transfer and freezing.
dFive participants had no blastocyst-stage embryos after extended culture and no embryos transferred; 1 participant had no embryos but was randomized; 1 participant had 1 blastocyst frozen after freeze-only strategy, but the blastocyst did not survive after thawing.
eCalculated based on the total number of embryo transfer cycles.
f One participant underwent sequential transfer (transfer of one cleavage-stage and one blastocyst-stage embryo in one frozen embryo transfer cycle).