Table 6 Univariate analysis of triple line endometrium on blastocyst transfer day in FET cycles

Female age

0.972

0.882–1.070

0.559

Female BMI

1.039

0.935–1.154

0.478

Duration of infertility

0.766

0.586–1.003

0.052

Infertility type

Primary infertility

Reference

0.105

Secondary infertility

2.102

0.857–5.155

Endometrial preparation protocol

HRT

Reference

0.843

GnRHa-HRT

0.902

0.324–2.506

Serum estrogen level on the day of progesterone initiation

1.000

1.000–1.000

0.185

Serum progesterone level on the day of progesterone initiation

1.506

1.043–2.175

0.029

Serum estrogen level on the day of embryo transfer

0.999

0.999−1.000

0.024

Serum progesterone level on the day of embryo transfer

0.966

0.924–1.010

0.132