Table 1.

Threshold effect analysis of serum LH level (IU/L) at the hCG day on the LBR.

Outcome	Live birth
Model I (linear)	aOR	95% CI	p value
Linear effect	0.997	(0.985, 1.009)	0.647
Model II (polyline)	aOR	95% CI	p value
Predicted threshold (K, LH level, IU/L)	32
Effect 1 (<K)	1.013	(0.993, 1.033)	0.196
Effect 2 (>K)	0.961	(0.925, 0.999)	0.043
variability of effectiveness	0.366	(0.900, 0.999)	0.047
Logarithmic likelihood ratio test	0.047

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.