Table 4 Univariate analysis for live birth rate in the entire cohort

Female age at oocyte retrieval (years)

28.26 ± 3.30

0.997 (0.97, 1.03)

0.859

Female age at embryo transfer (years)

28.76 ± 3.32

0.99 (0.96, 1.02)

0.446

BMI (kg/m²)

24.01 ± 3.57

0.93 (0.91, 0.96)

< 0.001

Infertility duration (years)

3.60 ± 2.24

0.97 (0.93, 1.01)

0.154

 primary infertility

70.70

Reference

 secondary infertility

29.30

0.95 (0.76, 1.17)

0.611^‡

AFC (n)

22.36 ± 3.36

0.97 (0.94, 0.99)

0.020

Endometrial thickness on the day of progesterone administration (mm)

9.90 ± 1.55

1.14 (1.07, 1.22)

< 0.001

 IVF

1325 (80.89%)

Reference

 ICSI

253 (15.45%)

0.77 (0.59, 1.01)

0.057^‡

  IVF + ICSI

60 (3.66%)

0.82 (0.49, 1.38)

0.450^‡

  Agonist

1489 (90.90%)

Reference

 Antagonist

145 (8.85%)

0.72 (0.51, 1.01)

0.057^‡

 Other

4 (0.24%)

0.24 (0.03, 2.34)

0.220^‡

Gonadotropin duration (days)

11.44 ± 5.41

1.002 (0.98, 1.02)

0.804

Gonadotropin dosage (IU)

2044.48 ± 922.16

0.9999 (0.9998, 1.0000)

0.147

Number of oocytes retrieved (n)

19.22 ± 8.14

1.01 (1.00, 1.02)

0.151

Number of the available embryos (n)

9.64 ± 5.12

1.03 (1.01, 1.05)

0.001

 1

431 (26.31%)

Reference

 2

1192 (72.77%)

1.46 (1.17, 1.82)

< 0.001^‡

  3

15 (0.92%)

0.86 (0.31, 2.42)

0.779^‡

  0

381 (23.26%)

Reference

  1

673 (41.09%)

1.69 (1.31, 2.18)

< 0.001^‡

  2

583 (35.59%)

3.03 (2.32, 3.97)

< 0.001^‡

  3

1 (0.06%)

0.00 (0.00, inf.)

0.970^‡

 Cleavage stage

456 (27.84%)

Reference

 Blastocyst stage

1182 (72.16%)

1.32 (1.06, 1.64)

0.013^‡

 A

178 (10.87%)

Reference

 B

1344 (82.05%)

0.97 (0.71, 1.33)

0.846^‡

 C

116 (7.08%)

0.66 (0.41, 1.06)

0.088^‡