Table 2.

Subgroup analysis of melatonin concentration in maturation media.

Outcome	Variable (melatonin concentration)	Number of studies	OR (95% CI)	p value	I 2%	Q statistics (p)
NM	Low	18	1.52 (1.16,1.99)	0.002	90.8	0.00
	Moderate	17	1.19 (0.95,1.50)	0.139	82.2	0.00
	High	1	0.88 (0.57,1.37)	0.578	—	—
CR	Low	30	1.42 (1.20, 1.69)	0.00	68.3	0.00
	Moderate	19	1.14 (0.95, 1.37)	0.155	61.2	0.00
	High	4	0.91 (0.60, 1.38)	0.645	76.6	0.005
BR	Low	30	1.35 (1.18, 1.55)	0.00	54.9	0.00
	Moderate	19	1.2 (1.03, 1.40)	0.019	53.8	0.003
	High	4	1.49 (0.61, 3.63)	0.381	87.2	0.00
HBR	Low	2	1.20 (0.55, 2.59)	0.649	65.8	0.054
	Moderate	2	1.69 (1.01, 2.83)	0.045	0.0	0.595

Abbreviations: BR, blastocyst rate; CR, cleavage rate; HBR, hatched-blastocyst rate; I², heterogeneity; NM, nuclear maturation; OR, odds ratio.