Table 1 Baseline characteristics of the study participants

Age

38.0 (22–48)

37.0 (22–48)

38.4 (25–48)

< 0.001

BMI (kg/m2)

22.0 (0–38.6)

21.8 (0–37.4)

22.3 (16.9–38.6)

< 0.05

AMH (ng/mL)

2.48 (0.02–46.1)

3.2 (0–18.5)

3.00 (0.05–17.3)

< 0.01

Basal FSH (mIU/mL)

7.0 (0–31.2)

6.9 (0–31.2)

7.2 (0.4–25.6)

N.S

Basal LH (mIU/mL)

4.6 (0–14.8)

4.6 (0–14.8)

4.9 (0–14.5)

N.S

Basal E2 (pg/mL)

33.5 (0–98.4)

33.4 (0–98.4)

34.4 (0–92.2)

N.S

Endometrial thickness (mm)

9.9 (6.2–20.2)

9.9 (6.2–20.2)

9.8 (7.2–17.2)

N.S

Serum E2 value on ET day (pg/mL)

227 (10–1,745)

224 (10–1,745)

234 (26.7–1,585)

N.S

Serum P4 value on ET day (ng/mL)

12.6 (0.11–81.2)

12.7 (1.5–81.2)

12.8 (1.24–34.7)

N.S

Number of natural cycles/hormone replacement therapy cycles (n)

89/1,242

70/1,056

19/186

N.S

GQB (%[n])

75.1 (999)

79.4 (894)

51.2 (105)

< 0.001

Blastocyst shrinkage at 2–11 min after warming (%[n])

19.9 (265)

7.6 (86)

87.3 (179)

< 0.001

Assisted hatching (%[n])

89.0 (1,183)

88.3 (993)

93.2 (191)

< 0.05

Hyaluronic acid-enriched transfer medium

2.7 (36)

2.7 (30)

2.9 (6)

N.S

Infertility causes (total number of causes)

1,484

1,260

438

 Male factor

514 (34.6%)

430 (34.1%)

84 (37.5%)

N.S

 Tubal factor

101 (6.8%)

89 (7.1%)

12 (5.4%)

N.S

 Cervical factor

16 (1.1%)

15 (1.2%)

1 (0.45%)

N.S

 Endometriosis

72 (4.9%)

59 (4.7%)

13 (5.8%)

N.S

 Polycystic ovarian syndrome

58 (3.9%)

52 (4.1%)

6 (2.7%)

N.S

 Thyroid dysfunction

38 (2.6%)

34 (2.7%)

4 (1.8%)

N.S

 Hyperprolactinemia

4 (0.27%)

2 (0.16%)

2 (0.89%)

N.S

 Anti-sperm-antibodies

12 (0.81%)

12 (0.95%)

0 (0%)

N.S

 Uterine fibroid

48 (3.2%)

42 (3.3%)

6 (2.7%)

N.S

 Adenomyosis

5 (0.34%)

5 (0.40%)

0 (0%)

N.S

 Uterine malformation

30 (2.0%)

25 (2.0%)

5 (2.2%)

N.S

 Diminished ovarian reserve

133 (9.0%)

109 (8.7%)

24 (10.7%)

N.S

 Oncofetility

14 (0.94%)

14 (1.1%)

0 (0%)

N.S

 Unexplained infertility

438 (29.5%)

371 (29.4%)

67 (29.9%)

N.S