Table 1 Patients’ baseline characteristics

(n = 10,864)

(n = 1146)

Age (years)

31.3 ± 5.1

29.7 ± 4.5

BMI (kg/m²)

22.0 (3.0)

22.0 (4.5)

bFSH (IU/L)

7.16 (2.5)

6.57 (2.0)

Duration of infertility (years)

3 (4)

3 (3)

Primary infertility (%)

49.2

55.2

Second infertility (%)

50.8

44.8

First treatment cycle (%)

84.3

88.1

Cause of infertility (%)

tubal pathology

44.5

58.5

male factors

27.5

29.8

advanced age (≥35 years)

11.1

14.6

PCOS

6.2

11.5

endometriosis

3.5

3.3

pelvic pathology

6.5

6.5

others

3.8

4.1

unexplained factors

13.3

11.2

ART (%)

IVF

69.8

72.2

ICSI

28.8

25.6

IVF + ICSI

1.4

2.2

Stimulation protocol (%)

GnRH-a long protocol

82.8

93.5

GnRH-a prolonged (modified) protocol

11.1

5.8