Table 1 Characteristics of included participants

Age, years, mean (SD)

33.20 (5.11)

32.33 (5.13)

31.61 (5.10)

<0.0001

Age group, n (%)

<0.0001

 <35years

598 (59.74)

1797 (66.29)

887 (72.65)

 ≥ 35years

403 (40.26)

914 (33.71)

334 (27.35)

BMI, kg/m2, mean (SD)

22.80 (2.80)

22.11 (2.85)

21.76 (2.95)

<0.0001

AMH, ng/ml, median (IQR)

2.61 (1.25 to 4.41)

2.86 (1.51 to 4.91)

3.16 (1.73 to 5.39)

<0.0001

AFC, median (IQR)

12 (7 to 16)

13 (8 to 17)

13 (9 to 18)

<0.0001

DOR, n/N (%)

223/1001 (22.28)

513/2711 (18.92)

188/1221 (15.40)

0.0002

TSH, mIU/L, median (IQR)

2.27 (1.67 to 2.95)

2.23 (1.64 to 2.96)

2.13 (1.52 to 2.81)

0.001

 <2.5 mIU/L, n (%)

597 (59.64)

1633 (60.24)

795 (65.11)

0.007

 ≥ 2.5 mIU/L, n (%)

404 (40.36)

1078 (39.76)

426 (34.89)

fT3, pmol/L, median (IQR)

4.59 (4.23 to 4.90)

4.79 (4.46 to 5.18)

4.96 (4.59 to 5.37)

<0.0001

fT4, pmol/L, median (IQR)

14.47 (13.75 to 14.97)

16.96 (16.17 to 17.79)

19.71 (19.13 to 20.62)

<0.0001

TAI, n (%)

0.4513

 Positive

157 (15.68)

381 (14.05)

175 (14.33)

 Negative

844 (84.32)

2330 (85.95)

1046 (85.67)

Infertility type, n (%)

<0.0001

 Primary

366 (36.56)

1156 (42.64)

555 (45.45)

 Secondary

635 (63.44)

1555 (57.36)

666 (54.55)

Infertility diagnosis, n (%)

0.0233

 Tubal factor

564 (56.34)

1518 (55.99)

703 (57.58)

 Diminished ovarian reserve

203 (20.28)

470 (17.34)

186 (15.23)

 Male factor

72 (7.19)

249 (9.18)

122 (9.99)

 Unexplained

33 (3.30)

112 (4.13)

60 (4.91)

 Mixed factors

129 (12.89)

362 (13.35)

150 (12.29)

Ovarian stimulation protocol, n (%)

0.0023

 Long protocol

404 (40.97)

1206 (45.00)

579 (47.93)

 Antagonist protocol

369 (37.42)

1016 (37.91)

443 (36.67)

 Mild stimulation protocol

129 (13.08)

259 (9.66)

103 (8.53)

 Other protocols

84 (8.52)

199 (7.43)

83 (6.87)

No. of aspirated oocytes, meidian (IQR)

9 (4 to 14)

10 (5 to 15)

11 (6 to 16)

<0.0001