Table 2.
Characteristics of Cycles by Progesterone Category and Ovarian Stimulation Medication
| Clomiphene, Letrozole, and Gonadotropin Cycles (n = 2376) | P Value | Clomiphene and Letrozole Cycles (n = 1671) | P Value | Gonadotropin Cycles (n = 705) | P Value | ||||
|---|---|---|---|---|---|---|---|---|---|
| Progesterone group, n cyclesa | Low | Normal | Low | Normal | Low | Normal | |||
| 238 | 2138 | 167 | 1504 | 71 | 634 | ||||
| Age | 32.7 (4.3) | 32.2 (4.2) | 0.031 | 32.9 (4.4) | 32.1 (4.2) | 0.019 | 32.4 (4.1) | 32.4 (4.0) | 0.716 |
| BMI | 31.4 (8.4) | 26.7 (6.5) | <0.001 | 32.0 (8.9) | 26.9 (6.5) | <0.001 | 30.0 (7.1) | 26.3 (6.3) | <0.001 |
| No. of follicles ≥16 mm | 1.6 (0.8) | 2.0 (1.1) | <0.001 | 1.5 (0.7) | 1.9 (0.9) | <0.001 | 1.9 (1.1) | 2.2 (1.5) | 0.058 |
| Follicular phase length | 12.8 (2.6) | 12.0 (2.0) | <0.001 | 12.9 (2.5) | 12.0 (1.9) | <0.001 | 12.6 (2.7) | 11.9 (2.3) | 0.005 |
| AMH, ng/mL | 2.3 (1.7) | 2.6 (2.0) | 0.115 | 2.3 (1.8) | 2.6 (2.1) | 0.071 | 2.3 (1.5) | 2.5 (2.0) | 0.957 |
| Duration of infertility, mo | 37.9 (25.0) | 34.7 (25.4) | 0.022 | 36.8 (24.6) | 34.5 (25.0) | 0.193 | 40.3 (26.0) | 35.2 (26.4) | 0.028 |
| Peak estradiol, pg/mL | 357.4 (353.4) | 507.6 (443.7) | <0.001 | 258.4 (239.0) | 405.8 (370.1) | <0.001 | 588.9 (457.0) | 747.9 (506.4) | 0.002 |
| Peak estradiol/follicle ≥16 mm | 229.6 (178.3) | 277.8 (241.6) | 0.064 | 189.1 (143.3) | 229.1 (206.6) | 0.088 | 326.4 (214.1) | 393.3 (277.0) | 0.059 |
| Medication dose | |||||||||
| Clomiphene, mg | 572.3 (132.6) | 532.9 (110.4) | 0.001 | 572.3 (132.6) | 532.9 (110.4) | 0.001 | NA | NA | NA |
| Letrozole, mg | 28.6 (6.0) | 28.3 (6.0) | 0.439 | 28.6 (6.0) | 28.3 (6.0) | 0.439 | NA | NA | NA |
| Gonadotropins, IU | 788.0 (642.0) | 635.2 (385.1) | 0.049 | NA | NA | NA | 788.0 (642.0) | 635.2 (385.1) | 0.049 |
| Day of progesteroneb | 8.6 (0.9) | 8.7 (0.8) | 0.117 | 8.8 (0.9) | 8.7 (0.8) | 0.728 | 8.3 (0.8) | 8.7 (0.8) | 0.001 |
| Achieved pregnancy, n (%) | 12 (5.0) | 279 (13.1) | <0.001 | 6 (3.6) | 164 (10.9) | 0.003 | 6 (8.5) | 115 (18.1) | 0.040 |
| Clinical pregnancy, n (%) | 9 (3.8) | 194 (9.1) | 0.006 | 3 (1.8) | 114 (7.6) | 0.005 | 6 (8.5) | 80 (12.6) | 0.309 |
| Live birth, n (%) | 9 (3.8) | 192 (9.0) | 0.006 | 3 (1.8) | 113 (7.5) | 0.003 | 6 (8.5) | 79 (12.5) | 0.325 |
Values are expressed as means (SD) unless otherwise indicated. Comparisons between groups are by parametric or nonparametric tests as appropriate. Age, BMI, AMH, and duration of infertility are baseline characteristics. Other variables are cycle specific.
Abbreviation: NA, not applicable.
Cutpoints to define “low” vs “normal” midluteal progesterone cycles were the 10th percentile; cutpoints were consistent with the efficiency curves for each treatment group independently. Cutpoints were 15.8, 14.8, and 9.1 ng/mL for clomiphene, letrozole, and gonadotropin cycles, respectively.
Day of progesterone is the interval between the day of the progesterone blood draw and the hCG injection.