Table 1 Baseline characteristic of fresh cycles before and after matching. Values are presented as mean + standard deviation or fraction (%)

Number of cycles

731

1949

670

670

Age

31.54 ± 4.18

30.99 ± 4.01

0.003

31.51 ± 4.22

31.66 ± 4.27

0.593

Body mass index

21.91 ± 3.05

22.13 ± 3.05

0.046

21.91 ± 3.09

21.79 ± 2.97

0.645

Basal FSH (0.04%)

7.78 ± 2.63

7.57 ± 2.44

0.234

7.78 ± 2.68

7.90 ± 2.77

0.275

Antra follicle count (0.15%)

11.66 ± 6.45

13.62 ± 6.54

< 0.001

11.66 ± 6.36

11.41 ± 5.88

0.454

Anti-Mullerian hormone (0.78%)

3.13 ± 2.66

4.90 ± 3.88

< 0.001

3.19 ± 2.71

3.19 ± 2.34

0.780

Primary/secondary infertility

731

1949

0.295

670

638

0.730

primary, n%

494 (67.58)

1358 (69.68)

447 (66.57)

440 (65.67)

secondary, n%

237 (32.42)

591 (30.32)

223 (33.43)

230 (34.33)

Duration of infertility

2.91 ± 2.21

3.37 ± 2.46

< 0.001

2.99 ± 2.25

3.12 ± 2.20

0.157

Cause of infertility

ovulation disorder, n%

66 (9.03)

341 (17.50)

< 0.001

63 (7.61)

58 (8.66)

0.699

Pelvic factor, n%

339 (46.37)

920 (47.20)

0.702

307 (48.10)

305 (45.52)

0.955

Uterine factor, n%

35 (4.79)

178 (9.13)

< 0.001

35 (5.37)

45 (6.72)

0.289

Male factor, n%

194 (26.54)

589 (30.22)

0.062

185 (28.21)

175 (26.12)

0.584

Endometriosis, n%

64 (8.76)

137 (7.03)

0.131

58 (8.66)

60 (8.96)

0.923

Decreased ovarian reserve, n%

133 (18.19)

254 (13.03)

0.001

120 (17.91)

132 (19.70)

0.432

Unexplained, n%

78 (10.67)

233 (11.95)

0.355

76 (11.34)

70 (10.45)

0.653

Stimulation scheme

731

1949

< 0.001

670

670

0.799

short GnRH agonist protocol, n%

71 (9.71)

135 (6.93)

71 (10.60)

74 (11.04)

GnRH antagonist protocol, n%

483 (66.07)

669 (34.33)

422 (62.99)

427 (63.73)

long GnRH agonist protocol, n%

174 (23.81)

1130 (57.98)

174(25.96)

167 (24.93)

mild stimulation or natural cycle protocol, n%

3 (0.41)

15 (0.76)

3 (0.45)

2 (0.30)

Mean dose of Gonadotropin per day, IU

260.63 ± 65.08

245.35 ± 75.05

< 0.001

260.60 ± 66.20

263.72 ± 73.88

0.458

Endometrial thickness on the day of hCG injection, mm

11.06 ± 2.21

11.72 ± 2.51

< 0.001

11.13 ± 2.23

11.22 ± 2.39

0.724

Progesterone level on the day of hCG injection, ng/ml (0.15%)

0.73 ± 0.36

0.69 ± 0.36

0.009

0.72 ± 0.37

0.72 ± 0.39

0.716

Manner of insemination (IVF/ICSI)

731

1949

0.017

670

670

0.361

IVF, n%

471 (64,43)

1157 (59.36)

419 (62.54)

436 (65.07)

ICSI, n%

260 (35.57)

792 (40.64)

251 (37.46)

234 (34.93)

Number of embryos transferred

731

1949

0.001

638

638

0.692

1, n%

639 (87.41)

1601 (82.14)

578 (86.27)

573 (85.52)

2, n%

92 (12.59)

348 (17.86)

92 (13.73)

97 (14.48)