Table 1 Comparison of general characteristics and FET outcomes data between different E₂ level groups

Cases (n)

6251

3958

Baseline characteristics

Age, median (25th-75th percentiles), years

30.0 (28.0–33.0)

30.0 (28.0–34.0)

0.06

Body mass index, mean ± SD, kg/m ²

24.0 ± 3.3

24.4 ± 3.1

0.42

No. of cycles, mean ± SD

2.6 ± 0.9

2.6 ± 0.9

0.43

FET outcomes

E₂, median (25th-75th percentiles), pg/mL

193.00 (149.00-238.52)

510.07 (371.06-1473.14)

< 0.01

P, median (25th-75th percentiles), ng/mL

0.17 (0.07–0.40)

0.34 (0.16–0.59)

< 0.01

Endometrial thickness,

median (25th-75th percentiles), mm

9.50 (8.80–10.50)

9.00 (8.50–10.00)

< 0.01

No. of transfer embryos, mean ± SD

1.40 ± 0.49

1.42 ± 0.49

0.06

Transfer blastocyst rate (%)

62.3 (3896/6251)

61.5 (2436/3958)

0.43

Clinical pregnancy rate (%)

62.9 (3930/6251)

59.8 (2365/3958)

< 0.01

Implantation rate (%)

54.6 (4775/8751)

51.3 (2881/5620)

< 0.01

Miscarriage rates (%)

13.5 (529/3930)

15.6 (369/2365)

0.14

Live birth rate (%)

52.8 (3299/6251)

48.8 (1930/3958)

< 0.01