Table 1 Baseline characteristics according to endometrial thickness at trigger day
|  | ≤7.6 mm (n = 109) | 7.7–13.0 mm (n = 798) | ≥13.1 mm (n = 109) | P-value |
|---|---|---|---|---|
Maternal age (years) | 30.7 ± 3.7 | 30.2 ± 3.7 | 30.0 ± 3.3 | 0.313 |
Maternal BMI (kg/m2) | 21.76 ± 2.56 | 22.34 ± 3.35 | 22.13 ± 2.87 | 0.401 |
Paternal age (years) | 32.9 ± 5.4 | 32.1 ± 4.4 | 32.1 ± 4.9 | 0.465 |
Paternal BMI (kg/m2) | 25.09 ± 2.95 | 24.50 ± 3.08 | 24.35 ± 3.21 | 0.224 |
Nulligravida, n (%) | 53 (48.6) | 551 (69.0) | 90 (82.6) | < 0.001 |
Nulliparity, n (%) | 101 (92.7) | 761 (95.4) | 103 (94.5) | 0.465 |
Duration of infertility (years) | 2.8 ± 1.8 | 2.9 ± 2.0 | 3.0 ± 2.2 | 0.828 |
Infertility diagnosis, n (%) | Â | Â | Â | 0.610 |
 Anovulation | 19 (17.4) | 143 (17.9) | 16 (14.7) |  |
 Male factor | 21 (19.3) | 192 (24.1) | 28 (25.7) |  |
 Endometriosis | 0 (0) | 18 (2.3) | 3 (2.8) |  |
  Mixed | 3 (2.8) | 26 (3.3) | 5 (4.6) |  |
 Unexplained | 66 (60.6) | 419 (52.5) | 57 (52.3) |  |
Rank of IUI attempts, n (%) | Â | Â | Â | 0.652 |
 1st cycle | 70 (64.2) | 485 (60.8) | 61 (56.0) |  |
 2nd cycle | 30 (27.5) | 246 (30.8) | 35 (32.1) |  |
 3rd or more | 9 (8.3) | 67 (8.4) | 13 (11.9) |  |
Stimulation protocol, n (%) | Â | Â | Â | 0.661 |
 LE | 13 (11.9) | 79 (9.9) | 9 (8.3) |  |
 LE + hMG | 96 (88.1) | 719 (90.1) | 100 (91.7) |  |
Length of treatment (days) | 10.3 ± 2.0 | 11.5 ± 2.9 | 12.5 ± 2.7 | < 0.001 |
Peak E2 level (pg/mL) | 256.6 ± 197.9 | 287.9 ± 205.8 | 346.3 ± 248.7 | < 0.001 |
Endometrial thickness (mm) | 6.60 ± 0.96 | 10.06 ± 1.43 | 14.42 ± 1.27 | < 0.001 |
Postprocessing TMSC (millions) | 27.8 ± 27.4 | 32.6 ± 37.4 | 33.2 ± 33.8 | 0.430 |
Vanishing twin syndrome, n (%) | 4 (3.7) | 15 (1.9) | 2 (1.8) | 0.469 |
Pregnancy complications, n (%) | 7 (6.4) | 60 (7.5) | 9 (8.3) | 0.875 |
Year of treatment | Â | Â | Â | 0.131 |
 2008–2011 | 6 (5.5) | 72 (9.0) | 14 (12.8) |  |
 2012–2015 | 39 (35.8) | 345 (43.2) | 43 (39.4) |  |
 2016–2018 | 64 (58.7) | 381 (47.7) | 52 (47.7) |  |