Table 2 Baseline clinical characteristics of the patients with RIF in the experimental and control groups

No. of previous failed cycles, median (IQR)

3 (2–4)

3 (3–4)

Age, mean ± SD, y

32.71 ± 4.14

32.90 ± 3.79

BMI, mean ± SD, kg/m²

21.38 ± 2.39

21.41 ± 1.85

Infertility duration, mean ± SD, y

5.18 ± 3.42

4.38 ± 3.29

AMH, median (IQR), ng/ml

2.86 (1.40–5.33)

4.10 (2.31–6.15)

FSH, mean ± SD, mIU/ml

6.49 ± 1.59

6.27 ± 1.67

AFC, mean ± SD

12.55 ± 6.91

13.92 ± 6.50

Endometrial thickness, mean ± SD, mm

9.47 ± 1.85

9.26 ± 1.42

P levels on the day of progesterone administration/LH peak, median (IQR), ng/ml

0.31 (0.09–0.61)

0.29 (0.15–0.72)

Types of infertility

 Primary infertility (n/%)

33 (58.9%)

41 (47.7%)

 Secondary infertility (n/%)

23 (41.1%)

45 (52.3%)

IVF indication

 Male factor (n/%)

2 (3.6%)

3 (3.5%)

 Tubal factor (n/%)

50 (89.3%)

82 (95.3%)

 PCOS (n/%)

6 (10.7%)

11 (12.8%)

 Diminished ovarian reserve (n/%)

6 (10.7%)

9 (10.5%)

 Endometriosis (n/%)

5 (8.9%)

3 (3.5%)

 Others (n/%)

2 (3.6%)

1 (1.2%)

Sampling cycle protocol

 Natural cycle (n/%)

26 (46.4%)

34 (39.5%)

 HRT cycle (n/%)

30 (53.6%)

52 (60.5%)

No. of transferred embryos, median (IQR)

2 (2–2)

2 (2–2)

Total no. of transferred embryos (n)

90

158

Embryo stage

 D3 cleavage-stage embryos (n/%)

51 (56.7%)

114 (72.2%)

 D5 or D6 blastocysts (n/%)

39 (43.3%)

44 (27.8%)