Table 3.

Threshold effect analysis of serum LH level (IU/L) at the hCG day on the LBR according to differennt serum P levels.

P group	≥ 1			< 1
Model I (linear)	aOR	95% CI	p value	OR	95% CI	p value
Linear effect	1.011	(0.977, 1.045)	0.539	0.996	(0.982, 1.010)	0.564
Model II (polyline)	aOR	95% CI	p value	OR	95% CI	p value
Predicted threshold (K, LH level, IU/L)	9.6			32.0
Effect 1 (<K)	1.774	(0.750, 4.195)	0.192	1.014	(0.993, 1.035)	0.206
Effect 2 (>K)	0.991	(0.953, 1.031)	0.656	0.957	(0.917, 0.999)	0.045
variability of effectiveness	0.559	(0.233, 1.340)	0.192	0.944	(0.892, 0.999)	0.049
Logarithmic likelihood ratio test	0.051			0.049

P, progesterone; LH, luteinizing hormone; aOR, adjusted odds ratio; CI, confidence interval; K, predicted threshold.

Adjust for: female age, male age, number of transferred embryos, type of transferred embryos and endometrial thickness.