Table II.
Comparison of outcomes of COS with and without letrozole.
| COS treatments in antagonist protocols, n = 380 | Letrozole-based protocols, n = 224 | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Cycle outcomes | Letrozole | No Letrozole | P-value* | Conventional start | Random start | P-value* | GnRH-agonist trigger | hCG trigger | P-value* |
| Number of cycles | 224 | 156 | 179 | 201 | 96 | 128 | |||
| Days of ovarian stimulation | 10.5 | 11.0 | 10.5 | 10.9 | 0.053 | 10.7 | 10.4 | ||
| Range | 5–18 | 7–17 | 0.03 | 5–17 | 5–18 | 6–18 | 5–18 | 0.34 | |
| Unknown | 2 | 0 | 1 | 1 | 0 | 2 | |||
| Total dose of gonadotropins | 2330 | 2064 | 0.004 | 2066 | 2359 | 0.001 | 2379 | 2294 | 0.51 |
| (IU) | 500–6750 | 800–5400 | 500–5550 | 750–6750 | 1050–6750 | 500–5850 | |||
| Range | |||||||||
| Oocytes retrieved | 12.32 | 12.21 | 0.917 | 12.3 | 12.2 | 0.79 | 13.66 | 11.32 | 0.027 |
| Range | 0–55 | 0–52 | 0–55 | 0–52 | 0–55 | 0–44 | |||
| Mature oocytes a | 8.45 | 8.52 | 0.941 | 9.1 | 7.9 | 0.197 | 9.3 | 7.6 | |
| Range | 0–46 | 0–24 | 0–44 | 0–23 | 0–44 | 0–26 | 0.14 | ||
| Unknown | 5 | 8 | 7 | 6 | 1 | 4 | |||
| Mature oocytes/total oocytes ratio a | 0.71 | 0.79 | 0.037 | 0.76 | 0.70 | 0.078 | 0.74 | 0.68 | 0.106 |
| OSI | 6.48 | 7.19 | 0.193 | 7.29 | 6.31 | 0.045 | 6.65 | 6.35 | 0.693 |
| Range | 0–45.8 | 0–31.1 | 0–45.83 | 0–22.88 | 0–26 | ||||
| Oocytes cryopreserved a | 9.7 | 10.0 | 0.81 | 10.6 | 8.97 | 0.067 | 10.4 | 9.1 | 0.252 |
| Range | 0–40 | 1–27 | 0–40 | 0–24 | 0–40 | 0–28 | |||
| Fertilization rate (%) b | 0.64 | 0.63 | 0.89 | 0.66 | 0.62 | 0.276 | 0.69 | 0.60 | 0.28 |
| Embryos cryopreserved b | 4.0 | 5.3 | 0.075 | 4.75 | 4.78 | 0.922 | 5.5 | 3.0 | 0.003 |
| Range | 0–11 | 0–29 | 0–16 | 0–29 | 0–11 | 0–9 | |||
In COS with letrozole, treatment outcomes were compared between those using GnRH agonist versus hCG trigger.
Note: data are presented as mean (range).
OSI indicates ovarian sensitivity index, the ration between oocyte yield and the dose of gonadotropins administered.
All comparisons were adjusted for age with linear regression models.
aIn total, 130 cycles in Letrozole group versus 58 cycles in No Letrozole group, 93 cycles in Conventional group versus 95 cycles in Random group and 62 cycles in GnRH agonist group versus 68 cycles in the hCG group were aimed for oocyte cryopreservation only.
bIn total, 53 cycles in Letrozole group versus 71 cycles in No Letrozole group, 59 cycles in Conventional group versus 65 cycles in Random group and 21 cycles in GnRH-agonist group versus 32 cycles in the hCG group were aimed for embryo cryopreservation only.