Table 3 Relationship of risk factors with live birth by logistic regression analysis

Maternal age (years)

0.91 (0.90–0.93)

111.46

< 0.001

Maternal BMI (kg/m²)

0.98 (0.95–1.00)

4.01

0.045

Duration of infertility (years)

0.99 (0.96–1.02)

0.4

0.526

Type of infertility

 Primary

Reference

 Secondary

1.06 (0.91–1.24)

0.59

0.442

Infertility diagnosis

 Tubal

Reference

 Male

1.40 (1.07–1.82)

6.05

0.014

 Ovulatory

1.09 (0.89–1.34)

0.73

0.392

 Endometriosis

1.05 (0.79–1.40)

0.12

0.735

 Unexplained

1.09 (0.86–1.38)

0.52

0.469

 Combined

0.97 (0.71–1.34)

0.03

0.861

Ovarian stimulation protocol

 Mild stimulation

Reference

 GnRH-agonist short

1.34 (0.91–1.96)

2.17

0.141

 Progestin-primed ovarian stimulation

1.40 (0.99–1.98)

3.54

0.06

Fertilization method

 IVF

Reference

 ICSI

0.91 (0.75–1.10)

1.02

0.312

 IVF + ICSI

1.16 (0.93–1.44)

1.70

0.192

Duration of estrogen use (days)

0.96(0.94–0.99)

9.7

0.002

Endometrial thickness (mm)

1.07 (1.02–1.11)

9.77

0.002

Progesterone level on embryo transfer day (ng/mL)

 Q1 (< 7.9)

0.89 (0.75–1.04)

2.09

0.148

 Q2–Q4 (≥ 7.9)

Reference

No. of embryos transferred

 Single

Reference

 Double

2.01 (1.65–2.44)

49.13

< 0.001

Embryo stage at transfer

 Cleavage

Reference

 Blastocyst

1.54 (1.21–1.97)

11.86

0.001

Transfer of ≥ 1 top-quality embryos (%)

1.09(0.89–1.33)

0.68

0.411

Duration of embryo cryopreservation (years)

0.89 (0.75–1.06)

1.67

0.197