Table 3 Crude and adjusted odds ratio (or) for oestrogen priming of FETs and other potential confounders for cumulative live birth rate (CLBR)

Oestrogen priming in FET cycles

  Seven days

Reference

Reference

  Fourteen days

1.05 (0.90 to 1.23)

1.04 (0.89 to 1.23)

Female age at oocyte retrieval

  < 37 yrs

Reference

Reference

  ≥ 37 yrs

0.60 (0.47 to 0.76)

0.65 (0.50 to 0.83)

Body mass index (BMI)

  < 24 kg/m²

Reference

Reference

  ≥ 24 kg/m²

0.94 (0.81 to 1.10)

0.93 (0.79 to 1.09)

FSH on menstrual cycle days 2–3

  ≤ 10 mIU/ml

Reference

Reference

  > 10 mIU/ml

0.87 (0.63 to 1.21)

1.03 (0.73 to 1.45)

Anti-müllerian hormone

  < 1.2 mIU/ml

Reference

Reference

  ≥ 1.2mIU/ml

1.41 (1.11to 1.79)

1.41 (1.10 to 1.80)

Ovarian stimulation protocol

  GnRH-a long protocol

Reference

Reference

  GnRH-ant protocol

0.97 (0.79to 1.19)

1.09 (0.86 to 1.37)

Ovulation trigger

  hCG

Reference

Reference

  GnRH-a and hCG (dual trigger)

1.04 (0.76 to 1.44)

0.99 (0.69 to 1.42)

No of oocytes retrieved

  ≤ 9

Reference

Reference

  10–15

1.37 (1.09 to 1.72)

1.30 (1.02 to 1.65)

  ≥ 16

1.58 (1.28 to 1.95)

1.46 (1.17 to 1.83)

Embryo transfer stage

  D3

Reference

Reference

  D5

1.38 (1.10 to 1.74)

1.57 (1.16 to 2.13)

No of embryos transferred

  SET

Reference

Reference

  DET

0.92 (0.77 to 1.09)

1.12 (0.89 to 1.40)

Assisted hatching

  No

Reference

Reference

  Yes

1.03 (0.83 to 1.29)

0.97 (0.78 to 1.22)

Physicians of embryo transfer

  Physician A

Reference

Reference

  Physician B

1.12 (0.92 to 1.37)

1.13 (0.93 to 1.39)

  Physician C

0.93 (0.75 to 1.16)

0.95 (0.77 to 1.18)

  Physician D

1.01 (0.81 to 1.26)

1.02 (0.81 to 1.28)

Endometrial thickness prior to FET

  < 8 mm

Reference

Reference

  ≥ 8 mm

1.29 (1.00 to 1.65)

1.25 (0.97 to 1.61)