Table 4 Threshold effect analysis of the endometrial thickness on the clinical pregnancy rate

Model I (linear)

OR

95% CI

p value

Linear effect

1.058

(1.029, 1.088)

< 0.01

Model II (polyline)

OR

95% CI

p value

Predicted threshold (K, Endometrial thickness, mm)

8.4

Effect 1 (< K)

1.757

(1.494, 2.065)

< 0.01

Effect 2 (> K)

1.010

(0.979, 1.042)

0.52

variability of effectiveness

0.575

(0.483, 0.684)

Logarithmic likelihood ratio test

< 0.01